Co-reporter:Zhigang Xie, Cheng Wang, Kathryn E. deKrafft, and Wenbin Lin
Journal of the American Chemical Society February 23, 2011 Volume 133(Issue 7) pp:2056-2059
Publication Date(Web):January 28, 2011
DOI:10.1021/ja109166b
Porous cross-linked polymers (PCPs) with phosphorescent [Ru(bpy)3]2+ and [Ir(ppy)2(bpy)]+ building blocks were obtained via octacarbonyldicobalt (Co2(CO)8)-catalyzed alkyne trimerization reactions. The resultant Ru- and Ir-PCPs exhibited high porosity with specific surface areas of 1348 and 1547 m2/g, respectively. They are thermally stable at up to 350 °C in air and do not dissolve or decompose in all solvents tested, including concentrated hydrochloric acid. The photoactive PCPs were shown to be highly effective, recyclable, and reusable heterogeneous photocatalysts for aza-Henry reactions, α-arylation of bromomalonate, and oxyamination of an aldehyde, with catalytic activities comparable to those of the homogeneous [Ru(bpy)3]2+ and [Ir(ppy)2(bpy)]+ photocatalysts. This work highlights the potential of developing photoactive PCPs as highly stable, molecularly tunable, and recyclable and reusable heterogeneous photocatalysts for a variety of important organic transformations.
Co-reporter:Michaël Carboni, Carter W. Abney, Shubin Liu and Wenbin Lin
Chemical Science 2013 vol. 4(Issue 6) pp:2396-2402
Publication Date(Web):04 Apr 2013
DOI:10.1039/C3SC50230A
Three metal–organic frameworks (MOFs) of the UiO-68 network topology were prepared using the amino-TPDC or TPDC bridging ligands containing orthogonal phosphorylurea groups (TPDC is p,p′-terphenyldicarboxylic acid), and investigated for sorption of uranium from water and artificial seawater. The stable and porous phosphorylurea-derived MOFs were shown to be highly efficient in sorbing uranyl ions, with saturation sorption capacities as high as 217 mg U g−1 which is equivalent to binding one uranyl ion for every two sorbent groups. Coordination modes between uranyl groups and simplified phosphorylurea motifs were investigated by DFT calculations, revealing a thermodynamically favorable monodentate binding of two phosphorylurea ligands to one uranyl ion. Convergent orientation of phosphorylurea groups at appropriate distances inside the MOF cavities is believed to facilitate their cooperative binding with uranyl ions. This work represents the first application of MOFs as novel sorbents to extract actinide elements from aqueous media.
Co-reporter:Rachel C. Huxford-Phillips, Shane R. Russell, Demin Liu and Wenbin Lin
RSC Advances 2013 vol. 3(Issue 34) pp:14438-14443
Publication Date(Web):06 Jun 2013
DOI:10.1039/C3RA42033G
Nanoscale coordination polymers (NCPs) containing a Pt(IV) cisplatin prodrug, disuccinatocisplatin, were formed by a surfactant-templated synthesis and were shown to have a prodrug loading of 8.2 wt% and a diameter of ∼133 nm by dynamic light scattering. These NCPs were stabilized by coating with a DOPC/cholesterol/DSPE-Peg2 K lipid layer; a release profile in phosphate buffered saline showed an initial drug release of ∼25% within the first hour and no more release observed up to 192 h. The NCP was rendered target-specific for sigma receptors by addition of a DSPE–Peg2 K–AA conjugate (AA = anisamide) in the lipid formulation. The AA-containing NCP showed a statistically significant decrease in IC50 (inhibitory concentration, 50%) compared to the non-targeted NCP. Enhanced uptake of the AA-containing NCP was further supported by confocal microscopy and competitive binding assays.
Co-reporter:Juan L. Vivero-Escoto, Michaël Carboni, Carter W. Abney, Kathryn E. deKrafft, Wenbin Lin
Microporous and Mesoporous Materials 2013 180() pp: 22-31
Publication Date(Web):
DOI:10.1016/j.micromeso.2013.05.030
Co-reporter:Cheng Wang, Teng Zhang, and Wenbin Lin
Chemical Reviews 2012 Volume 112(Issue 2) pp:1084
Publication Date(Web):November 9, 2011
DOI:10.1021/cr200252n
Co-reporter:Juan L. Vivero-Escoto, Rachel C. Huxford-Phillips and Wenbin Lin
Chemical Society Reviews 2012 vol. 41(Issue 7) pp:2673-2685
Publication Date(Web):10 Jan 2012
DOI:10.1039/C2CS15229K
Nanoparticle-based contrast agents are attracting a great deal of attention for various biomedical imaging and theranostic applications. Compared to conventional contrast agents, nanoparticles possess several potential advantages to improve in vivo detection and to enhance targeting efficiency. Silica-based nanoprobes can be engineered to achieve longer blood circulation times, specific clearance pathways, and multivalent binding. In this tutorial review, we summarize the latest progress on designing silica-based nanoprobes for imaging and theranostic applications. The synthesis of both solid silica and mesoporous silica nanoparticles is described, along with different approaches used for surface functionalization. Special emphasis is placed on the application of silica-based nanoprobes in optical, magnetic resonance, and multimodal imaging. The latest breakthroughs in the applications of silica nanoparticles as theranostic agents are also highlighted.
Co-reporter:Kathryn E. deKrafft;Cheng Wang
Advanced Materials 2012 Volume 24( Issue 15) pp:2014-2018
Publication Date(Web):
DOI:10.1002/adma.201200330
Co-reporter:Caleb A. Kent ; Demin Liu ; Thomas J. Meyer
Journal of the American Chemical Society 2012 Volume 134(Issue 9) pp:3991-3994
Publication Date(Web):February 13, 2012
DOI:10.1021/ja211271m
Amplified luminescence quenching has been demonstrated in metal–organic frameworks (MOFs) composed of Ru(II)-bpy building blocks with long-lived, largely triplet metal-to-ligand charge-transfer excited states. Strong non-covalent interactions between the MOF surface and cationic quencher molecules coupled with rapid energy transfer through the MOF microcrystal facilitates amplified quenching with a 7000-fold enhancement of the Stern–Völmer quenching constant for methylene blue compared to a model complex.
Co-reporter:Cheng Wang ; Kathryn E. deKrafft
Journal of the American Chemical Society 2012 Volume 134(Issue 17) pp:7211-7214
Publication Date(Web):April 9, 2012
DOI:10.1021/ja300539p
Pt nanoparticles of 2–3 nm and 5–6 nm in diameter were loaded into stable, porous, and phosphorescent metal–organic frameworks (MOFs 1 and 2) built from [Ir(ppy)2(bpy)]+-derived dicarboxylate ligands (L1 and L2) and Zr6(μ3-O)4(μ3-OH)4(carboxylate)12 secondary building units, via MOF-mediated photoreduction of K2PtCl4. The resulting Pt@MOF assemblies serve as effective photocatalysts for hydrogen evolution by synergistic photoexcitation of the MOF frameworks and electron injection into the Pt nanoparticles. Pt@2 gave a turnover number of 7000, approximately five times the value afforded by the homogeneous control, and could be readily recycled and reused.
Co-reporter:Marcela M. Wanderley ; Cheng Wang ; Chuan-De Wu
Journal of the American Chemical Society 2012 Volume 134(Issue 22) pp:9050-9053
Publication Date(Web):May 18, 2012
DOI:10.1021/ja302110d
A highly porous and fluorescent metal–organic framework (MOF), 1, was built from a chiral tetracarboxylate bridging ligand derived from 1,1′-bi-2-naphthol (BINOL) and a cadmium carboxylate infinite-chain secondary building unit. The fluorescence of 1 can be effectively quenched by amino alcohols via H-bonding with the binaphthol moieties decorating the MOF, leading to a remarkable chiral sensor for amino alcohols with greatly enhanced sensitivity and enantioselectivity over BINOL-based homogeneous systems. The higher detection sensitivity of 1 is due to a preconcentration effect by which the analytes are absorbed and concentrated inside the MOF channels, whereas the higher enantioselectivity of 1 is believed to result from enhanced chiral discrimination owing to the cavity confinement effect and the conformational rigidity of the BINOL groups in the framework. 1 was quenched by four chiral amino alcohols with unprecedentedly high Stern–Volmer constants of 490–31200 M–1 and enantioselectivity ratios of 1.17–3.12.
Co-reporter:Cheng Wang ; Jin-Liang Wang
Journal of the American Chemical Society 2012 Volume 134(Issue 48) pp:19895-19908
Publication Date(Web):November 8, 2012
DOI:10.1021/ja310074j
As a new class of porous, crystalline, molecular materials, metal–organic frameworks (MOFs) have shown great promise as recyclable and reusable single-site solid catalysts. Periodic order and site isolation of the catalytic struts in MOFs facilitate the studies of their activities and reaction mechanisms. Herein we report the construction of two highly stable MOFs (1 and 2) using elongated dicarboxylate bridging ligands derived from Cp*Ir(L)Cl complexes (L = dibenzoate-substituted 2,2′-bipyridine, bpy-dc, or dibenzoate-substituted 2-phenylpyridine, ppy-dc) and Zr6O4(OH)4(carboxylate)12 cuboctahedral secondary building units (SBUs) and the elucidation of water oxidation pathways of the Cp*Ir(L)Cl catalysts using these MOFs. We carried out detailed kinetic studies of Ce4+-driven water oxidation reactions (WORs) catalyzed by the MOFs using UV–vis spectroscopy, phosphorescent oxygen detection, and gas chromatographic analysis. These results confirmed not only water oxidation activity of the MOFs but also indicated oxidative degradation of the Cp* rings during the WOR. The (bpy-dc)Ir(H2O)2XCl (X is likely a formate or acetate group) complex resulted from the oxidative degradation process was identified as a competent catalyst responsible for the water oxidation activity of 1. Further characterization of the MOFs recovered from WORs using X-ray photoelectron, diffuse-reflectance UV–vis absorption, luminescence, and infrared spectroscopies supported the identity of (bpy-dc)Ir(H2O)2XCl as an active water oxidation catalyst. Kinetics of MOF-catalyzed WORs were monitored by Ce4+ consumptions and fitted with a reaction–diffusion model, revealing an intricate relationship between reaction and diffusion rates. Our work underscores the opportunity in using MOFs as well-defined single-site solid catalytic systems to reveal mechanistic details that are difficult to obtain for their homogeneous counterparts.
Co-reporter:Demin Liu, Haohan Wu, Shunzhi Wang, Zhigang Xie, Jing Li and Wenbin Lin
Chemical Science 2012 vol. 3(Issue 10) pp:3032-3037
Publication Date(Web):09 Jul 2012
DOI:10.1039/C2SC20601C
A 6,8-connected 3-dimensional metal–organic framework (2) of the tph topology was constructed from a new aromatic-rich, tetraphenylmethane-derived octa-carboxylate bridging ligand and trizinc cluster secondary building units (SBUs), and exhibited exceptionally high hydrogen (58 mg g−1 and 39 g L−1 at 52 bar and 77 K) and methane (276 mg g−1 and 189 g L−1 at 80 bar and 298 K) uptake capacities. 2 has the highest hydrogen uptake at 298 K among all of the MOFs that have been examined to date. The gravimetric and volumetric methane uptake capacities for 2 are the highest among thousands of MOFs that have been evaluated. We attribute the exceptionally high gas uptake capacities of 2 to the highly branched, aromatic-rich nature of the bridging ligand, optimal pore size, and the open metal sites in the trizinc SBUs in a stable high-connectivity MOF.
Co-reporter:Jin-Liang Wang, Cheng Wang, Kathryn E. deKrafft, and Wenbin Lin
ACS Catalysis 2012 Volume 2(Issue 3) pp:417
Publication Date(Web):February 7, 2012
DOI:10.1021/cs300027n
Phosphorescent cross-linked polymers 1 and 2 were synthesized via oxidative homocoupling reactions of tetra(ethynyl) derivatives of Ru(bpy)32+ (with the alkynyl groups located at 4,4′- or 5,5′- positions of two substituted bipyridines). These cross-linked polymer particles contain exceptionally high Ru(bpy)32+ loadings and serve as highly efficient and reusable heterogeneous photocatalysts for a range of organic transformations, presumably owing to the ability of the Ru(bpy)32+ moieties in the polymer network to transport triplet excited states to particle surfaces to initiate the organic reactions. This work illustrates the potential of developing photocatalytic cross-linked polymers from photoactive molecular building blocks for solar energy utilization.Keywords: cross-linked polymer; energy transfer; excited state migration; heterogeneous catalysis; light-harvesting; photocatalysis;
Co-reporter:Rachel C. Huxford, Kathryn E. deKrafft, William S. Boyle, Demin Liu and Wenbin Lin
Chemical Science 2012 vol. 3(Issue 1) pp:198-204
Publication Date(Web):20 Oct 2011
DOI:10.1039/C1SC00499A
Nanoscale coordination polymers (NCPs) have been demonstrated as an interesting platform for drug delivery, as they possess many advantages over small-molecule chemotherapeutics such as high payloads, lower systemic toxicity, tunability, and enhanced tumor uptake. Existing formulations for the delivery of methotrexate (MTX), an antifolate cancer drug, have very low drug loadings. Herein, we report the incorporation of MTX as a building block in an NCP formulation with exceptionally high drug loadings (up to 79.1 wt%) and the selective delivery of the NCP to cancer cells. Encapsulation of the NCP in a functionalized lipid bilayer allows for targeted delivery and controlled release to cancer cells. A phosphor can be doped into the NCPs for monitoring particle uptake by optical imaging. The lipid-coated and anisamide-targeted NCPs have superior in vitro efficacy against acute lymphoblastic leukemia cells when compared to the free drug.
Co-reporter:Jin-Liang Wang, Cheng Wang, and Wenbin Lin
ACS Catalysis 2012 Volume 2(Issue 12) pp:2630
Publication Date(Web):October 24, 2012
DOI:10.1021/cs3005874
Metal–organic frameworks (MOFs), a new class of crystalline molecular solids built from linking organic ligands with metal or metal-cluster connecting points, have recently emerged as a versatile platform for developing single-site solid catalysts. MOFs have been used to drive a range of reactions, including Lewis acid/base catalyzed reactions, redox reactions, asymmetric reactions, and photocatalysis. MOF catalysts are easily separated from the reaction mixtures for reuse, and yet their molecular nature introduces unprecedented chemical diversity and tunability to drive a large scope of catalytic reactions. This Perspective aims to summarize recent progress on light harvesting and photocatalysis with MOFs. The charge-separated excited states of the chromophoric building blocks created upon photon excitation can migrate over long distances to be harvested as redox equivalents at the MOF/liquid interfaces via electron transfer reactions or can directly activate the substrates that have diffused into the MOF channels for photocatalytic reactions. MOF-catalyzed and photodriven proton reduction, CO2 reduction, and organic transformations will be discussed in this Perspective.Keywords: CO2 reduction; light harvesting; metal−organic frameworks; photocatalysis; water splitting
Co-reporter:Liang Wen, Peng Cheng and Wenbin Lin
Chemical Science 2012 vol. 3(Issue 7) pp:2288-2292
Publication Date(Web):23 Apr 2012
DOI:10.1039/C2SC20172K
Two high-connectivity MOFs with very interesting modes of mixed-motif interpenetration and cross-linking were synthesized using the elongated and aromatic-rich methanetetra(biphenyl-p-carboxylic acid) bridging ligand (H4MTBPC, H4L). [Zn4(L)(H2L)2]·12DEF·40H2O (1) contains an interpenetrating 4,8-connected 3D framework of the alb/P topology and 4,4-connected 3D network of the lon topology, whereas [Co5(L)(HL)2]·15DMF·37H2O (2) is the first 4,12-connected 4-nodal net with the Schläfli symbol of {422.639.85}{45.6}2{46}. The structure of 2 can be visualized as cross-linking of three 4,4-connected 3D networks of the lon topology. The seemingly different structures of 1 and 2 are in fact closely related as the structure of 1 can be obtained by removing one of the Co centers in the penta-cobalt secondary building unit (SBU). Unusual mixed-motif interpenetration in 1 and cross-linking in 2 rigidify and stabilize the frameworks, leading to highly porous MOFs with high uptake capacities for H2 and CO2.
Co-reporter:Kathryn E. deKrafft, William S. Boyle, Laurel M. Burk, Otto Z. Zhou and Wenbin Lin
Journal of Materials Chemistry A 2012 vol. 22(Issue 35) pp:18139-18144
Publication Date(Web):07 Jun 2012
DOI:10.1039/C2JM32299D
Nanoscale metal–organic frameworks (NMOFs) of the UiO-66 structure containing high Zr (37 wt%) and Hf (57 wt%) content were synthesized and characterized, and their potential as contrast agents for X-ray computed tomography (CT) imaging was evaluated. Hf-NMOFs of different sizes were coated with silica and poly(ethylene glycol) (PEG) to enhance biocompatibility, and were used for in vivo CT imaging of mice, showing increased attenuation in the liver and spleen.
Co-reporter:Joseph M. Falkowski, Sophie Liu, Cheng Wang and Wenbin Lin
Chemical Communications 2012 vol. 48(Issue 52) pp:6508-6510
Publication Date(Web):08 May 2012
DOI:10.1039/C2CC32232C
A pair of interpenetrated and non-interpenetrated chiral metal–organic frameworks with the same catalytic sites but different open channel sizes catalysed asymmetric cyclopropanation of substituted terminal alkenes with excellent diastereoselectivities (up to 9.6) and enantioselectivities (up to >99%).
Co-reporter:Teng Zhang, Feijie Song and Wenbin Lin
Chemical Communications 2012 vol. 48(Issue 70) pp:8766-8768
Publication Date(Web):13 Jul 2012
DOI:10.1039/C2CC34033J
Chiral metal–organic frameworks built from a Co-salen derived dicarboxylate bridging ligand exhibited different regioselectivities from the corresponding homogeneous catalyst by shutting down bimolecular activation pathways.
Co-reporter:Demin Liu, Stephanie A. Kramer, Rachel C. Huxford-Phillips, Shunzhi Wang, Joseph Della Rocca and Wenbin Lin
Chemical Communications 2012 vol. 48(Issue 21) pp:2668-2670
Publication Date(Web):23 Jan 2012
DOI:10.1039/C2CC17635A
Nanoscale coordination polymers containing exceptionally high loadings of bisphosphonates were coated with single lipid bilayers to control the drug release kinetics and functionalized with a targeting ligand to endow cell-targeting capability, leading to much enhanced cytotoxicity against human lung and pancreatic cancer cells.
Co-reporter:Liang Wen, Peng Cheng and Wenbin Lin
Chemical Communications 2012 vol. 48(Issue 23) pp:2846-2848
Publication Date(Web):27 Jan 2012
DOI:10.1039/C2CC17298D
Exposure to CH2Cl2 at room temperature induces single-crystal to single-crystal transformation of the 2D coordination network [Zn2L(DMF)4]·2DMF·4H2O to the 3D metal–organic framework [Zn2L(H2O)2]·xsolv viadimerization of the metal-connecting points, leading to significant enhancement in framework stability, porosity, and H2 uptake capacity.
Co-reporter:Cheng Wang, Zhigang Xie, Kathryn E. deKrafft, and Wenbin Lin
ACS Applied Materials & Interfaces 2012 Volume 4(Issue 4) pp:2288
Publication Date(Web):March 12, 2012
DOI:10.1021/am3003445
Nonporous, phosphorescent cross-linked polymers (Ru-CP and Ir-CP) were synthesized via Pd-catalyzed Sonogashira cross-coupling reactions between tetra(p-ethynylphenyl)methane and dibrominated Ru(bpy)32+ or Ir(ppy)2(bpy)+, respectively. The resultant particulate cross-linked polymer (CP) materials have very high catalyst loadings (76.3 wt % for Ru-CP and 71.6 wt % for Ir-CP), and are nonporous with negligibly small surface areas (2.9 m2/g for Ru-CP and 2.7 m2/g for Ir-CP). Despite their nonporous nature, the insoluble CP materials serve as highly active and recyclable heterogeneous photocatalysts for a range of organic transformations such as aza-Henry reaction, aerobic amine coupling, and dehalogenation of benzyl bromoacetate. An efficient light-harvesting mechanism, which involves collection of photons by exciting the 3MLCT states of the phosphors and migration of the excited states to the particle surface, is proposed to account for the very high catalytic activities of these nonporous CPs. Steady-state and time-resolved emission data, as well as the reduced catalytic activity of Os(bpy)32+-doped Ru-CPs supports efficient excited state migration for the CP frameworks. This work uncovers a new strategy in designing highly efficient photocatalysts based on light-harvesting cross-linked polymers.Keywords: artificial photosynthesis; cross-linked polymer; energy transfer; excited-state migration; light-harvesting; photocatalysis;
Co-reporter:Kathryn E. deKrafft, Cheng Wang, Zhigang Xie, Xin Su, Bruce J. Hinds, and Wenbin Lin
ACS Applied Materials & Interfaces 2012 Volume 4(Issue 2) pp:608
Publication Date(Web):January 31, 2012
DOI:10.1021/am2018095
Hydrogen production from water splitting provides a potential solution to storing harvested solar energy in chemical fuels, but this process requires active and robust catalysts that can oxidize water to provide a source of electrons for proton reduction. Here we report the direct, covalent grafting of molecular Ir complexes onto carbon electrodes, with up to a monolayer coverage. Carbon-grafted Ir complexes electrochemically oxidize water with a turnover frequency of up to 3.3 s–1 and a turnover number of 644 during the first hour. Electrochemical water oxidation with grafted catalysts gave enhanced rates and stability compared to chemically driven water oxidation with the corresponding molecular catalysts. This strategy provides a way to systematically evaluate catalysts under tunable conditions, potentially providing new insights into electrochemical water oxidation processes and water oxidation catalyst design.Keywords: carbon electrode; diazonium grafting; electrocatalysis; water oxidation; water splitting;
Co-reporter:David J. Mihalcik ; Teng Zhang ; Liqing Ma
Inorganic Chemistry 2012 Volume 51(Issue 4) pp:2503-2508
Publication Date(Web):January 6, 2012
DOI:10.1021/ic2024296
A series of highly porous 4,8-connected isoreticular MOFs of the scu topology [Cu4(L1)(H2O)4]·20DEF, [Cu4(L2)(H2O)4]·16DMF·5H2O, and [Cu4(L3)(H2O)4]·14DMF (L1–L3 are (R)-1,1′-binaphthyl-derived octacarboxylate bridging ligands) were synthesized and characterized by single-crystal X-ray crystallography. Although the frameworks exhibit some distortion during the solvent removal process, the high-connectivity nature of the building blocks helps in stabilizing the frameworks, leading to high surface areas (SBET = 1189–2448 m2/g) and significant hydrogen uptake of up to 1.8 wt % (77 K, 1 atm).
Co-reporter:Aiguo Hu, Sophie Liu and Wenbin Lin
RSC Advances 2012 vol. 2(Issue 6) pp:2576-2580
Publication Date(Web):08 Feb 2012
DOI:10.1039/C2RA01073A
Magnetite nanoparticle (MNP)-supported asymmetric catalysts were synthesized by direct immobilization of a 4,4′-bisphosphonic acid-substituted BINAP-Ru-DPEN complex onto MNPs. The resulting heterogeneous catalyst (7) was highly active for the asymmetric hydrogenation of a wide range of aromatic ketones with remarkably high activity (>99% conversion with 0.1 mol% catalyst) and enantioselectivity (up to 98.1% ee) as a result of the bulky 4,4′-substituents (i.e., phosphonic acid groups) on BINAP. Catalyst 7 could be readily recycled and reused through simple magnetic decantation 9 times without the loss of activity or enantioselectivity. An alternative strategy was also explored to immobilize the [4,4′-(TMS)2-BINAP]-Ru-DPEN complex onto MNPs by first grafting a DPEN derivative onto the MNP surface followed by complexation of [4,4′-(TMS)2-BINAP]-Ru(DMF)2Cl2 to the surface-bound DPEN, but this immobilization strategy did not provide a robust heterogeneous catalyst, presumably due to oxidation of the Ru(II) intermediate by iron oxide nanoparticles.
Co-reporter:Joseph M. Falkowski;Sophie Liu
Israel Journal of Chemistry 2012 Volume 52( Issue 7) pp:591-603
Publication Date(Web):
DOI:10.1002/ijch.201100159
Abstract
This review documents the evolution of chiral MOF catalysts from simple Lewis acid and Lewis base catalysts that afford limited selectivity to more recent advancements that exhibit high stereo- and regioselectivities. MOF-based catalysts provide unprecedented opportunities for interrogating structure-activity relationships at high structural precision and for controlling catalytic activity by using external stimuli. The most notable disadvantage of MOF-based catalysts has been the inherent instability of the materials. This hurdle, which effectively limits the reaction scope of MOF catalysts, is slowly being overcome by the advent of new binding moieties and secondary building units.
Co-reporter:Joseph Della Rocca, Demin Liu, and Wenbin Lin
Accounts of Chemical Research 2011 Volume 44(Issue 10) pp:957
Publication Date(Web):June 7, 2011
DOI:10.1021/ar200028a
Metal–organic frameworks (MOFs), a class of hybrid materials formed by the self-assembly of polydentate bridging ligands and metal-connecting points, have been studied for a variety of applications. Recently, these materials have been scaled down to nanometer sizes, and this Account details the development of nanoscale metal–organic frameworks (NMOFs) for biomedical applications. NMOFs possess several potential advantages over conventional nanomedicines such as their structural and chemical diversity, their high loading capacity, and their intrinsic biodegradability. Under relatively mild conditions, NMOFs can be obtained as either crystalline or amorphous materials. The particle composition, size, and morphology can be easily tuned to optimize the final particle properties. Researchers have employed two general strategies to deliver active agents using NMOFs: by incorporating active agents into the frameworks or by loading active agents into the pores and channels of the NMOFs. The modification of NMOF surfaces with either silica coatings or organic polymers improves NMOF stability, fine-tunes their properties, and imparts additional functionality.Preliminary biomedical applications of NMOFs have focused on their use as delivery vehicles for imaging contrast agents and molecular therapeutics. Because NMOFs can carry large amounts of paramagnetic metal ions, they have been extensively explored as magnetic resonance imaging (MRI) contrast agents. Both Gd3+- and Mn2+-containing NMOFs have shown excellent efficacy as T1-weighted contrast agents with large per metal- and per particle-based MR relaxivities. Fe3+-containing NMOFs have demonstrated excellent T2-weighted contrast enhancement. Upon intravenous injection of iron carboxylate NMOFs in Wistar rats, researchers observed negative signal enhancement in the liver and spleen, which dissipated over time, indicating the degradation and clearance of the NMOF. Through the incorporation of luminescent or high Z element building blocks, NMOFs have also served as viable contrast agents for optical imaging or X-ray computed tomography (CT) imaging. Incorporation of membrane impermeable dyes into NMOFs allowed for their uptake by cancer cells and for their controlled release as the framework decomposed.NMOFs have been used to deliver anticancer drugs and other chemotherapeutics. Cisplatin prodrugs were incorporated within NMOFs at exceptionally high levels, either through use of the prodrug as the building block or through attachment of the prodrug onto the framework after synthesis. These NMOFs were encapsulated within a silica shell and targeted to cancer cells. In vitro assays revealed that the targeted NMOFs possessed similar efficacy to cisplatin, while the nontargeted NMOFs were less active. Several different therapeutic molecules were loaded within porous iron-carboxylate NMOFs at unprecedented levels. The NMOF showed sustained drug release with no burst effect, and in vitro assays revealed that the nanoencapsulated drug possessed similar efficacy to the free drug. Although still at a very early stage of development, NMOFs have already shown great promise as a novel platform for nanomedicine. The compositional tunability and mild synthetic conditions used to produce NMOFs should allow for the incorporation of other imaging and therapeutic agents and their effective delivery to targeted cells in vivo.
Co-reporter:Caleb A. Kent ; Demin Liu ; Liqing Ma ; John M. Papanikolas ; Thomas J. Meyer
Journal of the American Chemical Society 2011 Volume 133(Issue 33) pp:12940-12943
Publication Date(Web):July 21, 2011
DOI:10.1021/ja204214t
Microscale metal–organic frameworks (MOFs) were synthesized from photoactive Ru(II)-bpy building blocks with strong visible light absorption and long-lived triplet metal-to-ligand charge transfer (3MLCT) excited states. These MOFs underwent efficient luminescence quenching in the presence of either oxidative or reductive quenchers. Up to 98% emission quenching was achieved with either an oxidative quencher (1,4-benzoquinone) or a reductive quencher (N,N,N′,N′-tetramethylbenzidine), as a result of rapid energy migration over several hundred nanometers followed by efficient electron transfer quenching at the MOF/solution interface. The photoactive MOFs act as an excellent light-harvesting system by combining intraframework energy migration and interfacial electron transfer quenching.
Co-reporter:Cheng Wang ; Zhigang Xie ; Kathryn E. deKrafft
Journal of the American Chemical Society 2011 Volume 133(Issue 34) pp:13445-13454
Publication Date(Web):July 22, 2011
DOI:10.1021/ja203564w
Catalytically competent Ir, Re, and Ru complexes H2L1–H2L6 with dicarboxylic acid functionalities were incorporated into a highly stable and porous Zr6O4(OH)4(bpdc)6 (UiO-67, bpdc = para-biphenyldicarboxylic acid) framework using a mix-and-match synthetic strategy. The matching ligand lengths between bpdc and L1–L6 ligands allowed the construction of highly crystalline UiO-67 frameworks (metal–organic frameworks (MOFs) 1–6) that were doped with L1–L6 ligands. MOFs 1–6 were isostructural to the parent UiO-67 framework as shown by powder X-ray diffraction (PXRD) and exhibited high surface areas ranging from 1092 to 1497 m2/g. MOFs 1–6 were stable in air up to 400 °C and active catalysts in a range of reactions that are relevant to solar energy utilization. MOFs 1–3 containing [Cp*IrIII(dcppy)Cl] (H2L1), [Cp*IrIII(dcbpy)Cl]Cl (H2L2), and [IrIII(dcppy)2(H2O)2]OTf (H2L3) (where Cp* is pentamethylcyclopentadienyl, dcppy is 2-phenylpyridine-5,4′-dicarboxylic acid, and dcbpy is 2,2′-bipyridine-5,5′-dicarboxylic acid) were effective water oxidation catalysts (WOCs), with turnover frequencies (TOFs) of up to 4.8 h–1. The [ReI(CO)3(dcbpy)Cl] (H2L4) derivatized MOF 4 served as an active catalyst for photocatalytic CO2 reduction with a total turnover number (TON) of 10.9, three times higher than that of the homogeneous complex H2L4. MOFs 5 and 6 contained phosphorescent [IrIII(ppy)2(dcbpy)]Cl (H2L5) and [RuII(bpy)2(dcbpy)]Cl2 (H2L6) (where ppy is 2-phenylpyridine and bpy is 2,2′-bipyridine) and were used in three photocatalytic organic transformations (aza-Henry reaction, aerobic amine coupling, and aerobic oxidation of thioanisole) with very high activities. The inactivity of the parent UiO-67 framework and the reaction supernatants in catalytic water oxidation, CO2 reduction, and organic transformations indicate both the molecular origin and heterogeneous nature of these catalytic processes. The stability of the doped UiO-67 catalysts under catalytic conditions was also demonstrated by comparing PXRD patterns before and after catalysis. This work illustrates the potential of combining molecular catalysts and MOF structures in developing highly active heterogeneous catalysts for solar energy utilization.
Co-reporter:Cheng Wang
Journal of the American Chemical Society 2011 Volume 133(Issue 12) pp:4232-4235
Publication Date(Web):March 8, 2011
DOI:10.1021/ja111197d
Diffusion-controlled luminescence quenching of a phosphorescent metal−organic framework built from the Ru(bpy)32+-derived bridging ligand (MOF-1) was studied using a series of amines of different sizes as quenchers. The dynamics of amine diffusion into solvent-filled MOF-1 channels was probed by modeling time-dependent luminescence quenching data, which provide quantitative diffusion coefficients for the amine quenchers. Triethylamine, tripropylamine, and tributylamine were found to follow Fickian diffusion with a diffusivity of (1.1 ± 0.2) × 10−13, (4.8 ± 1.2) × 10−14, and (4.0 ± 0.4) × 10−14 m2/s, respectively. Diisopropylethylamine (DIPEA), on the other hand, was found to be too large to enter the MOF channels. Despite its size, 4-MeOPhNPh2 can enter the MOF channels via a slow, complicated framework/guest intercalation process to result in extensive framework distortion as revealed by powder X-ray diffraction. This work represents the first quantitative study of the dynamics of molecular diffusion into solvent-filled MOF channels. Such quantitative information on molecular diffusion in MOFs is of fundamental importance to many of their potential applications (e.g., heterogeneous catalysis).
Co-reporter:Liqing Ma, Marcela M. Wanderley, and Wenbin Lin
ACS Catalysis 2011 Volume 1(Issue 7) pp:691
Publication Date(Web):May 5, 2011
DOI:10.1021/cs2001303
A series of five chiral cross-linked polymers (CCPs) based on the 1,1′-binaphthyl building blocks have been synthesized via the trimerization reaction of terminal alkyne groups, catalyzed by octacarbonyldicobalt complex (Co2(CO)8). The CCPs were highly porous, with surface areas of 689 to 974 m2/g and pore volumes of 0.87 to 1.23 cm3/g. The CCPs were insoluble in all solvents tested, including concentrated hydrochloric acid. The CCPs containing chiral dihydroxy functionalities were treated with Ti(OiPr)4 to generate chiral Lewis acid catalysts for the asymmetric diethylzinc addition to aldehydes. The enantioselectivity of these reactions is modest to good (55 to 81 e.e.%), but the CCPs could be readily recycled and reused for the asymmetric diethylzinc addition reactions for up to 10 times without loss of conversion or enantioselectivity.Keywords: asymmetric catalysis; chirality; crosslinked polymers; heterogeneous catalysis; porous materials
Co-reporter:Feijie Song, Cheng Wang and Wenbin Lin
Chemical Communications 2011 vol. 47(Issue 29) pp:8256-8258
Publication Date(Web):22 Jun 2011
DOI:10.1039/C1CC12701B
A chiral metal–organic framework (MOF) of the lcy topology was constructed from the Mn–Salen derived dicarboxylic acid and the [Zn4(μ4-O)(O2CR)6] secondary building unit, and used in highly regio- and stereo-selective sequential alkene epoxidation/epoxide ring-opening reactions.
Co-reporter:Joseph M. Falkowski;Cheng Wang;Sophie Liu ; Wenbin Lin
Angewandte Chemie International Edition 2011 Volume 50( Issue 37) pp:8674-8678
Publication Date(Web):
DOI:10.1002/anie.201104086
Co-reporter:Joseph M. Falkowski;Cheng Wang;Sophie Liu ; Wenbin Lin
Angewandte Chemie 2011 Volume 123( Issue 37) pp:8833-8837
Publication Date(Web):
DOI:10.1002/ange.201104086
Co-reporter:Demin Liu;Rachel C. Huxford ; Wenbin Lin
Angewandte Chemie 2011 Volume 123( Issue 16) pp:3780-3784
Publication Date(Web):
DOI:10.1002/ange.201008277
Co-reporter:Cheng Wang, Min Zheng, and Wenbin Lin
The Journal of Physical Chemistry Letters 2011 Volume 2(Issue 14) pp:1701-1709
Publication Date(Web):June 29, 2011
DOI:10.1021/jz200492d
Chiral metal–organic frameworks (MOFs) have shown great promise as highly efficient and recyclable heterogeneous catalysts in asymmetric reactions. Following a brief introduction of basic concepts and potential virtues of MOFs in catalysis, five critical issues pertinent to the fundamental understanding of MOF asymmetric catalysis are discussed: strategies to construct and sustain reagent-accessible channels, framework distortion and characterization of large open channels in MOFs, substrate diffusion through the MOF channels, the dependence of catalytic activities and stereoselectivities on MOF open channel sizes, and detailed elucidation of structure–property relationships via single-crystal-to-single-crystal transformations. A perspective on further development of chiral MOF catalysts in the potential production of optically pure organic molecules is also given.
Co-reporter:Demin Liu;Rachel C. Huxford ; Wenbin Lin
Angewandte Chemie International Edition 2011 Volume 50( Issue 16) pp:3696-3700
Publication Date(Web):
DOI:10.1002/anie.201008277
Co-reporter:Joseph DellaRocca;Rachel C. Huxford;Erica Comstock-Duggan ; Wenbin Lin
Angewandte Chemie International Edition 2011 Volume 50( Issue 44) pp:10330-10334
Publication Date(Web):
DOI:10.1002/anie.201104510
Co-reporter:Joseph DellaRocca;Rachel C. Huxford;Erica Comstock-Duggan ; Wenbin Lin
Angewandte Chemie 2011 Volume 123( Issue 44) pp:10514-10518
Publication Date(Web):
DOI:10.1002/ange.201104510
Co-reporter:Feijie Song ; Cheng Wang ; Joseph M. Falkowski ; Liqing Ma
Journal of the American Chemical Society 2010 Volume 132(Issue 43) pp:15390-15398
Publication Date(Web):October 11, 2010
DOI:10.1021/ja1069773
A family of isoreticular chiral metal−organic frameworks (CMOFs) of the primitive cubic network topology was constructed from [Zn4(μ4-O)(O2CR)6] secondary building units and systematically elongated dicarboxylate struts that are derived from chiral Mn-Salen catalytic subunits. CMOFs 1−5 were synthesized by directly incorporating three different chiral Mn-Salen struts into the frameworks under solvothermal conditions, and they were characterized by a variety of methods, including single-crystal X-ray diffraction, PXRD, TGA, and 1H NMR. Although the CMOFs 1 vs 2 and CMOFs 3 vs 4 pairs were constructed from the same building blocks, they exhibit two-fold interpenetrated or non-interpenetrated structures, respectively, depending on the steric sizes of the solvents that were used to grow the MOF crystals. For CMOF-5, only a three-fold interpenetrated structure was obtained due to the extreme length of the Mn-Salen-derived dicarboxylate strut. The open channel and pore sizes of the CMOF series vary systematically, owing to the tunable dicarboxylate struts and controllable interpenetration patterns. CMOFs 1−5 were shown to be highly effective catalysts for asymmetric epoxidation of a variety of unfunctionalized olefins with up to 92% ee. The rates of epoxidation reactions strongly depend on the CMOF open channel sizes, and the catalytic activities of CMOFs 2 and 4 approach that of a homogeneous control catalyst. These results suggest that, although the diffusion of bulky alkene and oxidant reagents can be a rate-limiting factor in MOF-catalyzed asymmetric reactions, the catalytic activity of the CMOFs with large open channels (such as CMOFs 2 and 4 in the present study) is limited by the intrinsic reactivity of the catalytic molecular building blocks. The CMOF catalysts are recyclable and reusable and retain their framework structures after epoxidation reactions. This work highlights the potential of generating highly effective heterogeneous asymmetric catalysts via direct incorporation of well-defined homogeneous catalysts into framework structures of MOFs.
Co-reporter:Caleb A. Kent ; Brian P. Mehl ; Liqing Ma ; John M. Papanikolas ; Thomas J. Meyer
Journal of the American Chemical Society 2010 Volume 132(Issue 37) pp:12767-12769
Publication Date(Web):August 25, 2010
DOI:10.1021/ja102804s
Isomorphous metal−organic frameworks (MOFs) based on {M[4,4′-(HO2C)2-bpy]2bpy}2+ building blocks (where M = Ru or Os) were designed and synthesized to study the classic Ru to Os energy transfer process that has potential applications in light-harvesting with supramolecular assemblies. The crystalline nature of the MOFs allows precise determination of the distances between metal centers by X-ray diffraction, thereby facilitating the study of the Ru→Os energy transfer process. The mixed-metal MOFs with 0.3, 0.6, 1.4, and 2.6 mol % Os doping were also synthesized in order to study the energy transfer dynamics with a two-photon excitation at 850 nm. The Ru lifetime at 620 nm decreases from 171 ns in the pure Ru MOF to 29 ns in the sample with 2.6 mol % Os doping. In the mixed-metal samples, energy transfer was observed with an initial growth in Os emission corresponding with the rate of decay of the Ru excited state. These results demonstrate rapid, efficient energy migration and long distance transfer in isomorphous MOFs.
Co-reporter:Demin Liu ; Zhigang Xie ; Liqing Ma
Inorganic Chemistry 2010 Volume 49(Issue 20) pp:9107-9109
Publication Date(Web):September 22, 2010
DOI:10.1021/ic1009169
Two three-dimensional metal−organic frameworks (MOFs) with tetraphenylmethane-derived tetracarboxylate linkers and copper paddle-wheel secondary building units were synthesized and characterized by single-crystal X-ray crystallographic studies. The two MOFs show a similar 4,4-connectivity but very different homocrossing and interpenetrating PtS network topologies and exhibit permanent porosity as probed by gas adsorption and dye inclusion experiments.
Co-reporter:Joseph Della Rocca
European Journal of Inorganic Chemistry 2010 Volume 2010( Issue 24) pp:3725-3734
Publication Date(Web):
DOI:10.1002/ejic.201000496
Abstract
Magnetic resonance imaging (MRI) is an imaging technique based on the detection of nuclear spin reorientations in a magnetic field. MRI provides high spatial resolution and soft-tissue contrast in anatomical images, and a large penetration depth; however, it is relatively insensitive and typically relies on large doses of administered contrast agents to give adequate contrast between normal and diseased tissues. This review covers the development of nanoscale metal–organic frameworks (NMOFs) as novel MRI contrast agents. NMOFs not only provide an effective vehicle for delivering large amounts of paramagnetic metal centers but also exhibit enhanced per-metal-based relaxivity relative to clinically used small-molecule contrast agents. The in vitro and in vivo effectiveness of these agents has also been demonstrated. The potential of NMOFs as contrast agents for other imaging modalities, such as optical imaging (OI) and X-ray computed tomography (CT), and as chemical and biological sensors is also discussed.
Co-reporter:Wenbin Lin;Rol A. Fischer;J.-S. Chen;Dirk E. De Vos
European Journal of Inorganic Chemistry 2010 Volume 2010( Issue 24) pp:
Publication Date(Web):
DOI:10.1002/ejic.201090069
Abstract
The cover picture a schematic design of a porous metal–organic framework as the background. Embedded in the MOF are illustrations representing some of the thought-provoking contributions that make up this Cluster Issue entitled “Targeted Fabrication of MOFs for Hybrid Functionality”. With a focus towards application, this issue serves to showcase the research at the forefront of the field. The top left-hand graphic symbolises the use of nanoscale MOFs as MRI contrast agents (W. Lin et al.; p. 3725 ff), while the bottom left depicts the use of MOFs as supports for metal nanoparticles in catalysis (R. A. Fischer et al.; p. 3701 ff). The structure–property relationship of uranyl–organic frameworks (top right-hand corner), important in photovoltaics is highlighted by J.-S. Chen et al. (p. 3780 ff), and the synthesis of MOF composites for use as a stationary phase in HPLC (bottom right-hand corner) is discussed by D. E. De Vos et al. (p. 3735 ff). A sincere thanks to the authors for their excellent contributions to the cover. We thank Heulwen Price for designing the background.
Co-reporter:Dr. Liqing Ma;Dr. Chuan-De Wu;Marcela M. Werley ; Wenbin Lin
Angewandte Chemie 2010 Volume 122( Issue 44) pp:8420-8424
Publication Date(Web):
DOI:10.1002/ange.201003377
Co-reporter:Dr. Liqing Ma;Dr. Chuan-De Wu;Marcela M. Werley ; Wenbin Lin
Angewandte Chemie International Edition 2010 Volume 49( Issue 44) pp:8244-8248
Publication Date(Web):
DOI:10.1002/anie.201003377
Co-reporter:Wenbin Lin
Topics in Catalysis 2010 Volume 53( Issue 13-14) pp:869-875
Publication Date(Web):2010 August
DOI:10.1007/s11244-010-9519-3
This paper provides a brief overview of recent progress in the design and synthesis of chiral metal–organic frameworks (CMOFs) and their applications in heterogeneous asymmetric catalysis. Catalytically active CMOFs can be synthesized using two distinct strategies, either by post-synthetic activation of pre-synthesized porous MOFs or by directly linking well-designed catalytically competent bridging ligands with metal ion or metal cluster nodes. Heterogeneous asymmetric catalysis with very high activity and enantioselectivity has been achieved with CMOFs. The intrinsic tunability of CMOFs promises to lead to the design and synthesis of a variety of practically useful heterogeneous asymmetric catalysts for many organic transformations.
Co-reporter:Helen L. Ngo;Nicholas A. Zafiropoulos
Journal of the American Oil Chemists' Society 2010 Volume 87( Issue 4) pp:445-452
Publication Date(Web):2010 April
DOI:10.1007/s11746-009-1509-x
Biodiesel (BD), typically consisting of fatty acid methyl esters (FAME), has received much attention because it is a renewable biofuel that contributes little to global warming compared to petroleum-based diesel fuel. The most common method used for BD production is based on the alkali-catalyzed transesterification of first-use refined oils and fats with an alcohol (e.g. methanol). These technologies, however, require significant modification when applied to second use materials such as greases because of their higher free fatty acid (FFA) content. Recently, we reported a series of insoluble porous polymer grafted diphenylammonium salts that efficiently esterified the FFA in greases to FAME. In this work, the diphenylammonium salts were supported onto two robust mesoporous silicas. The resulting catalysts had high esterification activity with >99% of the FFA in greases converted to FAME, and the FFA content in the treated greases was reduced to <1 wt%. The mesoporous silica-supported catalysts displayed minimal transesterification activity.
Co-reporter:Liqing Ma, Carter Abney and Wenbin Lin
Chemical Society Reviews 2009 vol. 38(Issue 5) pp:1248-1256
Publication Date(Web):23 Feb 2009
DOI:10.1039/B807083K
This tutorial review presents recent developments of homochiral metal–organic frameworks (MOFs) in enantioselective catalysis. Following a brief introduction of the basic concepts and potential virtues of MOFs in catalysis, we summarize three distinct strategies that have been utilized to synthesize homochiral MOFs. Framework stability and accessibility of the open channels to reagents are then addressed. We finally survey recent successful examples of catalytically active homochiral MOFs based on three approaches, namely, homochiral MOFs with achiral catalytic sites, incorporation of asymmetric catalysts directly into the framework, and post-synthetic modification of homochiral MOFs. Although still in their infancy, homochiral MOFs have clearly demonstrated their utility in heterogeneous asymmetric catalysis, and a bright future is foreseen for the development of practically useful homochiral MOFs in the production of optically pure organic molecules.
Co-reporter:Kathryn M. L. Taylor-Pashow ; Joseph Della Rocca ; Zhigang Xie ; Sylvie Tran
Journal of the American Chemical Society 2009 Volume 131(Issue 40) pp:14261-14263
Publication Date(Web):September 16, 2009
DOI:10.1021/ja906198y
Fe(III)-carboxylate nanoscale metal−organic frameworks (NMOFs) with the MIL-101 structure were synthesized using a solvothermal technique with microwave heating. The ∼200 nm particles were characterized using a variety of methods, including SEM, PXRD, nitrogen adsorption measurements, TGA, and EDX. By replacing a percentage of the bridging ligand (terephthalic acid) with 2-amino terephthalic acid, amine groups were incorporated into the framework to provide sites for covalent attachment of biologically relevant cargoes while still maintaining the MIL-101 structure. In proof-of-concept experiments, an optical contrast agent (a BODIPY dye) and an ethoxysuccinato-cisplatin anticancer prodrug were successfully incorporated into the Fe(III)-carboxylate NMOFs via postsynthetic modifications of the as-synthesized particles. These cargoes are released upon the degradation of the NMOF frameworks, and the rate of cargo release was controlled by coating the NMOF particles with a silica shell. Potential utility of the new NMOF-based nanodelivery vehicles for optical imaging and anticancer therapy was demonstrated in vitro using HT-29 human colon adenocarcinoma cells.
Co-reporter:Kathryn M. L. Taylor and Wenbin Lin
Journal of Materials Chemistry A 2009 vol. 19(Issue 35) pp:6418-6422
Publication Date(Web):18 May 2009
DOI:10.1039/B900866G
Lanthanide luminescence is a common method for the detection of dipicolinic acid (DPA), a chemical marker for bacterial spores. In this paper we report the development of silica nanoparticle based luminescent sensors for DPA detection. The sensors consist of three different modified EDTA–Tb complexes immobilized on 37 nm solid silica nanoparticles. The use of a nanoparticle platform also allows for the incorporation of an internal reference which eliminates the need for instrument-specific calibration curves for DPA quantification in an analyte. Limits of detection on the order of nanomolar concentrations can be achieved using these nanoparticle based DPA luminescence sensors.
Co-reporter:Shuting Wu, Liqing Ma, La-Sheng Long, Lan-Sun Zheng and Wenbin Lin
Inorganic Chemistry 2009 Volume 48(Issue 6) pp:2436-2442
Publication Date(Web):February 18, 2009
DOI:10.1021/ic801631w
New tetracarboxylate ligands with dihydroxy (L1) and crown ether functionalities (L2) have been synthesized and treated with CuII and ZnII ions to generate three-dimensional (3D) metal-organic frameworks (MOFs) with the compositions of [Cu2(L1)(H2O)2]·14DMF·10H2O, 5, [Cu2(L2)(H2O)2]·12DMF, 6, [Zn6(μ4-O)(L1)2(L1-H2)]·35DMF·27H2O, 7, and [Zn3Na2(L2)2(DMF)2]·7DMF·14H2O, 8. The four compounds show different framework structures with different connectivities. Compound 5 exhibits the PtS topology whereas compound 6 has a [64.82]3[66] topology. Compound 7 adopts a new [4.65][42.68][44.62][45.6][48.610.83] topology while compound 8 exhibits the Flu topology. The porosity and H2 uptake were studied by gas sorption experiments and grand canonical Monte Carlo (GCMC) simulations. Compound 5 shows a high H2 uptake of up to 1.11 wt % at 77 K.
Co-reporter:DavidJ. Mihalcik Dr.
ChemCatChem 2009 Volume 1( Issue 3) pp:406-413
Publication Date(Web):
DOI:10.1002/cctc.200900188
Abstract
Chiral RuCl2–diphosphine–diamine complexes with a pendant siloxy group were synthesized and characterized by NMR spectroscopy and mass spectrometry. The Ru complexes were grafted onto three different types of mesoporous silica nanospheres (MSNs) through the siloxane linkage, and the resulting MSN-supported Ru catalysts were highly active for the asymmetric hydrogenation of aromatic ketones, to afford chiral secondary alcohols, and racemic arylaldehydes, to give chiral primary alcohols. Excellent activities and enantioselectivities were observed for these MSN-supported Ru catalysts owing to readily accessible and uniform catalytic sites within the large channels of MSNs (diameters of >2 nm) and short diffusion lengths for the organic compounds as a result of small nanoparticle sizes of less than 1 μm. This catalyst immobilization strategy with MSN supports should be amenable to the design of many highly active and enantioselective heterogeneous asymmetric catalysts.
Co-reporter:Liqing Ma Dr.
Angewandte Chemie 2009 Volume 121( Issue 20) pp:3691-3694
Publication Date(Web):
DOI:10.1002/ange.200806227
Co-reporter:KathrynE. deKrafft;Zhigang Xie Dr.;Guohua Cao Dr.;Sylvie Tran;Liqing Ma Dr.;OttoZ. Zhou
Angewandte Chemie 2009 Volume 121( Issue 52) pp:10085-10088
Publication Date(Web):
DOI:10.1002/ange.200904958
Co-reporter:Liqing Ma Dr.;Athena Jin;Zhigang Xie Dr.
Angewandte Chemie 2009 Volume 121( Issue 52) pp:10089-10092
Publication Date(Web):
DOI:10.1002/ange.200904983
Co-reporter:Wenbin Lin Dr.;WilliamJ. Rieter Dr. ;KathrynM.L. Taylor
Angewandte Chemie 2009 Volume 121( Issue 4) pp:660-668
Publication Date(Web):
DOI:10.1002/ange.200803387
Abstract
Die koordinativ vermittelte Organisation von Metallionen und organischen Brückenliganden liefert Hybridmaterialien mit vielversprechenden Eigenschaften für Anwendungen etwa in der Gasspeicherung und heterogenen Katalyse. Eine besondere Klasse von Hybridmaterialien sind die Koordinationspolymere. In diesem Kurzaufsatz betrachten wir jüngste Entwicklungen bei der Synthese von amorphen und kristallinen nanoskaligen Koordinationspolymeren und zeigen, dass die Maßstabsverkleinerung in den Nanometerbereich zu breiten Anwendungsmöglichkeiten führt, z. B. in der Katalyse, für Spin-Crossover-Materialien, zur Verwendung als Templat, in der Biosensorik, der biomedizinischen Bildgebung und im Wirkstofftransport. Die Ergebnisse unterstreichen das Potenzial funktioneller Nanomaterialien aus molekularen Komponenten.
Co-reporter:KathrynE. deKrafft;Zhigang Xie Dr.;Guohua Cao Dr.;Sylvie Tran;Liqing Ma Dr.;OttoZ. Zhou
Angewandte Chemie International Edition 2009 Volume 48( Issue 52) pp:9901-9904
Publication Date(Web):
DOI:10.1002/anie.200904958
Co-reporter:Liqing Ma Dr.;Athena Jin;Zhigang Xie Dr.
Angewandte Chemie International Edition 2009 Volume 48( Issue 52) pp:9905-9908
Publication Date(Web):
DOI:10.1002/anie.200904983
Co-reporter:Liqing Ma Dr.
Angewandte Chemie International Edition 2009 Volume 48( Issue 20) pp:3637-3640
Publication Date(Web):
DOI:10.1002/anie.200806227
Co-reporter:Wenbin Lin Dr.;WilliamJ. Rieter Dr. ;KathrynM.L. Taylor
Angewandte Chemie International Edition 2009 Volume 48( Issue 4) pp:650-658
Publication Date(Web):
DOI:10.1002/anie.200803387
Abstract
The coordination-directed assembly of metal ions and organic bridging ligands has afforded a variety of bulk-scale hybrid materials with promising characteristics for a number of practical applications, such as gas storage and heterogeneous catalysis. Recently, so-called coordination polymers have emerged as a new class of hybrid nanomaterials. Herein, we highlight advances in the syntheses of both amorphous and crystalline nanoscale coordination polymers. We also illustrate how scaling down these materials to the nano-regime has enabled their use in a broad range of applications including catalysis, spin-crossover, templating, biosensing, biomedical imaging, and anticancer drug delivery. These results underscore the exciting opportunities of developing next-generation functional nanomaterials based on molecular components.
Co-reporter:Liqing Ma, Jeong Yong Lee, Jing Li and Wenbin Lin
Inorganic Chemistry 2008 Volume 47(Issue 10) pp:3955-3957
Publication Date(Web):April 17, 2008
DOI:10.1021/ic8003855
Two 3D metal−organic frameworks (MOFs) with a new biphenol-derived tetracarboxylate linker and CuII and ZnII metal-connecting points were synthesized and characterized by single-crystal X-ray crystallographic studies. The two isostructural MOFs exhibit distorted PtS network topology and show markedly different framework stability. The porosity and hydrogen uptake of the frameworks were determined by gas adsorption experiments.
Co-reporter:Chuan-De Wu, Liqing Ma and Wenbin Lin
Inorganic Chemistry 2008 Volume 47(Issue 24) pp:11446-11448
Publication Date(Web):November 11, 2008
DOI:10.1021/ic800514f
Hierarchically ordered homochiral metal−organic frameworks were built from the CuII connecting point and the new (R)-6,6′-dichloro-2,2′-diethoxy-1,1′-binaphthyl-4,4′-bis(p-ethynylpyridine) bridging ligand (L). [Cu3L4(DMF)6(H2O)3(ClO4)][ClO4]5·10DMF·10EtOH·7H2O (1) adopts a unique three-dimensional framework structure via simultaneous interlocking and interpenetration of one-dimensional ladders formed by linking rectangles of 24.8 × 48.6 Å2 in dimensions, whereas [Cu3L5(DMF)8][ClO4]6·6DMF·8EtOH·Et2O·6H2O (2) exhibits an interesting network topology by threading two-dimensional coordination square grids with one-dimensional coordination polymers.
Co-reporter:KathrynM.L. Taylor;Athena Jin
Angewandte Chemie 2008 Volume 120( Issue 40) pp:7836-7839
Publication Date(Web):
DOI:10.1002/ange.200802911
Co-reporter:DavidJ. Mihalcik
Angewandte Chemie International Edition 2008 Volume 47( Issue 33) pp:6229-6232
Publication Date(Web):
DOI:10.1002/anie.200705656
Co-reporter:KathrynM.L. Taylor;Athena Jin
Angewandte Chemie International Edition 2008 Volume 47( Issue 40) pp:7722-7725
Publication Date(Web):
DOI:10.1002/anie.200802911
Co-reporter:DavidJ. Mihalcik
Angewandte Chemie 2008 Volume 120( Issue 33) pp:6325-6328
Publication Date(Web):
DOI:10.1002/ange.200705656
Co-reporter:Nicholas A. Zafiropoulos, Helen L. Ngo, Thomas A. Foglia, Edward T. Samulski and Wenbin Lin
Chemical Communications 2007 (Issue 35) pp:3670-3672
Publication Date(Web):27 Jun 2007
DOI:10.1039/B704189F
Recyclable and reusable heterogeneous diarylammonium catalysts are highly effective in catalyzing the esterification of the free fatty acid (FFA) present in greases to methyl esters to reduce the FFA content from 12–40 wt% to 0.5–1 wt%; the resulting ester–glyceride mixture (pretreated grease) could then be readily converted to methyl esters by base-catalyzed transesterification.
Co-reporter:Chuan-De Wu Dr.
Angewandte Chemie International Edition 2007 Volume 46(Issue 7) pp:
Publication Date(Web):20 DEC 2006
DOI:10.1002/anie.200602099
It's all in the preparation: Heterogeneous asymmetric catalysts based on two homochiral highly porous metal–organic frameworks formed from the same building blocks show remarkably different activity. Although both catalysts are based on twofold interpenetrated structures, one catalyzes the addition of diethylzinc to aromatic aldehydes with high enantioselectivity (up to 90 % ee), while the other is inactive.
Co-reporter:William J. Rieter;Jason S. Kim;Kathryn M. L. Taylor;Hongyu An Dr.;Weili Lin ;Teresa Tarrant
Angewandte Chemie International Edition 2007 Volume 46(Issue 20) pp:
Publication Date(Web):5 APR 2007
DOI:10.1002/anie.200604738
Lighting things up: Multifunctional silica nanoparticles containing a luminescent core and a paramagnetic coat are prepared, and their utility as multimodal imaging probes is demonstrated in vitro. Monocyte cells can be labeled with the hybrid nanoparticles with greater than 98 % efficiency and do not experience measurable toxicity even at a high loading of 0.123 mg per 5000 cells.
Co-reporter:Chuan-De Wu Dr.
Angewandte Chemie 2007 Volume 119(Issue 7) pp:
Publication Date(Web):20 DEC 2006
DOI:10.1002/ange.200602099
Die Vorbereitung ist entscheidend: Heterogene asymmetrische Katalysatoren, die auf zwei homochiralen, hochporösen metall-organischen Gerüsten aus denselben Bausteinen beruhen, unterscheiden sich deutlich in ihrer Aktivität. Obwohl beide doppelte Durchdringungsstrukturen enthalten, katalysiert der eine die Addition von Diethylzink an aromatische Aldehyde mit hoher Enantioselektivität (bis 90 % ee), während der andere inaktiv ist.
Co-reporter:William J. Rieter;Jason S. Kim;Kathryn M. L. Taylor;Hongyu An Dr.;Weili Lin ;Teresa Tarrant
Angewandte Chemie 2007 Volume 119(Issue 20) pp:
Publication Date(Web):5 APR 2007
DOI:10.1002/ange.200604738
Erhellt: Siliciumoxid-Nanopartikel mit einem lumineszierenden Kern und einer paramagnetischen Hülle wurden hergestellt, und ihre Nützlichkeit als multimodale Imaging-Sonden wurde in vitro nachgewiesen. Monozyten wurden mit den hybriden Nanopartikeln mit einer Effizienz von über 98 % markiert, ohne dass selbst bei einer hohen Beladung von 0.123 mg pro 5000 Zellen eine messbare Toxizität auftrat.
Co-reporter:Aiguo Hu;Masamichi Ogasawara;Takeshi Sakamoto;Atsushi Okada;Kiyohiko Nakajima;Tamotsu Takahashi
Advanced Synthesis & Catalysis 2006 Volume 348(Issue 15) pp:
Publication Date(Web):12 OCT 2006
DOI:10.1002/adsc.200606208
A family of tunable precatalysts [Pd((S)-L*)(NCMe)2](OTf)2, where L* is 4,4′-disubstituted BINAP or SEGPHOS, was synthesized and used for the asymmetric intermolecular hydroamination of aniline to vinylarenes with ee values of up to 85 %, and it is believed that the bulky groups on the 4,4′-positions and the narrower dihedral angle of the biaryl moiety are responsible for the ee enhancement in these reactions.
Co-reporter:Lin Zhang, Yu-Hua Niu, Alex K.-Y. Jen and Wenbin Lin
Chemical Communications 2005 (Issue 8) pp:1002-1004
Publication Date(Web):11 Jan 2005
DOI:10.1039/B413708F
Chiral molecular triangles and squares containing the Pt(diimine) metallocorners were synthesized and characterized, and used as the triplet MLCT luminophore in highly efficient light-emitting devices.
Co-reporter:Chuan-De Wu and Wenbin Lin
Chemical Communications 2005 (Issue 29) pp:3673-3675
Publication Date(Web):15 Jun 2005
DOI:10.1039/B505916J
A novel homochiral 3D metal–organic framework [CdL2(H2O)2][ClO4]2·2DMF·3EtOH·5/3H2O, 1, (L =
(R)-6,6′-dichloro-2,2′-diethoxy-1,1′-binaphthyl-4,4′-bipyridine) exhibits an unprecedented 4-connected network topology owing to the cis- configuration of the Cd coordination and possesses permanent porosity as demonstrated by TGA, XRPD, and CO2 adsorption isotherm studies.
Co-reporter:Hua Jiang, Wenbin Lin
Journal of Organometallic Chemistry 2005 Volume 690(Issue 23) pp:5159-5169
Publication Date(Web):15 November 2005
DOI:10.1016/j.jorganchem.2005.03.049
Treatment of 2,2′-diacetoxy-1,1′-binaphthyl-6,6′-bis(ethyne), L-H2, with one equiv of trans-Pt(PEt3)2Cl2 led to a mixture of different sizes of chiral metallocycles [trans-(PEt3)2Pt(L)]n (n = 3–8, 1–6). Each of the chiral molecular polygons 1–6 was purified by silica-gel column chromatography and characterized by 1H, 13C{1H}, and 31P{1H} NMR spectroscopy, MS, IR, UV–Vis, and circular dichroism (CD) spectroscopies, size exclusion chromatography, and microanalysis. Chiral molecular square 2 was also characterized by single-crystal X-ray diffraction. The acetyl groups of 2 were readily deprotected under mild conditions to generate 2a which possesses exposed chiral dihydroxy functional groups. The dihydroxy groups were functionalized with n-octadecyl chains or Fréchet-type dendrons to generate dendritic molecules built on a chiral molecular square core. This work shows the potential of generating interesting functional supramolecular systems based on Pt-alkynyl chiral molecular polygons.Treatment of 2,2′-diacetoxy-1,1′-binaphthyl-6,6′-bis(ethyne) with one equiv of trans-Pt(PEt3)2Cl2 led to a mixture of different sizes of chiral metallocycles [trans-(PEt3)2Pt(L)]n (n = 3–8, 1–6). The acetyl groups of 2 were readily deprotected under mild conditions to generate 2a which possesses exposed chiral dihydroxy functional groups. The dihydroxy groups were functionalized with n-octadecyl chains or Fréchet-type dendrons to generate dendritic molecules built on a chiral molecular square core.
Co-reporter:Wenbin Lin
Journal of Solid State Chemistry 2005 Volume 178(Issue 8) pp:2486-2490
Publication Date(Web):August 2005
DOI:10.1016/j.jssc.2005.06.013
This paper highlights the most significant recent advances in the synthesis, characterization, and applications of single-crystalline homochiral porous metal-organic frameworks (MOFs). The motivations for the synthesis of homochiral porous solids and the strategies on how they can be designed are provided. The latest examples of chiral separation and Lewis acid heterogeneous asymmetric catalysis using homochiral porous MOFs are presented.A schematic representation of the active (BINOLate)Ti(OiPr)2 catalytic sites inside the open channels of a homochiral porous MOF.
Co-reporter:Banu Kesanli Dr.;Yong Cui Dr.;Milton R. Smith Dr.;Edward W. Bittner Dr.;Bradley C. Bockrath Dr.
Angewandte Chemie International Edition 2005 Volume 44(Issue 1) pp:
Publication Date(Web):15 DEC 2004
DOI:10.1002/anie.200461214
Packing them in: Based on zinc and aromatic-rich dicarboxylic acids these new coordination networks (see structure; green Cl, red O, yellow Zn, blue N, gray C) have hydrogen uptakes comparable to those of the best carbon nanotubes and metal–organic frameworks. The highly interpenetrating nature of these networks points to a new design strategy for hydrogen-storage materials that employ an entrapment mechanism.
Co-reporter:Banu Kesanli Dr.;Yong Cui Dr.;Milton R. Smith Dr.;Edward W. Bittner Dr.;Bradley C. Bockrath Dr.
Angewandte Chemie 2005 Volume 117(Issue 1) pp:
Publication Date(Web):15 DEC 2004
DOI:10.1002/ange.200461214
Eingepackt: Die hier vorgestellten Koordinationsnetzwerke auf der Basis von Zink und Aren-reichen Dicarbonsäuren (siehe Struktur; grau C, rot O, blau N, grün Cl, gelb Zn) ähneln in ihrer Wasserstoffaufnahme den besten Kohlenstoffnanoröhren und metall-organischen Gerüsten. Ihre ausgeprägten Durchdringungsstrukturen könnten Anregung für eine neue Strategie für das Design von Wasserstoffspeichermaterialien sein, die einen Fallenmechanismus nutzen.
Co-reporter:Chuan-De Wu Dr.
Angewandte Chemie 2005 Volume 117(Issue 13) pp:
Publication Date(Web):23 FEB 2005
DOI:10.1002/ange.200462711
Steter Wechsel: Hoch poröse homochirale metallo-organische Netzwerke (metal–organic frameworks, MOFs) zeigen reversible Kristall-zu-Kristall- und Kristallin-amorph-kristallin-Strukturumwandlungen, wenn sie Lösungsmitteldämpfen oder Luft ausgesetzt werden. Diesen Ergebnissen zufolge könnten ausgehend von homochiralen MOFs echte asymmetrische Heterogenkatalysatoren entwickelt werden.
Co-reporter:Chuan-De Wu Dr.
Angewandte Chemie International Edition 2005 Volume 44(Issue 13) pp:
Publication Date(Web):23 FEB 2005
DOI:10.1002/anie.200462711
Change and change about: Highly porous, homochiral metal–organic frameworks (MOFs) undergo reversible single-crystal to single-crystal and single-crystal to amorphous to single-crystal structural transformations when exposed to solvent vapors or air. These results suggest that true heterogeneous asymmetric catalysts can be built from homochiral MOFs.
Co-reporter:Banu Kesanli and Wenbin Lin
Chemical Communications 2004 (Issue 20) pp:2284-2285
Publication Date(Web):25 Aug 2004
DOI:10.1039/B406697A
Recyclable and reusable mesoporous silica anchored Ru catalysts based on 4,4′-substituted BINAPs were synthesized and used for the hydrogenation of β-alkyl β-ketoesters with up to 98.6% e.e. and β-aryl β-ketoesters with up to 95.2% e.e.
Co-reporter:Chuan-De Wu, Helen L. Ngo and Wenbin Lin
Chemical Communications 2004 (Issue 14) pp:1588-1589
Publication Date(Web):04 Jun 2004
DOI:10.1039/B403609C
The reactions of 2,2′-dimethoxy-1,1′-binaphthyl-3,3′-bis(4-vinylpyridine)
(L) with AgNO3 or AgClO4 at 70 °C gave rise to two novel luminescent homochiral lamellar coordination polymers, AgL2X (X = NO3− for 1 or ClO4− for 2), which are built from linking helical chains by Ag(I) atoms as hinges.
Co-reporter:Aiguo Hu Dr.;Helen L. Ngo
Angewandte Chemie 2004 Volume 116(Issue 19) pp:
Publication Date(Web):28 APR 2004
DOI:10.1002/ange.200353415
Chirale Diphosphane mit einstellbaren elektronischen und sterischen Eigenschaften sind geeignete Liganden in der asymmetrischen Hydrierung von β-Arylketoestern (bis zu 99.8 % ee). Die ausgezeichnete Performance dieser binap-Derivate beruht auf bemerkenswerten 4,4′-Substituenteneffekten. Die hoch enantioselektiven Ru-Katalysatoren konnten in ionischen Raumtemperaturflüssigkeiten (RTILs) immobilisiert werden.
Co-reporter:Helen L. Ngo, Aiguo Hu, Wenbin Lin
Journal of Molecular Catalysis A: Chemical 2004 Volume 215(1–2) pp:177-186
Publication Date(Web):14 June 2004
DOI:10.1016/j.molcata.2004.01.022
Porous zirconium phosphonates containing chiral dihydroxy functionalities have been synthesized via a building block approach. Enantiopure atropisomeric bisphosphonic acids of various lengths, L1–L3, were first synthesized starting from 1,1′-bi-2-naphthol (BINOL) in multi-step sequences. Amorphous chiral porous zirconium phosphonates were then obtained by refluxing BINOL-derived bisphosphonic acids with Zr(OnBu)4 in n-BuOH, and have been characterized by powder X-ray diffraction, solid-state CP-MAS NMR, IR, TGA, adsorption measurements, circular dichroism spectroscopy, and microanalyses. These zirconium phosphonates have empirical formulae of (Zr-L1–3)·xH2O (x=4 or 5), and exhibit BET surface areas ranging from 431 to 586 m2/g. In combination with Ti(OiPr)4, these zirconium phosphonates have been used to heterogeneously catalyze the additions of diethylzinc to a wide range of aromatic aldehydes with high conversions and e.e. of up to 72%. This work represents a novel approach towards heterogeneous asymmetric catalysis. The tunability of such a molecular building block approach promises to lead to practically useful heterogeneous asymmetric catalytic processes.Chiral porous solids based on BINOL-derived Zr phosphonates have been synthesized via a molecular building block approach, whose dihydroxy functionalities coordinate to Ti(IV) centers to form active catalysts for the asymmetric additions of diethylzinc to aromatic aldehydes with high conversions and e.e. values of up to 72%.
Co-reporter:Aiguo Hu Dr.;Helen L. Ngo
Angewandte Chemie 2004 Volume 116(Issue 9) pp:
Publication Date(Web):18 FEB 2004
DOI:10.1002/ange.200490025
Co-reporter:Aiguo Hu Dr.;Helen L. Ngo
Angewandte Chemie International Edition 2004 Volume 43(Issue 19) pp:
Publication Date(Web):28 APR 2004
DOI:10.1002/anie.200353415
A family of chiral diphosphanes with systematically tunable electronic and steric properties have been used in the asymmetric hydrogenation of β-aryl ketoesters with excellent ee values (up to 99.8 %) by taking advantage of remarkable 4,4′-substituent effects on binap. These highly enantioselective Ru catalysts have also been effectively immobilized in room-temperature ionic liquids (RTIL).
Co-reporter:Aiguo Hu Dr.;Helen L. Ngo
Angewandte Chemie International Edition 2004 Volume 43(Issue 9) pp:
Publication Date(Web):18 FEB 2004
DOI:10.1002/anie.200490025
Co-reporter:Helen L. Ngo, Aiguo Hu and Wenbin Lin
Chemical Communications 2003 (Issue 15) pp:1912-1913
Publication Date(Web):26 Jun 2003
DOI:10.1039/B302637J
Polar phosphonic acid-derived Ru-BINAP systems were used to catalyze asymmetric hydrogenation of β-keto esters in room temperature ionic liquids (RTILs) with complete conversions and ee values higher than those obtained from homogeneous reactions in MeOH (up to 99.3%), and were recycled by simple extraction and used for four times without the loss of activity and enantioselectivity.
Co-reporter:Yong Cui, Helen L. Ngo and Wenbin Lin
Chemical Communications 2003 (Issue 12) pp:1388-1389
Publication Date(Web):16 May 2003
DOI:10.1039/B212781D
A homochiral triple helix was self-assembled from an axially chiral bipyridine and a linear metal-connecting point, which further assembles into a 2D network via infinite π⋯π stacking interactions and acts as a host for the inclusion of guest molecules.
Co-reporter:Hua Jiang, Aiguo Hu and Wenbin Lin
Chemical Communications 2003 (Issue 1) pp:96-97
Publication Date(Web):03 Dec 2002
DOI:10.1039/B208324H
Chiral metallacyclophanes were self-assembled from cis-(PEt3)2PtCl2 and enantiopure atropisomeric 1,1′-binaphthyl-6,6′-bis(acetylenes) and used in highly enantioselective catalytic diethylzinc additions to aldehydes to afford chiral secondary alcohols.
Co-reporter:Suk Joong Lee, Charles R. Luman, Felix N. Castellano and Wenbin Lin
Chemical Communications 2003 (Issue 17) pp:2124-2125
Publication Date(Web):29 Jul 2003
DOI:10.1039/B307727F
Chiral molecular squares based on the Pt–alkynyl linkage were synthesized via stepwise directed assembly, and exhibit interesting dual luminescence at room temperature which is potentially exploitable for chiral sensory applications.
Co-reporter:Yong Cui, Helen L. Ngo, Peter S. White and Wenbin Lin
Chemical Communications 2003 (Issue 8) pp:994-995
Publication Date(Web):18 Mar 2003
DOI:10.1039/B211916A
Homochiral 3D open frameworks have been assembled from 1- and 2-D coordination structures via hydrogen bonding and are stable towards the removal of included guest molecules.
Co-reporter:Aiguo Hu Dr.;Helen L. Ngo
Angewandte Chemie International Edition 2003 Volume 42(Issue 48) pp:
Publication Date(Web):10 DEC 2003
DOI:10.1002/anie.200351264
Catalytic building blocks: Chiral porous zirconium phosphonates containing Ru-binap moieties are synthesized by a molecular building-block approach, and characterized by a variety of techniques. These hybrid solids are used for enantioselective heterogeneous asymmetric hydrogenation of β-keto esters with ee values of up to 95 % (see picture). Ready tunability of such a molecular building-block approach promises to lead to useful heterogeneous asymmetric catalysts.
Co-reporter:Aiguo Hu Dr.;Helen L. Ngo
Angewandte Chemie 2003 Volume 115(Issue 48) pp:
Publication Date(Web):10 DEC 2003
DOI:10.1002/ange.200351264
Katalysatoren aus Komponenten: Chirale poröse Zirconiumphosphonate mit Ru(binap)-Einheiten wurden nach dem Baukastenprinzip aus molekularen Komponenten aufgebaut. Diese analytisch charakterisierten Hybridmaterialien katalysieren die enantioselektive asymmetrische Hydrierung von β-Ketoestern mit bis zu 95 % ee (siehe Bild). Das Baukastenverfahren sollte die gezielte Entwicklung nutzbringender Heterogenkatalysatoren für asymmetrische Synthesen ermöglichen.
Co-reporter:Yong Cui, Helen L. Ngo, Peter S. White and Wenbin Lin
Chemical Communications 2002 (Issue 16) pp:1666-1667
Publication Date(Web):08 Jul 2002
DOI:10.1039/B204249E
Homochiral 3D metal–organic open frameworks based on enantiopure atropisomeric dicarboxylic acid bridging ligands and dilanthanide secondary building units exhibit an unprecedented 4966 topology, and possess ethoxy-protected BINOL functionalities that are pointing toward the open channels.
Co-reporter:Hua Jiang, Suk Joong Lee and Wenbin Lin
Dalton Transactions 2002 (Issue 18) pp:3429-3433
Publication Date(Web):16 Aug 2002
DOI:10.1039/B206159G
The new chiral ligand 4′-[6-(2,2′-diethoxy-1,1′-binaphthyl)]-2,2′:6′,2″-terpyridine (L1) was synthesized in three steps in 47% overall yield starting from 6,6′-dibromo-2,2′-diethoxy-1,1′-binaphthalene. L1 was quantitatively converted to 4′-[6-(2,2′-dihydroxy-1,1′-binaphthyl)]-2,2′:6′,2″-terpyridine (L2) by treatment with BBr3, while L2 was treated with tert-butyldimethylsilyl chloride to give to 4′-{6-[2,2′-bis(tert-butyldimethylsiloxy)-1,1′-binaphthyl]}-2,2′:6′,2″-terpyridine (L3) in high yields. These new chiral terpyridine ligands L1–3 were coordinated to Ru(III) centers to generate Ru(L1–3)Cl3 which were then treated with the tetrakis(terpyridine) core in the presence of 4-ethylmorpholine to afford chiral Ru(terpy)22+ based metallodendrimers containing enantiopure 1,1′-bi-2-naphthyl units in their peripheries. These chiral metallodendrimers were characterized by NMR, ESI-MS, and cyclic voltammetry, while their photophysical properties were studied using UV-Vis, luminescence, and circular dichroism spectroscopies.
Co-reporter:Yong Cui Dr.;Owen R. Evans;Helen L. Ngo;Peter S. White Dr.
Angewandte Chemie 2002 Volume 114(Issue 7) pp:
Publication Date(Web):27 MAR 2002
DOI:10.1002/1521-3757(20020402)114:7<1207::AID-ANGE1207>3.0.CO;2-1
Ein chirales 2D-Koordinationsnetzwerk bildet die Grundstruktur eines Zeolith-ähnlichen porösen Feststoffes mit Metall-Carboxylat-Koordination. Zum Aufbau werden enantiomerenreine Dicarboxylat-Brückenliganden verwendet. Eine Ethoxy-geschützte BINOL-Funktionalität ragt in die chiralen Hohlräume (siehe Bild).
Co-reporter:Yong Cui Dr.;Owen R. Evans;Helen L. Ngo;Peter S. White Dr.
Angewandte Chemie International Edition 2002 Volume 41(Issue 7) pp:
Publication Date(Web):27 MAR 2002
DOI:10.1002/1521-3773(20020402)41:7<1159::AID-ANIE1159>3.0.CO;2-5
A chiral two-dimensional network is the basis for the structure of a homochiral solid exploiting metal–carboxylate coordination. The synthesis involved enantiopure bridging ligands and metal–organic secondary building units (SBUs), and resulted in ethoxy-protected BINOL functionalities pointing into the cavities in this crystalline chiral zeolitic material (see picture).
Co-reporter:Zhigang Xie ; Cheng Wang ; Kathryn E. deKrafft
Journal of the American Chemical Society () pp:
Publication Date(Web):January 28, 2011
DOI:10.1021/ja109166b
Porous cross-linked polymers (PCPs) with phosphorescent [Ru(bpy)3]2+ and [Ir(ppy)2(bpy)]+ building blocks were obtained via octacarbonyldicobalt (Co2(CO)8)-catalyzed alkyne trimerization reactions. The resultant Ru- and Ir-PCPs exhibited high porosity with specific surface areas of 1348 and 1547 m2/g, respectively. They are thermally stable at up to 350 °C in air and do not dissolve or decompose in all solvents tested, including concentrated hydrochloric acid. The photoactive PCPs were shown to be highly effective, recyclable, and reusable heterogeneous photocatalysts for aza-Henry reactions, α-arylation of bromomalonate, and oxyamination of an aldehyde, with catalytic activities comparable to those of the homogeneous [Ru(bpy)3]2+ and [Ir(ppy)2(bpy)]+ photocatalysts. This work highlights the potential of developing photoactive PCPs as highly stable, molecularly tunable, and recyclable and reusable heterogeneous photocatalysts for a variety of important organic transformations.
Co-reporter:Liang Wen, Peng Cheng and Wenbin Lin
Chemical Communications 2012 - vol. 48(Issue 23) pp:NaN2848-2848
Publication Date(Web):2012/01/27
DOI:10.1039/C2CC17298D
Exposure to CH2Cl2 at room temperature induces single-crystal to single-crystal transformation of the 2D coordination network [Zn2L(DMF)4]·2DMF·4H2O to the 3D metal–organic framework [Zn2L(H2O)2]·xsolv viadimerization of the metal-connecting points, leading to significant enhancement in framework stability, porosity, and H2 uptake capacity.
Co-reporter:Demin Liu, Stephanie A. Kramer, Rachel C. Huxford-Phillips, Shunzhi Wang, Joseph Della Rocca and Wenbin Lin
Chemical Communications 2012 - vol. 48(Issue 21) pp:NaN2670-2670
Publication Date(Web):2012/01/23
DOI:10.1039/C2CC17635A
Nanoscale coordination polymers containing exceptionally high loadings of bisphosphonates were coated with single lipid bilayers to control the drug release kinetics and functionalized with a targeting ligand to endow cell-targeting capability, leading to much enhanced cytotoxicity against human lung and pancreatic cancer cells.
Co-reporter:Feijie Song, Cheng Wang and Wenbin Lin
Chemical Communications 2011 - vol. 47(Issue 29) pp:NaN8258-8258
Publication Date(Web):2011/06/22
DOI:10.1039/C1CC12701B
A chiral metal–organic framework (MOF) of the lcy topology was constructed from the Mn–Salen derived dicarboxylic acid and the [Zn4(μ4-O)(O2CR)6] secondary building unit, and used in highly regio- and stereo-selective sequential alkene epoxidation/epoxide ring-opening reactions.
Co-reporter:Joseph M. Falkowski, Sophie Liu, Cheng Wang and Wenbin Lin
Chemical Communications 2012 - vol. 48(Issue 52) pp:NaN6510-6510
Publication Date(Web):2012/05/08
DOI:10.1039/C2CC32232C
A pair of interpenetrated and non-interpenetrated chiral metal–organic frameworks with the same catalytic sites but different open channel sizes catalysed asymmetric cyclopropanation of substituted terminal alkenes with excellent diastereoselectivities (up to 9.6) and enantioselectivities (up to >99%).
Co-reporter:Teng Zhang, Feijie Song and Wenbin Lin
Chemical Communications 2012 - vol. 48(Issue 70) pp:NaN8768-8768
Publication Date(Web):2012/07/13
DOI:10.1039/C2CC34033J
Chiral metal–organic frameworks built from a Co-salen derived dicarboxylate bridging ligand exhibited different regioselectivities from the corresponding homogeneous catalyst by shutting down bimolecular activation pathways.
Co-reporter:Nicholas A. Zafiropoulos, Helen L. Ngo, Thomas A. Foglia, Edward T. Samulski and Wenbin Lin
Chemical Communications 2007(Issue 35) pp:NaN3672-3672
Publication Date(Web):2007/06/27
DOI:10.1039/B704189F
Recyclable and reusable heterogeneous diarylammonium catalysts are highly effective in catalyzing the esterification of the free fatty acid (FFA) present in greases to methyl esters to reduce the FFA content from 12–40 wt% to 0.5–1 wt%; the resulting ester–glyceride mixture (pretreated grease) could then be readily converted to methyl esters by base-catalyzed transesterification.
Co-reporter:Michaël Carboni, Carter W. Abney, Shubin Liu and Wenbin Lin
Chemical Science (2010-Present) 2013 - vol. 4(Issue 6) pp:NaN2402-2402
Publication Date(Web):2013/04/04
DOI:10.1039/C3SC50230A
Three metal–organic frameworks (MOFs) of the UiO-68 network topology were prepared using the amino-TPDC or TPDC bridging ligands containing orthogonal phosphorylurea groups (TPDC is p,p′-terphenyldicarboxylic acid), and investigated for sorption of uranium from water and artificial seawater. The stable and porous phosphorylurea-derived MOFs were shown to be highly efficient in sorbing uranyl ions, with saturation sorption capacities as high as 217 mg U g−1 which is equivalent to binding one uranyl ion for every two sorbent groups. Coordination modes between uranyl groups and simplified phosphorylurea motifs were investigated by DFT calculations, revealing a thermodynamically favorable monodentate binding of two phosphorylurea ligands to one uranyl ion. Convergent orientation of phosphorylurea groups at appropriate distances inside the MOF cavities is believed to facilitate their cooperative binding with uranyl ions. This work represents the first application of MOFs as novel sorbents to extract actinide elements from aqueous media.
Co-reporter:Demin Liu, Haohan Wu, Shunzhi Wang, Zhigang Xie, Jing Li and Wenbin Lin
Chemical Science (2010-Present) 2012 - vol. 3(Issue 10) pp:NaN3037-3037
Publication Date(Web):2012/07/09
DOI:10.1039/C2SC20601C
A 6,8-connected 3-dimensional metal–organic framework (2) of the tph topology was constructed from a new aromatic-rich, tetraphenylmethane-derived octa-carboxylate bridging ligand and trizinc cluster secondary building units (SBUs), and exhibited exceptionally high hydrogen (58 mg g−1 and 39 g L−1 at 52 bar and 77 K) and methane (276 mg g−1 and 189 g L−1 at 80 bar and 298 K) uptake capacities. 2 has the highest hydrogen uptake at 298 K among all of the MOFs that have been examined to date. The gravimetric and volumetric methane uptake capacities for 2 are the highest among thousands of MOFs that have been evaluated. We attribute the exceptionally high gas uptake capacities of 2 to the highly branched, aromatic-rich nature of the bridging ligand, optimal pore size, and the open metal sites in the trizinc SBUs in a stable high-connectivity MOF.
Co-reporter:Rachel C. Huxford, Kathryn E. deKrafft, William S. Boyle, Demin Liu and Wenbin Lin
Chemical Science (2010-Present) 2012 - vol. 3(Issue 1) pp:NaN204-204
Publication Date(Web):2011/10/20
DOI:10.1039/C1SC00499A
Nanoscale coordination polymers (NCPs) have been demonstrated as an interesting platform for drug delivery, as they possess many advantages over small-molecule chemotherapeutics such as high payloads, lower systemic toxicity, tunability, and enhanced tumor uptake. Existing formulations for the delivery of methotrexate (MTX), an antifolate cancer drug, have very low drug loadings. Herein, we report the incorporation of MTX as a building block in an NCP formulation with exceptionally high drug loadings (up to 79.1 wt%) and the selective delivery of the NCP to cancer cells. Encapsulation of the NCP in a functionalized lipid bilayer allows for targeted delivery and controlled release to cancer cells. A phosphor can be doped into the NCPs for monitoring particle uptake by optical imaging. The lipid-coated and anisamide-targeted NCPs have superior in vitro efficacy against acute lymphoblastic leukemia cells when compared to the free drug.
Co-reporter:Liang Wen, Peng Cheng and Wenbin Lin
Chemical Science (2010-Present) 2012 - vol. 3(Issue 7) pp:NaN2292-2292
Publication Date(Web):2012/04/23
DOI:10.1039/C2SC20172K
Two high-connectivity MOFs with very interesting modes of mixed-motif interpenetration and cross-linking were synthesized using the elongated and aromatic-rich methanetetra(biphenyl-p-carboxylic acid) bridging ligand (H4MTBPC, H4L). [Zn4(L)(H2L)2]·12DEF·40H2O (1) contains an interpenetrating 4,8-connected 3D framework of the alb/P topology and 4,4-connected 3D network of the lon topology, whereas [Co5(L)(HL)2]·15DMF·37H2O (2) is the first 4,12-connected 4-nodal net with the Schläfli symbol of {422.639.85}{45.6}2{46}. The structure of 2 can be visualized as cross-linking of three 4,4-connected 3D networks of the lon topology. The seemingly different structures of 1 and 2 are in fact closely related as the structure of 1 can be obtained by removing one of the Co centers in the penta-cobalt secondary building unit (SBU). Unusual mixed-motif interpenetration in 1 and cross-linking in 2 rigidify and stabilize the frameworks, leading to highly porous MOFs with high uptake capacities for H2 and CO2.
Co-reporter:Juan L. Vivero-Escoto, Rachel C. Huxford-Phillips and Wenbin Lin
Chemical Society Reviews 2012 - vol. 41(Issue 7) pp:NaN2685-2685
Publication Date(Web):2012/01/10
DOI:10.1039/C2CS15229K
Nanoparticle-based contrast agents are attracting a great deal of attention for various biomedical imaging and theranostic applications. Compared to conventional contrast agents, nanoparticles possess several potential advantages to improve in vivo detection and to enhance targeting efficiency. Silica-based nanoprobes can be engineered to achieve longer blood circulation times, specific clearance pathways, and multivalent binding. In this tutorial review, we summarize the latest progress on designing silica-based nanoprobes for imaging and theranostic applications. The synthesis of both solid silica and mesoporous silica nanoparticles is described, along with different approaches used for surface functionalization. Special emphasis is placed on the application of silica-based nanoprobes in optical, magnetic resonance, and multimodal imaging. The latest breakthroughs in the applications of silica nanoparticles as theranostic agents are also highlighted.
Co-reporter:Liqing Ma, Carter Abney and Wenbin Lin
Chemical Society Reviews 2009 - vol. 38(Issue 5) pp:NaN1256-1256
Publication Date(Web):2009/02/23
DOI:10.1039/B807083K
This tutorial review presents recent developments of homochiral metal–organic frameworks (MOFs) in enantioselective catalysis. Following a brief introduction of the basic concepts and potential virtues of MOFs in catalysis, we summarize three distinct strategies that have been utilized to synthesize homochiral MOFs. Framework stability and accessibility of the open channels to reagents are then addressed. We finally survey recent successful examples of catalytically active homochiral MOFs based on three approaches, namely, homochiral MOFs with achiral catalytic sites, incorporation of asymmetric catalysts directly into the framework, and post-synthetic modification of homochiral MOFs. Although still in their infancy, homochiral MOFs have clearly demonstrated their utility in heterogeneous asymmetric catalysis, and a bright future is foreseen for the development of practically useful homochiral MOFs in the production of optically pure organic molecules.
Co-reporter:Kathryn E. deKrafft, William S. Boyle, Laurel M. Burk, Otto Z. Zhou and Wenbin Lin
Journal of Materials Chemistry A 2012 - vol. 22(Issue 35) pp:NaN18144-18144
Publication Date(Web):2012/06/07
DOI:10.1039/C2JM32299D
Nanoscale metal–organic frameworks (NMOFs) of the UiO-66 structure containing high Zr (37 wt%) and Hf (57 wt%) content were synthesized and characterized, and their potential as contrast agents for X-ray computed tomography (CT) imaging was evaluated. Hf-NMOFs of different sizes were coated with silica and poly(ethylene glycol) (PEG) to enhance biocompatibility, and were used for in vivo CT imaging of mice, showing increased attenuation in the liver and spleen.
Co-reporter:Kathryn M. L. Taylor and Wenbin Lin
Journal of Materials Chemistry A 2009 - vol. 19(Issue 35) pp:NaN6422-6422
Publication Date(Web):2009/05/18
DOI:10.1039/B900866G
Lanthanide luminescence is a common method for the detection of dipicolinic acid (DPA), a chemical marker for bacterial spores. In this paper we report the development of silica nanoparticle based luminescent sensors for DPA detection. The sensors consist of three different modified EDTA–Tb complexes immobilized on 37 nm solid silica nanoparticles. The use of a nanoparticle platform also allows for the incorporation of an internal reference which eliminates the need for instrument-specific calibration curves for DPA quantification in an analyte. Limits of detection on the order of nanomolar concentrations can be achieved using these nanoparticle based DPA luminescence sensors.
