Co-reporter:Robinson W. Flaig, Thomas M. Osborn Popp, Alejandro M. Fracaroli, Eugene A. Kapustin, Markus J. Kalmutzki, Rashid M. Altamimi, Farhad Fathieh, Jeffrey A. Reimer, and Omar M. Yaghi
Journal of the American Chemical Society September 6, 2017 Volume 139(Issue 35) pp:12125-12125
Publication Date(Web):August 17, 2017
DOI:10.1021/jacs.7b06382
The use of two primary alkylamine functionalities covalently tethered to the linkers of IRMOF-74-III results in a material that can uptake CO2 at low pressures through a chemisorption mechanism. In contrast to other primary amine-functionalized solid adsorbents that uptake CO2 primarily as ammonium carbamates, we observe using solid state NMR that the major chemisorption product for this material is carbamic acid. The equilibrium of reaction products also shifts to ammonium carbamate when water vapor is present; a new finding that has impact on control of the chemistry of CO2 capture in MOF materials and one that highlights the importance of geometric constraints and the mediating role of water within the pores of MOFs.
Co-reporter:Yingbo Zhao, Lei Guo, Felipe Gándara, Yanhang Ma, Zheng Liu, Chenhui Zhu, Hao Lyu, Christopher A. Trickett, Eugene A. Kapustin, Osamu Terasaki, and Omar M. Yaghi
Journal of the American Chemical Society September 20, 2017 Volume 139(Issue 37) pp:13166-13166
Publication Date(Web):August 28, 2017
DOI:10.1021/jacs.7b07457
Developing synthetic methodology to crystallize extended covalent structures has been an important pursuit of reticular chemistry. Here, we report a homogeneous synthetic route for imine covalent organic frameworks (COFs) where crystallites emerge from clear solutions without forming amorphous polyimine precipitates. The key feature of this route is the utilization of tert-butyloxycarbonyl group protected amine building blocks, which are deprotected in situ and gradually nucleate the crystalline framework. We demonstrate the utility of this approach by crystallizing a woven covalent organic framework (COF-112), in which covalent organic threads are interlaced to form a three-dimensional woven framework. The homogeneous imine COF synthesis also enabled the control of nucleation and crystal growth leading to uniform nanocrystals, through microwave-assisted reactions, and facile preparation of oriented thin films.
Co-reporter:Kairat Sabyrov, Juncong Jiang, Omar. M. Yaghi, and Gabor A. Somorjai
Journal of the American Chemical Society September 13, 2017 Volume 139(Issue 36) pp:12382-12382
Publication Date(Web):August 25, 2017
DOI:10.1021/jacs.7b06629
Exceptionally high surface area and ordered nanopores of a metal–organic framework (MOF) are exploited to encapsulate and homogeneously disperse a considerable amount of phosphotungstic acid (PTA). When combined with platinum nanoparticles positioned on the external surface of the MOF, the construct shows a high catalytic activity for hydroisomerization of n-hexane, a reaction requiring hydrogenation/dehydrogenation and moderate to strong Brønsted acid sites. Characterization of the catalytic activity and acidic sites as a function of PTA loading demonstrates that both the concentration and strength of acidic sites are highest for the catalyst with the largest amount of PTA. The MOF construct containing 60% PTA by weight produces isoalkanes with 100% selectivity and 9-fold increased mass activity as compared to a more traditional aluminosilicate catalyst, further demonstrating the capacity of the MOF to contain a high concentration of active sites necessary for the isomerization reaction.
Co-reporter:Bassem A. Al-Maythalony, Ahmed M. Alloush, Muhammed Faizan, Hatim Dafallah, Mohammed A. A. Elgzoly, Adam A. A. Seliman, Amir Al-Ahmed, Zain H. Yamani, Mohamed A. M. Habib, Kyle E. Cordova, and Omar M. Yaghi
Nanoparticles of zeolitic imidazolate framework-7 (nZIF-7) were blended with poly(ether imide) (PEI) to fabricate a new mixed-matrix membrane (nZIF-7/PEI). nZIF-7 was chosen in order to demonstrate the power of postsynthetic modification (PSM) by linker exchange of benzimidazolate to benzotriazolate for tuning the permeability and selectivity properties of a resulting membrane (PSM-nZIF-7/PEI). These two new membranes were subjected to constant volume, variable pressure gas permeation measurements (H2, N2, O2, CH4, CO2, C2H6, and C3H8), in which unique gas separation behavior was observed when compared to the pure PEI membrane. Specifically, the nZIF-7/PEI membrane exhibited the highest selectivities for CO2/CH4, CO2/C2H6, and CO2/C3H8 gas pairs. Furthermore, PSM-nZIF-7/PEI membrane displayed the highest permeabilities, which resulted in H2/CH4, N2/CH4, and H2/CO2 permselectivities that are remarkably well-positioned on the Robeson upper bound curves, thus, indicating its potential applicability for use in practical gas purifications.Keywords: gas separation; metal−organic frameworks; mixed-matrix membranes; nanomaterials; zeolitic imidazolate frameworks;
Co-reporter:Jingjing Yang, Yue-Biao Zhang, Qi Liu, Christopher A. Trickett, Enrique Gutiérrez-Puebla, M. Ángeles Monge, Hengjiang Cong, Abdulrahman Aldossary, Hexiang Deng, and Omar M. Yaghi
Journal of the American Chemical Society May 10, 2017 Volume 139(Issue 18) pp:6448-6448
Publication Date(Web):April 11, 2017
DOI:10.1021/jacs.7b02272
We report three design principles for obtaining extra-large pore openings and cages in the metal–organic analogues of inorganic zeolites, zeolitic imidazolate frameworks (ZIFs). Accordingly, we prepared a series of 15 ZIFs, members of which have the largest pore opening (22.5 Å) and the largest cage size (45.8 Å) known for all porous tetrahedral structures. The key parameter allowing us to access these exceptional ZIFs is what we define as the steric index (δ), which is related to the size and shape of the imidazolate linkers employed in the synthesis. The three principles are based on using multiple linkers with specific range and ratios of δ to control the size of rings and cages from small to large, and therefore are universally applicable to all existing ZIFs. The ZIF with the largest cage size (ZIF-412) shows the best selectivity of porous materials tested toward removal of octane and p-xylene from humid air.
Co-reporter:Thomas M. Osborn Popp and Omar M. Yaghi
Accounts of Chemical Research March 21, 2017 Volume 50(Issue 3) pp:532-532
Publication Date(Web):March 21, 2017
DOI:10.1021/acs.accounts.6b00529
Sequence-dependent materials are a class of materials in which a compositionally aperiodic apportionment of functional groups leads to properties where the whole performs better than the sum of the parts. Here, we discuss what defines a sequence-dependent material, and how the concept can be realized in crystals of extended structures such as metal–organic frameworks.
Co-reporter:Eugene A. Kapustin, Seungkyu Lee, Ahmad S. Alshammari, and Omar M. Yaghi
ACS Central Science June 28, 2017 Volume 3(Issue 6) pp:662-662
Publication Date(Web):June 7, 2017
DOI:10.1021/acscentsci.7b00169
Despite numerous studies on chemical and thermal stability of metal–organic frameworks (MOFs), mechanical stability remains largely undeveloped. To date, no strategy exists to control the mechanical deformation of MOFs under ultrahigh pressure. Here, we show that the mechanically unstable MOF-520 can be retrofitted by precise placement of a rigid 4,4′-biphenyldicarboxylate (BPDC) linker as a “girder” to afford a mechanically robust framework: MOF-520-BPDC. This retrofitting alters how the structure deforms under ultrahigh pressure and thus leads to a drastic enhancement of its mechanical robustness. While in the parent MOF-520 the pressure transmitting medium molecules diffuse into the pore and expand the structure from the inside upon compression, the girder in the new retrofitted MOF-520-BPDC prevents the framework from expansion by linking two adjacent secondary building units together. As a result, the modified MOF is stable under hydrostatic compression in a diamond-anvil cell up to 5.5 gigapascal. The increased mechanical stability of MOF-520-BPDC prohibits the typical amorphization observed for MOFs in this pressure range. Direct correlation between the orientation of these girders within the framework and its linear strain was estimated, providing new insights for the design of MOFs with optimized mechanical properties.
Co-reporter:Jingjing Yang, Christopher A. Trickett, Salman B. Alahmadi, Ahmad S. Alshammari, and Omar M. Yaghi
Journal of the American Chemical Society June 21, 2017 Volume 139(Issue 24) pp:8118-8118
Publication Date(Web):June 4, 2017
DOI:10.1021/jacs.7b04542
Two porous, chiral metal–organic frameworks (MOFs), Ca14(l-lactate)20(acetate)8(C2H5OH)(H2O) (MOF-1201) and Ca6(l-lactate)3(acetate)9(H2O) (MOF-1203), are constructed from Ca2+ ions and l-lactate [CH3CH(OH)COO–], where Ca2+ ions are bridged by the carboxylate and hydroxyl groups of lactate and the carboxylate group of acetate to give a three-dimensional arrangement of Ca(−COO, −OH) polyhedra supporting one-dimensional pores with apertures and internal diameters of 7.8 and 9.6 Å (MOF-1201) and 4.6 and 5.6 Å (MOF-1203), respectively. These MOFs represent the first examples of extended porous structures based on Ca2+ and lactate. They show permanent porosity of 430 and 160 m2 g–1, respectively, and can encapsulate an agriculturally important fumigant, cis-1,3-dichloropropene. MOF-1201 shows a 100 times lower release rate compared with liquid cis-1,3-dichloropropene under the same test conditions (25 °C, air flow rate of 1 cm3 min–1). The hydrolysis of MOF-1201 in water makes it the first example of a degradable porous solid carrier for such fumigants.
Co-reporter:Shankar Narayanan;Sungwoo Yang;Sameer R. Rao;Ari S. Umans;Hiroyasu Furukawa;Evelyn N. Wang;Eugene A. Kapustin;Hyunho Kim
Science 2017 Volume 356(Issue 6336) pp:
Publication Date(Web):
DOI:10.1126/science.aam8743
Solar heat helps harvest humidity
Atmospheric humidity and droplets constitute a huge freshwater resource, especially at the low relative humidity (RH) levels typical of arid environments. Water can be adsorbed by microporous materials such as zeolites, but often, making these materials release the water requires too much energy to be practical. Kim et al. used a metal-organic framework (MOF) material that has a steep increase in water uptake over a narrow RH range to harvest water, using only ambient sunlight to heat the material. They obtained 2.8 liters of water per kilogram of MOF daily at 20% RH.
Covalent molecular frameworks are crystalline microporous materials assembled from organic molecules through strong covalent bonds in a process termed reticular synthesis. Diercks and Yaghi review developments in this area, noting the parallels between framework assembly and the covalent assembly of atoms into molecules, as described just over a century ago by Lewis. Emerging challenges include functionalization of existing frameworks and the creation of flexible materials through the design of woven structures.
Co-reporter:Bunyarat Rungtaweevoranit;Christian S. Diercks;Markus J. Kalmutzki;Omar M. Yaghi
Faraday Discussions 2017 (Volume 201) pp:9-45
Publication Date(Web):2017/09/06
DOI:10.1039/C7FD00160F
Reticular chemistry, the linking of molecular building units by strong bonds to make crystalline, extended structures such as metal–organic frameworks (MOFs), zeolitic imidazolate frameworks (ZIFs), and covalent organic frameworks (COFs), is currently one of the most rapidly expanding fields of science. In this contribution, we outline the origins of the field; the key intellectual and practical contributions, which have led to this expansion; and the new directions reticular chemistry is taking that are changing the way we think about making new materials and the manner with which we incorporate chemical information within structures to reach additional levels of functionality. This progress is described in the larger context of chemistry and unexplored, yet important, aspects of this field are presented.
Reticular chemistry, linking molecular building blocks together by strong bonds to make porous frameworks, is a rapidly expanding field of research, engaging laboratories worldwide. However, as with any emerging field, there exist ‘folklores’ permeating through the scientific discourse. These folklores do little in the way of advancing the field and, in no uncertain terms, negatively color our scientific pursuits. It is within this context that we seek to bring the folklores out into the open to provide the true realities of reticular chemistry.
We show that the activity and selectivity of Cu catalyst can be promoted by a Zr-based metal–organic framework (MOF), Zr6O4(OH)4(BDC)6 (BDC = 1,4-benzenedicarboxylate), UiO-66, to have a strong interaction with Zr oxide [Zr6O4(OH)4(−CO2)12] secondary building units (SBUs) of the MOF for CO2 hydrogenation to methanol. These interesting features are achieved by a catalyst composed of 18 nm single Cu nanocrystal (NC) encapsulated within single crystal UiO-66 (Cu⊂UiO-66). The performance of this catalyst construct exceeds the benchmark Cu/ZnO/Al2O3 catalyst and gives a steady 8-fold enhanced yield and 100% selectivity for methanol. The X-ray photoelectron spectroscopy data obtained on the surface of the catalyst show that Zr 3d binding energy is shifted toward lower oxidation state in the presence of Cu NC, suggesting that there is a strong interaction between Cu NC and Zr oxide SBUs of the MOF to make a highly active Cu catalyst.Keywords: CO2 hydrogenation; heterogeneous catalyst; metal nanocrystal; Metal−organic framework; methanol; strong metal−support interaction;
Co-reporter:Yingbo Zhao, Seung-Yul Lee, Nigel Becknell, Omar M. Yaghi, and C. Austen Angell
Journal of the American Chemical Society 2016 Volume 138(Issue 34) pp:10818-10821
Publication Date(Web):August 18, 2016
DOI:10.1021/jacs.6b07078
While glassy materials can be made from virtually every class of liquid (metallic, molecular, covalent, and ionic), to date, formation of glasses in which structural units impart porosity on the nanoscopic level remains undeveloped. In view of the well-established porosity of metal–organic frameworks (MOFs) and the flexibility of their design, we have sought to combine their formation principles with the general versatility of glassy materials. Although the preparation of glassy MOFs can be achieved by amorphization of crystalline frameworks, transparent glassy MOFs exhibiting permanent porosity accessible to gases are yet to be reported. Here, we present a generalizable chemical strategy for making such MOF glasses by assembly from viscous solutions of metal node and organic strut and subsequent evaporation of a plasticizer–modulator solvent. This process yields glasses with 300 m2/g internal surface area (obtained from N2 adsorption isotherms) and a 2 nm pore–pore separation. On a volumetric basis, this porosity (0.33 cm3/cm3) is 3 times that of the early MOFs (0.11 cm3/cm3 for MOF-2) and within range of the most porous MOFs known (0.60 cm3/cm3 for MOF-5). We believe the porosity originates from a 3D covalent network as evidenced by the disappearance of the glass transition signature as the solvent is removed and the highly cross-linked nanostructure builds up. Our work represents an important step forward in translating the versatility and porosity of MOFs to glassy materials.
Co-reporter:Peter J. Waller, Steven J. Lyle, Thomas M. Osborn Popp, Christian S. Diercks, Jeffrey A. Reimer, and Omar M. Yaghi
Journal of the American Chemical Society 2016 Volume 138(Issue 48) pp:15519-15522
Publication Date(Web):November 15, 2016
DOI:10.1021/jacs.6b08377
The imine linkages of two layered, porous covalent organic frameworks (COFs), TPB-TP-COF ([C6H3(C6H4N)3]2[C6H4(CH)2]3, 1) and 4PE-1P-COF ([C2(C6H4N)4][C6H4(CH)2]2, 2), have been transformed into amide linkages to make the respective isostructural amide COFs 1′ and 2′ by direct oxidation with retention of crystallinity and permanent porosity. Remarkably, the oxidation of both imine COFs is complete, as assessed by FT-IR and 13C CP-MAS NMR spectroscopy and demonstrates (a) the first chemical conversion of a COF linkage and (b) how the usual “crystallization problem” encountered in COF chemistry can be bypassed to access COFs, such as these amides, that are typically thought to be difficult to obtain by the usual de novo methods. The amide COFs show improved chemical stability relative to their imine progenitors.
Co-reporter:Kyung Min Choi, Dohyung Kim, Bunyarat Rungtaweevoranit, Christopher A. Trickett, Jesika Trese Deniz Barmanbek, Ahmad S. Alshammari, Peidong Yang, and Omar M. Yaghi
Journal of the American Chemical Society 2016 Volume 139(Issue 1) pp:356-362
Publication Date(Web):November 26, 2016
DOI:10.1021/jacs.6b11027
Materials development for artificial photosynthesis, in particular, CO2 reduction, has been under extensive efforts, ranging from inorganic semiconductors to molecular complexes. In this report, we demonstrate a metal–organic framework (MOF)-coated nanoparticle photocatalyst with enhanced CO2 reduction activity and stability, which stems from having two different functional units for activity enhancement and catalytic stability combined together as a single construct. Covalently attaching a CO2-to-CO conversion photocatalyst ReI(CO)3(BPYDC)Cl, BPYDC = 2,2′-bipyridine-5,5′-dicarboxylate, to a zirconium MOF, UiO-67 (Ren-MOF), prevents dimerization leading to deactivation. By systematically controlling its density in the framework (n = 0, 1, 2, 3, 5, 11, 16, and 24 complexes per unit cell), the highest photocatalytic activity was found for Re3-MOF. Structural analysis of Ren-MOFs suggests that a fine balance of proximity between photoactive centers is needed for cooperatively enhanced photocatalytic activity, where an optimum number of Re complexes per unit cell should reach the highest activity. Based on the structure–activity correlation of Ren-MOFs, Re3-MOF was coated onto Ag nanocubes (Ag⊂Re3-MOF), which spatially confined photoactive Re centers to the intensified near-surface electric fields at the surface of Ag nanocubes, resulting in a 7-fold enhancement of CO2-to-CO conversion under visible light with long-term stability maintained up to 48 h.
Co-reporter:Ha L. Nguyen; Felipe Gándara; Hiroyasu Furukawa; Tan L. H. Doan; Kyle E. Cordova
Journal of the American Chemical Society 2016 Volume 138(Issue 13) pp:4330-4333
Publication Date(Web):March 21, 2016
DOI:10.1021/jacs.6b01233
A crystalline material with a two-dimensional structure, termed metal–organic framework-901 (MOF-901), was prepared using a strategy that combines the chemistry of MOFs and covalent–organic frameworks (COFs). This strategy involves in situ generation of an amine-functionalized titanium oxo cluster, Ti6O6(OCH3)6(AB)6 (AB = 4-aminobenzoate), which was linked with benzene-1,4-dialdehyde using imine condensation reactions, typical of COFs. The crystal structure of MOF-901 is composed of hexagonal porous layers that are likely stacked in staggered conformation (hxl topology). This MOF represents the first example of combining metal cluster chemistry with dynamic organic covalent bond formation to give a new crystalline, extended framework of titanium metal, which is rarely used in MOFs. The incorporation of Ti(IV) units made MOF-901 useful in the photocatalyzed polymerization of methyl methacrylate (MMA). The resulting polyMMA product was obtained with a high-number-average molar mass (26 850 g mol–1) and low polydispersity index (1.6), which in many respects are better than those achieved by the commercially available photocatalyst (P-25 TiO2). Additionally, the catalyst can be isolated, reused, and recycled with no loss in performance.
Co-reporter:Noelle R. Catarineu, Alexander Schoedel, Philipp Urban, Maureen B. Morla, Christopher A. Trickett, and Omar M. Yaghi
Journal of the American Chemical Society 2016 Volume 138(Issue 34) pp:10826-10829
Publication Date(Web):August 12, 2016
DOI:10.1021/jacs.6b07267
Structural diversity of metal–organic frameworks (MOFs) has been largely limited to linkers with at most two different types of coordinating groups. MOFs constructed from linkers with three or more nonidentical coordinating groups have not been explored. Here, we report a robust and porous crystalline MOF, Zn3(PBSP)2 or MOF-910, constructed from a novel linker PBSP (phenylyne-1-benzoate, 3-benzosemiquinonate, 5-oxidopyridine) bearing three distinct types of coordinative functionality. The MOF adopts a complex and previously unreported topology termed tto. Our study suggests that simple, symmetric linkers are not a necessity for formation of crystalline extended structures and that new, more complex topologies are attainable with irregular, heterotopic linkers. This work illustrates two principles of reticular chemistry: first, selectivity for helical over straight rod secondary building units (SBUs) is achievable with polyheterotopic linkers, and second, the pitch of the resulting helical SBUs may be fine-tuned based on the metrics of the polyheterotopic linker.
Co-reporter:Juncong Jiang, Hiroyasu Furukawa, Yue-Biao Zhang, and Omar M. Yaghi
Journal of the American Chemical Society 2016 Volume 138(Issue 32) pp:10244-10251
Publication Date(Web):July 21, 2016
DOI:10.1021/jacs.6b05261
High methane storage capacity in porous materials is important for the design and manufacture of vehicles powered by natural gas. Here, we report the synthesis, crystal structures and methane adsorption properties of five new zinc metal–organic frameworks (MOFs), MOF-905, MOF-905-Me2, MOF-905-Naph, MOF-905-NO2, and MOF-950. All these MOFs consist of the Zn4O(−CO2)6 secondary building units (SBUs) and benzene-1,3,5-tri-β-acrylate, BTAC. The permanent porosity of all five materials was confirmed, and their methane adsorption measured up to 80 bar to reveal that MOF-905 is among the best performing methane storage materials with a volumetric working capacity (desorption at 5 bar) of 203 cm3 cm–3 at 80 bar and 298 K, a value rivaling that of HKUST-1 (200 cm3 cm–3), the benchmark compound for methane storage in MOFs. This study expands the scope of MOF materials with ultrahigh working capacity to include linkers having the common acrylate connectivity.
Journal of the American Chemical Society 2016 Volume 138(Issue 10) pp:3255-3265
Publication Date(Web):February 10, 2016
DOI:10.1021/jacs.5b10666
Linking molecular building units by covalent bonds to make crystalline extended structures has given rise to metal–organic frameworks (MOFs) and covalent organic frameworks (COFs), thus bringing the precision and versatility of covalent chemistry beyond discrete molecules to extended structures. The key advance in this regard has been the development of strategies to overcome the “crystallization problem”, which is usually encountered when attempting to link molecular building units into covalent solids. Currently, numerous MOFs and COFs are made as crystalline materials in which the large size of the constituent units provides for open frameworks. The molecular units thus reticulated become part of a new environment where they have (a) lower degrees of freedom because they are fixed into position within the framework; (b) well-defined spatial arrangements where their properties are influenced by the intricacies of the pores; and (c) ordered patterns onto which functional groups can be covalently attached to produce chemical complexity. The notion of covalent chemistry beyond molecules is further strengthened by the fact that covalent reactions can be carried out on such frameworks, with full retention of their crystallinity and porosity. MOFs are exemplars of how this chemistry has led to porosity with designed metrics and functionality, chemically-rich sequences of information within their frameworks, and well-defined mesoscopic constructs in which nanoMOFs enclose inorganic nanocrystals and give them new levels of spatial definition, stability, and functionality.
Co-reporter:Alejandro M. Fracaroli; Peter Siman; David A. Nagib; Mitsuharu Suzuki; Hiroyasu Furukawa; F. Dean Toste
Journal of the American Chemical Society 2016 Volume 138(Issue 27) pp:8352-8355
Publication Date(Web):June 27, 2016
DOI:10.1021/jacs.6b04204
The design of enzyme-like complexity within metal–organic frameworks (MOFs) requires multiple reactions to be performed on a MOF crystal without losing access to its interior. Here, we show that seven post-synthetic reactions can be successfully achieved within the pores of a multivariate MOF, MTV-IRMOF-74-III, to covalently incorporate tripeptides that resemble the active sites of enzymes in their spatial arrangement and compositional heterogeneity. These reactions build up H2N-Pro-Gly-Ala-CONHL and H2N-Cys-His-Asp-CONHL (where L = organic struts) amino acid sequences by covalently attaching them to the organic struts in the MOFs, without losing porosity or crystallinity. An enabling feature of this chemistry is that the primary amine functionality (−CH2NHBoc) of the original MOF is more reactive than the commonly examined aromatic amines (−NH2), and this allowed for the multi-step reactions to be carried out in tandem within the MOF. Preliminary findings indicate that the complexity thus achieved can affect reactions that were previously accomplished only in the presence of enzymes.
X-ray crystallography can be the definitive method for determining the structure and chirality of small organic molecules, but orientational disorder in the crystal can limit its resolution. Lee et al. used a chiral metal-organic framework containing formate ligands that can bind and align molecules covalently to reduce this motion (see the Perspective by Öhrström). The structure and absolute configuration—i.e., which spatial arrangement of atoms is the R or S isomer—of several organic molecules can thus be measured. These range from small molecules, such as methanol, to complex plant hormones, such as gibberellins that have eight stereocenters or jasmonic acid, whose absolute configuration had not previously been directly established.
Co-reporter:Bunyarat Rungtaweevoranit;Yingbo Zhao;Kyung Min Choi
Nano Research 2016 Volume 9( Issue 1) pp:47-58
Publication Date(Web):2016 January
DOI:10.1007/s12274-015-0970-0
Controlling the chemistry at the interface of nanocrystalline solids has been a challenge and an important goal to realize desired properties. Integrating two different types of materials has the potential to yield new functions resulting from cooperative effects between the two constituents. Metal–organic frameworks (MOFs) are unique in that they are constructed by linking inorganic units with organic linkers where the building units can be varied nearly at will. This flexibility has made MOFs ideal materials for the design of functional entities at interfaces and hence allowing control of properties. This review highlights the strategies employed to access synergistic functionality at the interface of nanocrystalline MOFs (nMOFs) and inorganic nanocrystals (NCs).
Woven fabrics are inherently flexible. Liu et al. created a molecular fabric analog using metal-organic frameworks (see the Perspective by Gutierrez-Puebla). Phenanthroline ligands on a copper metal complex directed the addition of organic linkers via imine bonds to create helical organic threads with woven texture. Removing the copper allowed the strands to slide against each other and increased the elasticity of the material 10-fold.
Co-reporter:Peter J. Waller, Felipe Gándara, and Omar M. Yaghi
Accounts of Chemical Research 2015 Volume 48(Issue 12) pp:3053
Publication Date(Web):November 18, 2015
DOI:10.1021/acs.accounts.5b00369
Linking organic molecules by covalent bonds into extended solids typically generates amorphous, disordered materials. The ability to develop strategies for obtaining crystals of such solids is of interest because it opens the way for precise control of the geometry and functionality of the extended structure, and the stereochemical orientation of its constituents. Covalent organic frameworks (COFs) are a new class of porous covalent organic structures whose backbone is composed entirely of light elements (B, C, N, O, Si) that represent a successful demonstration of how crystalline materials of covalent solids can be achieved. COFs are made by combination of organic building units covalently linked into extended structures to make crystalline materials. The attainment of crystals is done by several techniques in which a balance is struck between the thermodynamic reversibility of the linking reactions and their kinetics. This success has led to the expansion of COF materials to include organic units linked by these strong covalent bonds: B–O, C–N, B–N, and B–O–Si.Since the organic constituents of COFs, when linked, do not undergo significant change in their overall geometry, it has been possible to predict the structures of the resulting COFs, and this advantage has facilitated their characterization using powder X-ray diffraction (PXRD) techniques. It has also allowed for the synthesis of COF structures by design and for their formation with the desired composition, pore size, and aperture. In practice, the modeled PXRD pattern for a given expected COF is compared with the experimental one, and depending on the quality of the match, this is used as a starting point for solving and then refining the crystal structure of the target COF. These characteristics make COFs an attractive class of new porous materials. Accordingly, they have been used as gas storage materials for energy applications, solid supports for catalysis, and optoelectronic devices. A large and growing library of linkers amenable to the synthesis of COFs is now available, and new COFs and topologies made by reticular synthesis are being reported. Much research is also directed toward the development of new methods of linking organic building units to generate other crystalline COFs. These efforts promise not only new COF chemistry and materials, but also the chance to extend the precision of molecular covalent chemistry to extended solids.
Co-reporter:Nhung T. T. Nguyen; Hiroyasu Furukawa; Felipe Gándara; Christopher A. Trickett; Hyung Mo Jeong; Kyle E. Cordova
Journal of the American Chemical Society 2015 Volume 137(Issue 49) pp:15394-15397
Publication Date(Web):November 23, 2015
DOI:10.1021/jacs.5b10999
A series of three-dimensional (3D) extended metal catecholates (M-CATs) was synthesized by combining the appropriate metal salt and the hexatopic catecholate linker, H6THO (THO6– = triphenylene-2,3,6,7,10,11-hexakis(olate)) to give Fe(THO)·Fe(SO4) (DMA)3, Fe-CAT-5, Ti(THO)·(DMA)2, Ti-CAT-5, and V(THO)·(DMA)2, V-CAT-5 (where DMA = dimethylammonium). Their structures are based on the srs topology and are either a 2-fold interpenetrated (Fe-CAT-5 and Ti-CAT-5) or noninterpenetrated (V-CAT-5) porous anionic framework. These examples are among the first catecholate-based 3D frameworks. The single crystal X-ray diffraction structure of the Fe-CAT-5 shows bound sulfate ligands with DMA guests residing in the pores as counterions, and thus ideally suited for proton conductivity. Accordingly, Fe-CAT-5 exhibits ultrahigh proton conductivity (5.0 × 10–2 S cm–1) at 98% relative humidity (RH) and 25 °C. The coexistence of sulfate and DMA ions within the pores play an important role in proton conductivity as also evidenced by the lower conductivity values found for Ti-CAT-5 (8.2 × 10–4 S cm–1 at 98% RH and 25 °C), whose structure only contained DMA guests.
Co-reporter:Nikolay Kornienko; Yingbo Zhao; Christopher S. Kley; Chenhui Zhu; Dohyung Kim; Song Lin; Christopher J. Chang; Omar M. Yaghi◆;Peidong Yang◆
Journal of the American Chemical Society 2015 Volume 137(Issue 44) pp:14129-14135
Publication Date(Web):October 28, 2015
DOI:10.1021/jacs.5b08212
A key challenge in the field of electrochemical carbon dioxide reduction is the design of catalytic materials featuring high product selectivity, stability, and a composition of earth-abundant elements. In this work, we introduce thin films of nanosized metal–organic frameworks (MOFs) as atomically defined and nanoscopic materials that function as catalysts for the efficient and selective reduction of carbon dioxide to carbon monoxide in aqueous electrolytes. Detailed examination of a cobalt–porphyrin MOF, Al2(OH)2TCPP-Co (TCPP-H2 = 4,4′,4″,4‴-(porphyrin-5,10,15,20-tetrayl)tetrabenzoate) revealed a selectivity for CO production in excess of 76% and stability over 7 h with a per-site turnover number (TON) of 1400. In situ spectroelectrochemical measurements provided insights into the cobalt oxidation state during the course of reaction and showed that the majority of catalytic centers in this MOF are redox-accessible where Co(II) is reduced to Co(I) during catalysis.
Co-reporter:Kyung Min Choi; Kyungsu Na; Gabor A. Somorjai
Journal of the American Chemical Society 2015 Volume 137(Issue 24) pp:7810-7816
Publication Date(Web):May 29, 2015
DOI:10.1021/jacs.5b03540
Chemical environment control of the metal nanoparticles (NPs) embedded in nanocrystalline metal–organic frameworks (nMOFs) is useful in controlling the activity and selectivity of catalytic reactions. In this report, organic linkers with two functional groups, sulfonic acid (−SO3H, S) and ammonium (−NH3+, N), are chosen as strong and weak acidic functionalities, respectively, and then incorporated into a MOF [Zr6O4(OH)4(BDC)6 (BDC = 1,4-benzenedicarboxylate), termed UiO-66] separately or together in the presence of 2.5 nm Pt NPs to build a series of Pt NPs-embedded in UiO-66 (Pt⊂nUiO-66). We find that these chemical functionalities play a critical role in product selectivity and activity in the gas-phase conversion of methylcyclopentane (MCP) to acyclic isomer, olefins, cyclohexane, and benzene. Pt⊂nUiO-66-S gives the highest selectivity to C6-cyclic products (62.4% and 28.6% for cyclohexane and benzene, respectively) without acyclic isomers products. Moreover, its catalytic activity was doubled relative to the nonfunctionalized Pt⊂nUiO-66. In contrast, Pt⊂nUiO-66-N decreases selectivity for C6-cyclic products to <50% while increases the acyclic isomer selectivity to 38.6%. Interestingly, the Pt⊂nUiO-66-SN containing both functional groups gave different product selectivity than their constituents; no cyclohexane was produced, while benzene was the dominant product with olefins and acyclic isomers as minor products. All Pt⊂nUiO-66 catalysts with different functionalities remain intact and maintain their crystal structure, morphology, and chemical functionalities without catalytic deactivation after reactions over 8 h.
Co-reporter:Yingbo Zhao; Nikolay Kornienko; Zheng Liu; Chenhui Zhu; Shunsuke Asahina; Tsung-Rong Kuo; Wei Bao; Chenlu Xie; Alexander Hexemer; Osamu Terasaki; Peidong Yang
Journal of the American Chemical Society 2015 Volume 137(Issue 6) pp:2199-2202
Publication Date(Web):January 26, 2015
DOI:10.1021/ja512951e
We enclose octahedral silver nanocrystals (Ag NCs) in metal–organic frameworks (MOFs) to make mesoscopic constructs Oh-nano-Ag⊂MOF in which the interface between the Ag and the MOF is pristine and the MOF is ordered (crystalline) and oriented on the Ag NCs. This is achieved by atomic layer deposition of aluminum oxide on Ag NCs and addition of a tetra-topic porphyrin-based linker, 4,4′,4″,4‴-(porphyrin-5,10,15,20-tetrayl)tetrabenzoic acid (H4TCPP), to react with alumina and make MOF [Al2(OH)2TCPP] enclosures around Ag NCs. Alumina thickness is precisely controlled from 0.1 to 3 nm, thus allowing control of the MOF thickness from 10 to 50 nm. Electron microscopy and grazing angle X-ray diffraction confirm the order and orientation of the MOF by virtue of the porphyrin units being perpendicular to the planes of the Ag. We use surface-enhanced Raman spectroscopy to directly track the metalation process on the porphyrin and map the distribution of the metalated and unmetalated linkers on a single-nanoparticle level.
Co-reporter:Yue-Biao Zhang; Hiroyasu Furukawa; Nakeun Ko; Weixuan Nie; Hye Jeong Park; Satoshi Okajima; Kyle E. Cordova; Hexiang Deng; Jaheon Kim
Journal of the American Chemical Society 2015 Volume 137(Issue 7) pp:2641-2650
Publication Date(Web):February 3, 2015
DOI:10.1021/ja512311a
Metal–organic framework-177 (MOF-177) is one of the most porous materials whose structure is composed of octahedral Zn4O(−COO)6 and triangular 1,3,5-benzenetribenzoate (BTB) units to make a three-dimensional extended network based on the qom topology. This topology violates a long-standing thesis where highly symmetric building units are expected to yield highly symmetric networks. In the case of octahedron and triangle combinations, MOFs based on pyrite (pyr) and rutile (rtl) nets were expected instead of qom. In this study, we have made 24 MOF-177 structures with different functional groups on the triangular BTB linker, having one or more functionalities. We find that the position of the functional groups on the BTB unit allows the selection for a specific net (qom, pyr, and rtl), and that mixing of functionalities (-H, -NH2, and -C4H4) is an important strategy for the incorporation of a specific functionality (-NO2) into MOF-177 where otherwise incorporation of such functionality would be difficult. Such mixing of functionalities to make multivariate MOF-177 structures leads to enhancement of hydrogen uptake by 25%.
Co-reporter:Peter Siman, Christopher A. Trickett, Hiroyasu Furukawa and Omar M. Yaghi
Chemical Communications 2015 vol. 51(Issue 98) pp:17463-17466
Publication Date(Web):30 Sep 2015
DOI:10.1039/C5CC07578E
Metal–organic frameworks (MOFs) based purely on sodium are rare, typically due to large numbers of coordinating solvent ligands. We designed a tetratopic aspartate-based linker with flexible carboxylate groups to enhance framework stability. We report two new air-stable sodium MOFs, MOF-705 and MOF-706, comprising 2D sodium oxide sheets.
A modular synthetic approach is reported for the synthesis of heterometallic metal–organic complex arrays (MOCAs). Modules of four metal centers containing three different metals copper(II), nickel(II), platinum(II), or ruthenium(II) are prepared using a solid-phase polypeptide synthesis technique and then linked in solution to make MOCAs of eight metal centers as linear, T-branched, and H-branched compounds. The MOCA molecular topologies thus have specific unique linear and branched sequences of metals along the peptide backbone.
Co-reporter:Christopher A. Trickett;Dr. Kevin J. Gagnon;Seungkyu Lee;Dr. Felipe Gándara; Hans-Beat Bürgi; Omar M. Yaghi
Angewandte Chemie International Edition 2015 Volume 54( Issue 38) pp:11162-11167
Publication Date(Web):
DOI:10.1002/anie.201505461
Abstract
The identification and characterization of defects, on the molecular level, in metal-organic frameworks (MOFs) remain a challenge. With the extensive use of single-crystal X-ray diffraction (SXRD), the missing linker defects in the zirconium-based MOF UiO-66, Zr6O4(OH)4(C8H4O4)6, have been identified as water molecules coordinated directly to the zirconium centers. Charge balancing is achieved by hydroxide anions, which are hydrogen bonded within the pores of the framework. Furthermore, the precise nature of the defects and their concentration can be manipulated by altering the starting materials, synthesis conditions, and post-synthetic modifications.
Proceedings of the National Academy of Sciences 2015 112(18) pp:5591-5596
Publication Date(Web):April 21, 2015
DOI:10.1073/pnas.1416417112
Multiple organic functionalities can now be apportioned into nanoscale domains within a metal-coordinated framework, posing
the following question: how do we control the resulting combination of “heterogeneity and order”? Here, we report the creation
of a metal–organic framework, MOF-2000, whose two component types are incorporated in a 2:1 ratio, even when the ratio of
component types in the starting solution is varied by an order of magnitude. Statistical mechanical modeling suggests that
this robust 2:1 ratio has a nonequilibrium origin, resulting from kinetic trapping of component types during framework growth.
Our simulations show how other “magic number” ratios of components can be obtained by modulating the topology of a framework
and the noncovalent interactions between component types, a finding that may aid the rational design of functional multicomponent
materials.
The identification and characterization of defects, on the molecular level, in metal-organic frameworks (MOFs) remain a challenge. With the extensive use of single-crystal X-ray diffraction (SXRD), the missing linker defects in the zirconium-based MOF UiO-66, Zr6O4(OH)4(C8H4O4)6, have been identified as water molecules coordinated directly to the zirconium centers. Charge balancing is achieved by hydroxide anions, which are hydrogen bonded within the pores of the framework. Furthermore, the precise nature of the defects and their concentration can be manipulated by altering the starting materials, synthesis conditions, and post-synthetic modifications.
Co-reporter:Kyle E. Cordova, Hiroyasu Furukawa, and Omar M. Yaghi
ACS Central Science 2015 Volume 1(Issue 1) pp:18
Publication Date(Web):March 23, 2015
DOI:10.1021/acscentsci.5b00028
How do we build research capacity throughout the world and capture the great human potential? To us, the answer is rather straightforward: the time-honored tradition of scientific mentoring must be practiced on a wider scale across borders. Herein, we detail the necessity for expanding mentorship to a global scale and provide several important principles to be considered when designing, planning, and implementing programs and centers of research around the world.
Co-reporter:Omar M. Yaghi;Christopher J. Chang;Song Lin;Eva M. Nichols;Aubrey R. Paris;Peidong Yang;Nikolay Kornienko;Yingbo Zhao;Dohyung Kim;Yue-Biao Zhang;Christian S. Diercks
Science 2015 Volume 349(Issue 6253) pp:1208-1213
Publication Date(Web):11 Sep 2015
DOI:10.1126/science.aac8343
Improving cobalt catalysts
Tethering molecular catalysts together is a tried and trusted method for making them easier to purify and reuse. Lin et al. now show that the assembly of a covalent organic framework (COF) structure can also improve fundamental catalytic performance. They used cobalt porphyrin complexes as building blocks for a COF. The resulting material showed greatly enhanced activity for the aqueous electrochemical reduction of CO2 to CO.
The growth of nanocrystalline metal–organic frameworks (nMOFs) around metal nanocrystals (NCs) is useful in controlling the chemistry and metric of metal NCs. In this Letter, we show rare examples of nMOFs grown in monocrystalline form around metal NCs. Specifically, Pt NCs were subjected to reactions yielding Zr(IV) nMOFs [Zr6O4(OH)4(fumarate)6, MOF-801; Zr6O4(OH)4(BDC)6 (BDC = 1,4-benzenedicarboxylate), UiO-66; Zr6O4(OH)4(BPDC)6 (BPDC = 4,4′-biphenyldicarboxylate), UiO-67] as a single crystal within which the Pt NCs are embedded. These constructs (Pt⊂nMOF)nanocrystal are found to be active in gas-phase hydrogenative conversion of methylcyclopentane (MCP) and give unusual product selectivity. The Pt⊂nUiO-66 shows selectivity to C6-cyclic hydrocarbons such as cyclohexane and benzene that takes place with 100 °C lower temperature than the standard reaction (Pt-on-SiO2). We observe a pore size effect in the nMOF series where the small pore of Pt⊂nMOF-801 does not produce the same products, while the larger pore Pt⊂nUiO-67 catalyst provides the same products but with different selectivity. The (Pt⊂nMOF)nanocrystal spent catalyst is found to maintain the original crystallinity, and be recyclable without any byproduct residues.
Co-reporter:Alejandro M. Fracaroli ; Hiroyasu Furukawa ; Mitsuharu Suzuki ; Matthew Dodd ; Satoshi Okajima ; Felipe Gándara ; Jeffrey A. Reimer
Journal of the American Chemical Society 2014 Volume 136(Issue 25) pp:8863-8866
Publication Date(Web):June 9, 2014
DOI:10.1021/ja503296c
The selective capture of carbon dioxide in the presence of water is an outstanding challenge. Here, we show that the interior of IRMOF-74-III can be covalently functionalized with primary amine (IRMOF-74-III-CH2NH2) and used for the selective capture of CO2 in 65% relative humidity. This study encompasses the synthesis, structural characterization, gas adsorption, and CO2 capture properties of variously functionalized IRMOF-74-III compounds (IRMOF-74-III-CH3, -NH2, -CH2NHBoc, -CH2NMeBoc, -CH2NH2, and -CH2NHMe). Cross-polarization magic angle spinning 13C NMR spectra showed that CO2 binds chemically to IRMOF-74-III-CH2NH2 and -CH2NHMe to make carbamic species. Carbon dioxide isotherms and breakthrough experiments show that IRMOF-74-III-CH2NH2 is especially efficient at taking up CO2 (3.2 mmol of CO2 per gram at 800 Torr) and, more significantly, removing CO2 from wet nitrogen gas streams with breakthrough time of 610 ± 10 s g–1 and full preservation of the IRMOF structure.
Co-reporter:Juncong Jiang ; Felipe Gándara ; Yue-Biao Zhang ; Kyungsu Na ; Omar M. Yaghi ;Walter G. Klemperer
Journal of the American Chemical Society 2014 Volume 136(Issue 37) pp:12844-12847
Publication Date(Web):August 26, 2014
DOI:10.1021/ja507119n
Superacids, defined as acids with a Hammett acidity function H0 ≤ −12, are useful materials, but a need exists for new, designable solid state systems. Here, we report superacidity in a sulfated metal–organic framework (MOF) obtained by treating the microcrystalline form of MOF-808 [MOF-808-P: Zr6O5(OH)3(BTC)2(HCOO)5(H2O)2, BTC = 1,3,5-benzenetricarboxylate] with aqueous sulfuric acid to generate its sulfated analogue, MOF-808-2.5SO4 [Zr6O5(OH)3(BTC)2(SO4)2.5(H2O)2.5]. This material has a Hammett acidity function H0 ≤ −14.5 and is thus identified as a superacid, providing the first evidence for superacidity in MOFs. The superacidity is attributed to the presence of zirconium-bound sulfate groups structurally characterized using single-crystal X-ray diffraction analysis.
Co-reporter:Felipe Gándara ; Hiroyasu Furukawa ; Seungkyu Lee
Journal of the American Chemical Society 2014 Volume 136(Issue 14) pp:5271-5274
Publication Date(Web):March 21, 2014
DOI:10.1021/ja501606h
The use of porous materials to store natural gas in vehicles requires large amounts of methane per unit of volume. Here we report the synthesis, crystal structure and methane adsorption properties of two new aluminum metal–organic frameworks, MOF-519 and MOF-520. Both materials exhibit permanent porosity and high methane volumetric storage capacity: MOF-519 has a volumetric capacity of 200 and 279 cm3 cm–3 at 298 K and 35 and 80 bar, respectively, and MOF-520 has a volumetric capacity of 162 and 231 cm3 cm–3 under the same conditions. Furthermore, MOF-519 exhibits an exceptional working capacity, being able to deliver a large amount of methane at pressures between 5 and 35 bar, 151 cm3 cm–3, and between 5 and 80 bar, 230 cm3 cm–3.
Metal–organic frameworks (MOFs) containing more than two kinds of metal ions mixed in one secondary building unit are rare because the synthesis often yields mixed MOF phases rather than a pure phase of a mixed-metal MOF (MM-MOF). In this study, we use a one-pot reaction to make microcrystalline MOF-74 [M2(DOT); DOT = dioxidoterephthalate] with 2 (Mg and Co), 4 (Mg, Co, Ni, and Zn), 6 (Mg, Sr, Mn, Co, Ni, and Zn), 8 (Mg, Ca, Sr, Mn, Fe, Co, Ni, and Zn), and 10 (Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Zn, and Cd) different kinds of divalent metals. The powder X-ray diffraction patterns of MM-MOF-74 were identical with those of single-metal MOF-74, and no amorphous phases were found by scanning electron microscopy. The successful preparation of guest-free MM-MOF-74 samples was confirmed by N2 adsorption measurements. Elemental analysis data also support the fact that all metal ions used in the MOF synthesis are incorporated within the same MOF-74 structure. Energy-dispersive X-ray spectroscopies indicate that metal ions are heterogeneously distributed within each of the crystalline particles. This approach is also employed to incorporate metal ions (i.e., Ca, Sr, Ba, and Cd) from which the parent MOF structure could not be made as a single-metal-containing MOF.
Co-reporter:Dan Li;Hiroyasu Furukawa;Hexiang Deng;Cong Liu;David S. Eisenberg;
Proceedings of the National Academy of Sciences 2014 111(1) pp:191-196
Publication Date(Web):December 23, 2013
DOI:10.1073/pnas.1321797111
New materials capable of binding carbon dioxide are essential for addressing climate change. Here, we demonstrate that amyloids,
self-assembling protein fibers, are effective for selective carbon dioxide capture. Solid-state NMR proves that amyloid fibers
containing alkylamine groups reversibly bind carbon dioxide via carbamate formation. Thermodynamic and kinetic capture-and-release
tests show the carbamate formation rate is fast enough to capture carbon dioxide by dynamic separation, undiminished by the
presence of water, in both a natural amyloid and designed amyloids having increased carbon dioxide capacity. Heating to 100
°C regenerates the material. These results demonstrate the potential of amyloid fibers for environmental carbon dioxide capture.
Hydrophobic zeolitic imidazolate frameworks (ZIFs) with the chabazite (CHA) topology are synthesized by incorporating two distinct imidazolate links. Zn(2-mIm)0.86(bbIm)1.14 (ZIF-300), Zn(2-mIm)0.94(cbIm)1.06 (ZIF-301), and Zn(2-mIm)0.67(mbIm)1.33 (ZIF-302), where 2-mIm=2-methylimidazolate, bbIm=5(6)-bromobenzimidazolate, cbIm=5(6)-chlorobenzimidazolate, and mbIm=5(6)-methylbenzimidazolate, were prepared by reacting zinc nitrate tetrahydrate and 2-mIm with the respective bIm link in a mixture of N,N-dimethylformamide (DMF) and water. Their structures were determined by single-crystal X-ray diffraction and their permanent porosity shown. All of these structures are hydrophobic as confirmed by water adsorption isotherms. All three ZIFs are equally effective at the dynamic separation of CO2 from N2 under both dry and humid conditions without any loss of performance over three cycles and can be regenerated simply by using a N2 flow at ambient temperature.
Co-reporter:Kyung Min Choi, Hyung Mo Jeong, Jung Hyo Park, Yue-Biao Zhang, Jeung Ku Kang, and Omar M. Yaghi
ACS Nano 2014 Volume 8(Issue 7) pp:7451
Publication Date(Web):July 7, 2014
DOI:10.1021/nn5027092
The high porosity of metal–organic frameworks (MOFs) has been used to achieve exceptional gas adsorptive properties but as yet remains largely unexplored for electrochemical energy storage devices. This study shows that MOFs made as nanocrystals (nMOFs) can be doped with graphene and successfully incorporated into devices to function as supercapacitors. A series of 23 different nMOFs with multiple organic functionalities and metal ions, differing pore sizes and shapes, discrete and infinite metal oxide backbones, large and small nanocrystals, and a variety of structure types have been prepared and examined. Several members of this series give high capacitance; in particular, a zirconium MOF exhibits exceptionally high capacitance. It has the stack and areal capacitance of 0.64 and 5.09 mF cm–2, about 6 times that of the supercapacitors made from the benchmark commercial activated carbon materials and a performance that is preserved over at least 10000 charge/discharge cycles.Keywords: electrochemical capacitors; metal−organic frameworks; nanocrystals of MOFs
Co-reporter:Nhung T. T. Nguyen;Dr. Hiroyasu Furukawa;Dr. Felipe Gándara;Dr. Hoang T. Nguyen;Kyle E. Cordova; Omar M. Yaghi
Angewandte Chemie International Edition 2014 Volume 53( Issue 40) pp:10645-10648
Publication Date(Web):
DOI:10.1002/anie.201403980
Abstract
Hydrophobic zeolitic imidazolate frameworks (ZIFs) with the chabazite (CHA) topology are synthesized by incorporating two distinct imidazolate links. Zn(2-mIm)0.86(bbIm)1.14 (ZIF-300), Zn(2-mIm)0.94(cbIm)1.06 (ZIF-301), and Zn(2-mIm)0.67(mbIm)1.33 (ZIF-302), where 2-mIm=2-methylimidazolate, bbIm=5(6)-bromobenzimidazolate, cbIm=5(6)-chlorobenzimidazolate, and mbIm=5(6)-methylbenzimidazolate, were prepared by reacting zinc nitrate tetrahydrate and 2-mIm with the respective bIm link in a mixture of N,N-dimethylformamide (DMF) and water. Their structures were determined by single-crystal X-ray diffraction and their permanent porosity shown. All of these structures are hydrophobic as confirmed by water adsorption isotherms. All three ZIFs are equally effective at the dynamic separation of CO2 from N2 under both dry and humid conditions without any loss of performance over three cycles and can be regenerated simply by using a N2 flow at ambient temperature.
Co-reporter:Yue-Biao Zhang ; Jie Su ; Hiroyasu Furukawa ; Yifeng Yun ; Felipe Gándara ; Adam Duong ; Xiaodong Zou
Journal of the American Chemical Society 2013 Volume 135(Issue 44) pp:16336-16339
Publication Date(Web):October 21, 2013
DOI:10.1021/ja409033p
The crystal structure of a new covalent organic framework, termed COF-320, is determined by single-crystal 3D electron diffraction using the rotation electron diffraction (RED) method for data collection. The COF crystals are prepared by an imine condensation of tetra-(4-anilyl)methane and 4,4′-biphenyldialdehyde in 1,4-dioxane at 120 °C to produce a highly porous 9-fold interwoven diamond net. COF-320 exhibits permanent porosity with a Langmuir surface area of 2400 m2/g and a methane total uptake of 15.0 wt % (176 cm3/cm3) at 25 °C and 80 bar. The successful determination of the structure of COF-320 directly from single-crystal samples is an important advance in the development of COF chemistry.
Co-reporter:Xueqian Kong;Hexiang Deng;Fangyong Yan;Jihan Kim;Joseph A. Swisher;Berend Smit;Jeffrey A. Reimer
Science 2013 Volume 341(Issue 6148) pp:882-885
Publication Date(Web):23 Aug 2013
DOI:10.1126/science.1238339
Mapping Molecular Linkers
In metal-organic framework compounds, inorganic centers (metal atoms or clusters) are linked by bidentate organic groups. Normally, the same group is used throughout the structure, but recently, synthesis with linkers bearing different functional groups has produced well-defined materials. Kong et al. (p. 882, published online 25 July) combined solid-state nuclear magnetic resonance and molecular simulations to map the distributions of linkers in these materials as random, well-mixed, or clustered.
Co-reporter:Hiroyasu Furukawa;Kyle E. Cordova;Michael O’Keeffe
Science 2013 Volume 341(Issue 6149) pp:
Publication Date(Web):30 Aug 2013
DOI:10.1126/science.1230444
Structured Abstract
Background
Metal-organic frameworks (MOFs) are made by linking inorganic and organic units by strong bonds (reticular synthesis). The flexibility with which the constituents’ geometry, size, and functionality can be varied has led to more than 20,000 different MOFs being reported and studied within the past decade. The organic units are ditopic or polytopic organic carboxylates (and other similar negatively charged molecules), which, when linked to metal-containing units, yield architecturally robust crystalline MOF structures with a typical porosity of greater than 50% of the MOF crystal volume. The surface area values of such MOFs typically range from 1000 to 10,000 m2/g, thus exceeding those of traditional porous materials such as zeolites and carbons. To date, MOFs with permanent porosity are more extensive in their variety and multiplicity than any other class of porous materials. These aspects have made MOFs ideal candidates for storage of fuels (hydrogen and methane), capture of carbon dioxide, and catalysis applications, to mention a few.
Metal-organic framework (MOF) structures are amenable to expansion and incorporation of multiple functional groups within their interiors. (A) The isoreticular expansion of MOFs maintains the network’s topology by using an expanded version of the parent organic linker. Examples of catalysis in MOFs are shown in the large space created by IRMOF-74-XI; Me is a methyl group. (B) Conceptual illustration of a multivariate MOF (MTV-MOF) whose pores are decorated by heterogeneous mixtures of functionalities that arrange in specific sequences. (Background) Optical image of zeolitic imidazolate framework (ZIF) crystals.
Advances
The ability to vary the size and nature of MOF structures without changing their underlying topology gave rise to the isoreticular principle and its application in making MOFs with the largest pore aperture (98 Å) and lowest density (0.13 g/cm3). This has allowed for the selective inclusion of large molecules (e.g., vitamin B12) and proteins (e.g., green fluorescent protein) and the exploitation of the pores as reaction vessels. Along these lines, the thermal and chemical stability of many MOFs has made them amenable to postsynthetic covalent organic and metal-complex functionalization. These capabilities enable substantial enhancement of gas storage in MOFs and have led to their extensive study in the catalysis of organic reactions, activation of small molecules (hydrogen, methane, and water), gas separation, biomedical imaging, and proton, electron, and ion conduction. At present, methods are being developed for making nanocrystals and supercrystals of MOFs for their incorporation into devices.
Outlook
The precise control over the assembly of MOFs is expected to propel this field further into new realms of synthetic chemistry in which far more sophisticated materials may be accessed. For example, materials can be envisaged as having (i) compartments linked together to operate separately, yet function synergistically; (ii) dexterity to carry out parallel operations; (iii) ability to count, sort, and code information; and (iv) capability of dynamics with high fidelity. Efforts in this direction are already being undertaken through the introduction of a large number of different functional groups within the pores of MOFs. This yields multivariate frameworks in which the varying arrangement of functionalities gives rise to materials that offer a synergistic combination of properties. Future work will involve the assembly of chemical structures from many different types of building unit, such that the structures’ function is dictated by the heterogeneity of the specific arrangement of their constituents.
Co-reporter:William Morris, Boris Volosskiy, Selcuk Demir, Felipe Gándara, Psaras L. McGrier, Hiroyasu Furukawa, Duilio Cascio, J. Fraser Stoddart, and Omar M. Yaghi
Three new metal–organic frameworks [MOF-525, Zr6O4(OH)4(TCPP-H2)3; MOF-535, Zr6O4(OH)4(XF)3; MOF-545, Zr6O8(H2O)8(TCPP-H2)2, where porphyrin H4-TCPP-H2 = (C48H24O8N4) and cruciform H4-XF = (C42O8H22)] based on two new topologies, ftw and csq, have been synthesized and structurally characterized. MOF-525 and -535 are composed of Zr6O4(OH)4 cuboctahedral units linked by either porphyrin (MOF-525) or cruciform (MOF-535). Another zirconium-containing unit, Zr6O8(H2O)8, is linked by porphyrin to give the MOF-545 structure. The structure of MOF-525 was obtained by analysis of powder X-ray diffraction data. The structures of MOF-535 and -545 were resolved from synchrotron single-crystal data. MOF-525, -535, and -545 have Brunauer–Emmett–Teller surface areas of 2620, 1120, and 2260 m2/g, respectively. In addition to their large surface areas, both porphyrin-containing MOFs are exceptionally chemically stable, maintaining their structures under aqueous and organic conditions. MOF-525 and -545 were metalated with iron(III) and copper(II) to yield the metalated analogues without losing their high surface area and chemical stability.
Co-reporter:Dr. Felipe Gándara;Dr. Ferno J. Uribe-Romo;Dr. David K. Britt;Dr. Hiroyasu Furukawa;Dr. Liao Lei;Rui Cheng; Xiangfeng Duan; Michael O'Keeffe; Omar M. Yaghi
Chemistry - A European Journal 2012 Volume 18( Issue 34) pp:10595-10601
Publication Date(Web):
DOI:10.1002/chem.201103433
Abstract
A new family of porous crystals was prepared by combining 1H-1,2,3-triazole and divalent metal ions (Mg, Mn, Fe, Co, Cu, and Zn) to give six isostructural metal-triazolates (termed MET-1 to 6). These materials are prepared as microcrystalline powders, which give intense X-ray diffraction lines. Without previous knowledge of the expected structure, it was possible to apply the newly developed charge-flipping method to solve the complex crystal structure of METs: all the metal ions are octahedrally coordinated to the nitrogen atoms of triazolate such that five metal centers are joined through bridging triazolate ions to form super-tetrahedral units that lie at the vertexes of a diamond-type structure. The variation in the size of metal ions across the series provides for precise control of pore apertures to a fraction of an Angstrom in the range 4.5 to 6.1 Å. MET frameworks have permanent porosity and display surface areas as high as some of the most porous zeolites, with one member of this family, MET-3, exhibiting significant electrical conductivity.
Co-reporter:Hiroyasu Furukawa ; Felipe Gándara ; Yue-Biao Zhang ; Juncong Jiang ; Wendy L. Queen ; Matthew R. Hudson □
Journal of the American Chemical Society () pp:
Publication Date(Web):March 3, 2014
DOI:10.1021/ja500330a
Water adsorption in porous materials is important for many applications such as dehumidification, thermal batteries, and delivery of drinking water in remote areas. In this study, we have identified three criteria for achieving high performing porous materials for water adsorption. These criteria deal with condensation pressure of water in the pores, uptake capacity, and recyclability and water stability of the material. In search of an excellently performing porous material, we have studied and compared the water adsorption properties of 23 materials, 20 of which are metal–organic frameworks (MOFs). Among the MOFs are 10 zirconium(IV) MOFs with a subset of these, MOF-801-SC (single crystal form), −802, −805, −806, −808, −812, and −841 reported for the first time. MOF-801-P (microcrystalline powder form) was reported earlier and studied here for its water adsorption properties. MOF-812 was only made and structurally characterized but not examined for water adsorption because it is a byproduct of MOF-841 synthesis. All the new zirconium MOFs are made from the Zr6O4(OH)4(−CO2)n secondary building units (n = 6, 8, 10, or 12) and variously shaped carboxyl organic linkers to make extended porous frameworks. The permanent porosity of all 23 materials was confirmed and their water adsorption measured to reveal that MOF-801-P and MOF-841 are the highest performers based on the three criteria stated above; they are water stable, do not lose capacity after five adsorption/desorption cycles, and are easily regenerated at room temperature. An X-ray single-crystal study and a powder neutron diffraction study reveal the position of the water adsorption sites in MOF-801 and highlight the importance of the intermolecular interaction between adsorbed water molecules within the pores.
Co-reporter:Dani Peri ; Jim Ciston ; Felipe Gándara ; Yingbo Zhao
Inorganic Chemistry () pp:
Publication Date(Web):November 20, 2013
DOI:10.1021/ic402435z
Despite remarkable progress in the field of MOFs, structures based on long-flexible organic linkers are scarce and the majority of such materials rely on rigid linkers. In this work, crystals of a new metal–organic double ladder (MODL) are obtained by linking a pentapeptide (NH2-Glu-pCO2Phe-pCO2Phe-Ala-Gly-OH) with cadmium acetate to produce a Cd(2-pyrrolidone-pCO2Phe-pCO2Phe-Ala-Gly)(H2O)3 framework. SEM and TEM analyses show the fibrous nature of the crystals and show that the infinite cadmium oxide rod secondary building units (SBUs) are aligned with the longitudinal axis of the nanofibers.
Reticular chemistry, linking molecular building blocks together by strong bonds to make porous frameworks, is a rapidly expanding field of research, engaging laboratories worldwide. However, as with any emerging field, there exist ‘folklores’ permeating through the scientific discourse. These folklores do little in the way of advancing the field and, in no uncertain terms, negatively color our scientific pursuits. It is within this context that we seek to bring the folklores out into the open to provide the true realities of reticular chemistry.
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