Magnetic Fe3O4 nanospheres coated with Mg-MOF-74 have been facilely prepared via epitaxial growth. Owing to the intrinsic hydrophilic pore surface and size-exclusive properties of Mg-MOF-74, the Fe3O4@Mg-MOF-74 core–shell nanoparticles show effective and selective enrichment of 441 N-glycosylation sites of 418 glycopeptides from 125 glycoproteins in 1 μL of human serum.

•A novel imidazole-phosphonic acid was firstly used to synthesize MOFs.•The synthesized MOF has remarkable thermal and chemical stabilities.•The synthesized MOF showed high selectivity and sensitivity for sensing Cu2 + ions.A phosphonic acid, 4-(1H-imidazole-4-yl)phenylphosphonic acid (H3piz) was firstly synthesized and used as a ligand to construct a metal phosphonate, [(ZnHpiz)]n (ZnPIF-1). The structure of ZnPIF-1 features as “inorganic” zinc phosphate chains, which are linked with the neighboring ones by Hpiz2 − into a two-dimensional (2-D) layered structure. Study of thermal and chemical stability of ZnPIF-1 demonstrated its high thermal stability and remarkable chemical resistance to boiling water and acid/alkaline condition. Furthermore, luminescence studies revealed that ZnPIF-1 showed high selectivity and sensitivity for sensing Cu2 + ions over other metal ions.A phosphonic acid, 4-(1H-imidazole-4-yl)phenylphosphonic acid (H3piz) was firstly synthesized and used as a ligand to construct a metal phosphonate, [(ZnHpiz)]n (ZnPIF-1), which shows high selectivity and sensitivity for sensing Cu2 + ions over other metal ions.Download high-res image (392KB)Download full-size image

A 7-connected Zn4O unit has been theoretically predicted based on the model of basic zinc acetate [Zn4O(CH3COO)6], which was then experimentally extended into a three-dimensional structure featuring three kinds of nanocage in a unit cell.

An indium phosphonocarboxylate framework, {H3O[In(pbpdc)]·3H2O}n (InPCF-1) (pbpdc = 4′-phosphonobiphenyl-3,5-dicarboxylate), was hydrothermally synthesized. The structure of InPCF-1 features the inorganic chains as rod-shaped second building units. The rod-packing arrangement results in a three-dimensional (3-D) framework with a novel (3,4,5)-connected net. Studies of the gas adsorption, and thermal and chemical stability of InPCF-1 demonstrated its adsorption capacity for CO2, selective separation of CO2 over O2 and N2, high thermal stability, and a remarkable chemical resistance to boiling water, ethyl alcohol, and methylbenzene. Importantly, InPCF-1 shows a selective and sensitive response to Cu2+ ions. It also serves as a sensor for methylviologen.

Using structure-directing agents, pore space partitions of a Zn-phosphonocarboxylate framework have been achieved. Selective adsorption of CO2 over N2 has been greatly improved from ca. 9:1 to 94:1.

A three-dimensional porous structure of [Zn7O2(bpdc)4(dmpp)2]·6DEF·10H2O (MAC-7, H2bpdc = 4,4′-biphenyldicarboxylic acid, Hdmpp = 3,5-dimethyl-4-(4′-pyridyl)pyrazole), built of 12-bridged carboxylate-pyrazolate shared Zn7O2 clusters, has been synthesized. Because of the presence of 12-bridged carboxylate-pyrazolate shared building block, MAC-7 is a double-linked pcu-type framework and shows reversible phase transformation. Photoluminescent property studies indicate that MAC-7 could sense nitrobenzene over toluene, p-xylene, and mesitylene by luminescent quenching.

A 2D phosphonate MOF {[Ni(Hptz)2]·7H2O}n (H2ptz = 4-(1,2,4-triazol-4-yl)phenylphosphonic acid) (2) is obtained through crystal transformation from a trinuclear compound [Ni3(Hptz)6·(H2O)6]·9H2O (1). Studies of chemical stability show that 2 retains its crystallinity in boiling water and organic solvents. 2 also exhibits high adsorption capacity for CO2 (80 cm3(STP) g−1) and selective separation of CO2 over N2.

A three-dimensional (3D) porous structure of [Cu3(μ3-OH)(μ2-O)(dmtrz)2(HCOO)(μ2-H2O)(H2O)3]·H2O (1) has been in situ solvothermally synthesized. In 1, the trinuclear triangular [Cu3(μ3-OH)(μ2-O)(dmtrz)2] cluster connects itself infinitely, resulting in the type-II channel structure, which is different from that of the rigid type-I channel structure reported previously. Reversible dehydration and rehydration induced crystal-to-amorphous-like phase transformation for structure 1 has been observed and confirmed by PXRD patterns and gas adsorption. Furthermore, as a response to the structural transformation, the stimuli-induced modulation of magnetic properties have been observed.

Solvothermal reaction of [1,1′-biphenyl]-3,3′,5,5′-tetracarboxylic acid (H4bptc), 3,5-diamine-1H-1,2,4-triazole (Hdatrz) and zinc acetate affords a three-dimensional structure of [Zn2(bptc)(datrz)](CH3)2NH2·2H2O (MAC-6). It is a (3,6)-connected framework built of paddle-wheel and triazolate-dinuclear metal clusters together with bptc ligands, and shows a novel (42.6)2(44.66.85) topology. Heating crystal samples of MAC-6 leads to the structure transformation to [Zn2(bptc)(datrz)(H2O)0.5](CH3)2NH2·H2O (MAC-6′), in which the paddle-wheel unit deforms to a dinuclear unit. Remarkably, MAC-6′ can reversibly recover to MAC-6 when the samples of MAC-6′ were immersed into DMF. The deformation and reformation of the paddle-wheel unit were studied by single-crystal-to-single-crystal (SCSC) transformation. In addition, their photoluminescent properties were also studied.

Cyanide group is a robust electron-mediate ligand, widely used in functional coordination polymers. Synthesis of cyanide-containing functional coordination polymersvia solvothermal in situ reaction is a new efficient approach. In this paper, four novel ternary coordination polymers, namely [Ag3(trz)2(CN)]n (1), [Ag3(detrz)2(CN)]n (2), [Ag4(dptrz)2(CN)2]n (3), [Ag3(dptrz)2(CN)]n (4) (Htrz = 1H-1,2,4-triazole, Hdetrz = 3,5-diethyl-1H-1,2,4-triazole, Hdptrz = 3,5-dipropyl-1H-1,2,4-triazole), were solvothermally synthesized and characterized. The cyanide groups are all in situ generated from C–C cleavage reaction of acetonitrile. The cyanide group acts as terminal group in 1, while as linker in 2, 3, 4. Phosphorescent properties of these in situ products are studied and compared with binary silver-triazole coordination polymers. The results show that phosphorescent emissions of 2, 3, and 4 are red-shifted compared to that of 1.

Two novel Zn(II) metal–organic frameworks (MOFs) constructed by trinuclear-triangular and paddle-wheel units, namely {[Zn5(dmtrz)3(IPA)3(OH)]·DMF·H2O}n (MAC-4, Hdmtrz = 3,5-dimethyl-1H-1,2,4-triazole, H2IPA = isophthalic acid, DMF = dimethyl formamide) and {[Zn5(dmtrz)3(OH-IPA)3(OH)]·DMF·5H2O}n (MAC-4-OH, OH-H2IPA = 5-hydroxyisophthalic acid), were solvothermally synthesized. Single-crystal analyses reveal that MAC-4-OH is an iso-reticular framework of MAC-4 with channels functionalized by hydroxyl groups. Gas adsorption reveals that MAC-4-OH shows a significant enhancement for CO2 uptake compared with that of MAC-4 due to the existence of electrostatic attractive interactions, though its surface area is lower than that of MAC-4.

Two novel zinc phosphonocarboxylates, Zn3(pbc)2(bpy)(H2O)·H2O (1) and Zn2(pbc)2·Zn(bpy)(H2O)4·2H2O (2) (pbc = 4-phosphono-benzoic acid, bpy = 2,2′-bipyridine), were hydrothermally synthesized and structurally characterized. Both of them exhibit zeolitic ABW topology in which double-zigzag inorganic chains are cross-linked by the organic parts. It is notable that the metal complex Zn(bpy)(H2O)x plays different roles in the two compounds. In 1, the Zn(bpy)(H2O) units coordinate with the phosphonate and carboxylate oxygen atoms and participate in the construction of the three-dimensional framework. In 2, the in situ generated [Zn(bpy)(H2O)4]2+ cation acts as a template, which directs the ABW-type open-framework by strong hydrogen bonds. It is the first example where a metal complex is used as a template in the synthesis of metal phosphonates. The luminescent properties of 1 and 2 are also investigated.

A three-dimensional (3D) metal–organic framework {[Zn2(HBDC)2(dmtrz)2]·guest}n with pcu net has been solvothermally synthesized, which shows selective adsorption of linear and monobranched hexane isomers over a dibranched one.

Two novel porous metal–organic frameworks {Zn7(btc)4(dmtrz)2(H2O)5}n (1) and {[Zn6(btc)4(dmtrz)3]·3H3O·2H2O}n (2) (H3btc = 1,3,5-benzenetricarboxylic acid, Hdmtrz = 3,5-dimethyl-1H-1,2,4-triazole) have been solvothermally synthesized. Single-crystal structure analysis reveals that both structure 1 and 2 contain special triazole-carboxylate shared paddle-wheel units. The crucial factors to the assembly of such paddle-wheel units are discussed. Gas adsorption studies suggest that 2 is a potential microporous material for adsorptive separation of CO2 over N2.

A novel three-dimensional (3D) [Ag3(dmtrz)2(CN)]n (1) with a three-fold interpenetrated CdSO4-type net is in situ solvothermal synthesized, and influential factors in the in situ reaction are briefly discussed. The luminescent property studies reveal that 1 shows green phosphorescent emission upon excitation while other binary silver(I)-dmtrz compounds discussed in this paper only emit blue phosphorescence.

Two zinc phosphonocarboxylate frameworks, Zn1.5(pbc)(2,2′-bpy) (1) (2,2′-bpy = 2,2′-bipyridine) and Zn(pbc)(NH2(CH3)2)0.5·0.5H3O (2), were synthesized in a mixed-solvothermal condition. Their structures have been determined by single-crystal X-ray diffraction analysis, IR spectra and thermogravimetric analysis. Compound 1 is a three-dimensional zinc phosphonocarboxylate with auxiliary ligand of 2,2′-bpy. 2 was obtained by reheating the filtrate of 1 and shows a nanoporous open-framework with zeolitic GIS topology. At room temperature, 2 can absorb organic amine and solvents in its channels, causing a breathing effect and shrinkage of the pores, resulting in single-crystal-to-single-crystal transformation to structure 2a, Zn(pbc)(NH2(CH3)2)·0.5DMF·2H2O. The porosity of 2 was demonstrated by the methanol and water adsorption experiments, indicating selective guest uptake.

The layered-solvothermal synthesis of zinc acetate dihydrate with 5-phosphonobenzene-1,3-dicarboxylic acid yields a three-dimensional rutile-type porous metal–organic framework, which is an anionic open-framework containing local proton transfer with hydrated protons and showing excellent size-selective properties.

Three porous metal−organic frameworks have been constructed from the new developed C3-symmetric hexacarboxylic acid 3,3′,3′′,5,5′,5′′-benzene-1,3,5-triyl-hexabenzoic acid (H6BHB) of different NaCl- and Al2O3-type topologies. The activated metal−organic frameworks (MOFs) exhibit permanent porosities as revealed in their gas and vapor adsorption isotherms, highlighting the promise of this new ligand for the construction of porous MOFs for gas storage and separation.

To systematically explore the assembly mechanism of a rutile-type open framework of {[Zn3(pbdc)2]·2H3O}n (3) (H4pbdc = 5-phosphonobenzene-1,3-dicarboxylic acid) constructed by 3-connected pbdc ligands and 6-connected Zn3(CO2)4(PO3)2 secondary building units (Zn3-SBUs), three major factors including solvothermal procedures, types of solvents and amines, are taken into consideration. Seven novel structures, namely {[Zn5(pbdc)2(OH)2(H2O)4]·4H2O}n (1), {[Zn3(pbdc)2·H2O]·(Htea)·H3O·2–5(H2O)}n (2), {[Zn3(pbdc)2](H3O)2(dma)}n (4), {[Zn2(pbdc)(taea)]·3H2O}n (5), {[Zn3(pbdc)2(Hpda)2]·2H2O}n (6), {[Zn5(pbdc)2(Hpbdc)2]·2H2pz·9H2O}n (7), {[Zn3(pbdc)2]·Hpd·H3O·4H2O}n (8) are obtained. The results indicate that the layered-solvothermal method and the isopropanol solvent play crucial roles in the construction of the special anionic open framework of [Zn3(pbdc)2]2−. Changing these two factors led molecular assembly away from the rutile-type open framework. However, amines play a variable role in the framework, which means that by using appropriate amines, molecular assembly could generate the open framework of [Zn3(pbdc)2]2− with pores decorated by amines. These results suggest a different approach towards decorating pores in anionic frameworks with precise structural information.

Two novel metal−organic frameworks (MOFs), Cu(3,4′-bpdc)(H2O)·DMF·2H2O (1) and Cu(3,4′-bpdc)(H2O)·2DMF·4.5H2O (2), have been solvothermally synthesized by the reaction of a unsymmetrically substituted carboxylate ligand 3,4′-biphenyldicarboxylic acid (3,4′-bpdc) and Cu(NO3)2·2.5H2O. X-ray crystal structural analyses reveal that both MOFs possess the binuclear paddle-wheel units [Cu2(O2CR)4], which are linked by the biphenyl connectors, to give two different three-dimensional (3-D) frameworks. The structural diversities are due to the different coordinated arrangements of the two distinct carboxylate groups. In 1, the noncentral symmetrical A−A−B−B arrangement leads to an uncommon twisted Cu-paddlewheel unit, which favors a tetrahedral configuration to generate a 3-fold interpenetrating 3-D framework with a diamond topology. In 2, the paddle-wheel unit constructed by the central symmetrical A−B−A−B arrangement of the ligand acts as a square-planar 4-connected node to give a 2-fold interpenetrating 3-D framework with an NbO topology. These two polymorphs are very rare in MOFs that exhibit similar metal local coordination geometry and the same secondary building units (SBU) but different ligands linking modes. Furthermore, both 1 and 2 possess large one-dimensional channels and show the ability to adsorb H2.

Four metal phosphonate hybrid compounds, [Pb(Hpbc)] (1), [Pb3(pbc)2(H2O)2] (2), [Cd(H2pbc)2(H2O)2] (3) and [Cd1.5(pbc)(H2O)1.5] · 0.5H2O (4) (H3pbc = 3-phosphono-benzoic acid) were successfully synthesized by the hydrothermal/solvothermal reaction of metal acetate and 3-phosphono-benzoic acid. Compounds 1–4 were pH-dependent products and characterized by elemental analysis, Fourier transform infrared (FT-IR) spectra and single-crystal X-ray diffraction studies. Compound 1 is a two-dimensional (2D) structure constructed by inorganic layer and organic pendant. With the increase of pH value, structure 2 shows 3D inorganic framework with distributing organic moieties in the channels. In 3, the Cd2O10 dimers are linked by alternating terminal and bridging ligands, resulting in 1D chain structure. Compound 4 is a 2D structure where the 1D inorganic chains are connected by the organic moieties of the ligands.The reaction of 3-phosphono-benzoic acid and lead/cadmium salt with different pH value lead to four novel metal phosphonates. Their structures range from one dimension to three dimension, showing structural response on pH value of the reaction clearly.

Three homochiral metal–organic frameworks (MOFs) based on enantiopure chiral ligand: (R)-2,2’-dimethoxy-5,5′,6,6′,7,7′,8,8′-octahydro-1,1′-binaphthyl-3,3′-dicarboxylic acid (H2L), namely Cd(L)(Py)31, Cu(L)(Py)32, Na[Cd(L)(LH)] · 2.5H2O 3 (Py = pyridine), were firstly synthesized, under solvothermal reactions. X-ray single-crystal diffraction studies reveal that 1 and 2 adopt one-dimensional (1D) infinite helical structures, while 3 possesses 2D chiral framework structure adopting ABAB offset stacking modes along the a-axis. Thermogravimetric analyses (TGA) display that 3 is thermally stable to 330 °C which is rare for homochiral MOFs.Three homochiral metal–organic frameworks are obtained using enantiopure octahydrobinaphthyl-derived dicarboxylic acid as bridging ligands and transition metal ions. Two polymeric motifs were observed in these compounds: the one-dimensional infinite chiral helical structure and the two-dimensional rhombic grids network.

Magnetic Fe3O4 nanospheres coated with Mg-MOF-74 have been facilely prepared via epitaxial growth. Owing to the intrinsic hydrophilic pore surface and size-exclusive properties of Mg-MOF-74, the Fe3O4@Mg-MOF-74 core–shell nanoparticles show effective and selective enrichment of 441 N-glycosylation sites of 418 glycopeptides from 125 glycoproteins in 1 μL of human serum.

Using structure-directing agents, pore space partitions of a Zn-phosphonocarboxylate framework have been achieved. Selective adsorption of CO2 over N2 has been greatly improved from ca. 9:1 to 94:1.

A three-dimensional (3D) metal–organic framework {[Zn2(HBDC)2(dmtrz)2]·guest}n with pcu net has been solvothermally synthesized, which shows selective adsorption of linear and monobranched hexane isomers over a dibranched one.

The layered-solvothermal synthesis of zinc acetate dihydrate with 5-phosphonobenzene-1,3-dicarboxylic acid yields a three-dimensional rutile-type porous metal–organic framework, which is an anionic open-framework containing local proton transfer with hydrated protons and showing excellent size-selective properties.

An indium phosphonocarboxylate framework, {H3O[In(pbpdc)]·3H2O}n (InPCF-1) (pbpdc = 4′-phosphonobiphenyl-3,5-dicarboxylate), was hydrothermally synthesized. The structure of InPCF-1 features the inorganic chains as rod-shaped second building units. The rod-packing arrangement results in a three-dimensional (3-D) framework with a novel (3,4,5)-connected net. Studies of the gas adsorption, and thermal and chemical stability of InPCF-1 demonstrated its adsorption capacity for CO2, selective separation of CO2 over O2 and N2, high thermal stability, and a remarkable chemical resistance to boiling water, ethyl alcohol, and methylbenzene. Importantly, InPCF-1 shows a selective and sensitive response to Cu2+ ions. It also serves as a sensor for methylviologen.

Two novel Zn(II) metal–organic frameworks (MOFs) constructed by trinuclear-triangular and paddle-wheel units, namely {[Zn5(dmtrz)3(IPA)3(OH)]·DMF·H2O}n (MAC-4, Hdmtrz = 3,5-dimethyl-1H-1,2,4-triazole, H2IPA = isophthalic acid, DMF = dimethyl formamide) and {[Zn5(dmtrz)3(OH-IPA)3(OH)]·DMF·5H2O}n (MAC-4-OH, OH-H2IPA = 5-hydroxyisophthalic acid), were solvothermally synthesized. Single-crystal analyses reveal that MAC-4-OH is an iso-reticular framework of MAC-4 with channels functionalized by hydroxyl groups. Gas adsorption reveals that MAC-4-OH shows a significant enhancement for CO2 uptake compared with that of MAC-4 due to the existence of electrostatic attractive interactions, though its surface area is lower than that of MAC-4.

Two novel zinc phosphonocarboxylates, Zn3(pbc)2(bpy)(H2O)·H2O (1) and Zn2(pbc)2·Zn(bpy)(H2O)4·2H2O (2) (pbc = 4-phosphono-benzoic acid, bpy = 2,2′-bipyridine), were hydrothermally synthesized and structurally characterized. Both of them exhibit zeolitic ABW topology in which double-zigzag inorganic chains are cross-linked by the organic parts. It is notable that the metal complex Zn(bpy)(H2O)x plays different roles in the two compounds. In 1, the Zn(bpy)(H2O) units coordinate with the phosphonate and carboxylate oxygen atoms and participate in the construction of the three-dimensional framework. In 2, the in situ generated [Zn(bpy)(H2O)4]2+ cation acts as a template, which directs the ABW-type open-framework by strong hydrogen bonds. It is the first example where a metal complex is used as a template in the synthesis of metal phosphonates. The luminescent properties of 1 and 2 are also investigated.

To systematically explore the assembly mechanism of a rutile-type open framework of {[Zn3(pbdc)2]·2H3O}n (3) (H4pbdc = 5-phosphonobenzene-1,3-dicarboxylic acid) constructed by 3-connected pbdc ligands and 6-connected Zn3(CO2)4(PO3)2 secondary building units (Zn3-SBUs), three major factors including solvothermal procedures, types of solvents and amines, are taken into consideration. Seven novel structures, namely {[Zn5(pbdc)2(OH)2(H2O)4]·4H2O}n (1), {[Zn3(pbdc)2·H2O]·(Htea)·H3O·2–5(H2O)}n (2), {[Zn3(pbdc)2](H3O)2(dma)}n (4), {[Zn2(pbdc)(taea)]·3H2O}n (5), {[Zn3(pbdc)2(Hpda)2]·2H2O}n (6), {[Zn5(pbdc)2(Hpbdc)2]·2H2pz·9H2O}n (7), {[Zn3(pbdc)2]·Hpd·H3O·4H2O}n (8) are obtained. The results indicate that the layered-solvothermal method and the isopropanol solvent play crucial roles in the construction of the special anionic open framework of [Zn3(pbdc)2]2−. Changing these two factors led molecular assembly away from the rutile-type open framework. However, amines play a variable role in the framework, which means that by using appropriate amines, molecular assembly could generate the open framework of [Zn3(pbdc)2]2− with pores decorated by amines. These results suggest a different approach towards decorating pores in anionic frameworks with precise structural information.