Kui-Zhan Shao

Highly Stable Crystalline Catalysts Based on a Microporous Metal-Organic Framework and Polyoxometalates

A series of remarkable crystalline compounds [Cu(2)(BTC)(4/3)(H(2)O)(2)](6)[H(n)XM(12)O(40)].(C(4)H(12)N)(2) (X = Si, Ge, P, As; M = W, Mo) were obtained from the simple one-step hydrothermal reaction of copper nitrate, benzentricaboxylate (BTC), and different Keggin polyoxometalates (POMs). In these compounds, the catalytically active Keggin polyanions were alternately arrayed as noncoordinating guests in the cuboctahedral cages of a Cu-BTC-based metal-organic framework (MOF) host matrix. X-ray crystallographic analyses, TG, FT-IR, UV-vis, N(2) adsorption studies, and acid-base titration demonstrated their high stability and toleration for thermal and acid-base conditions. No POM leaching or framework decomposition was observed in our study. The representative acid catalytic performance of a compound containing PW(12) species was assessed through the hydrolysis of esters in excess water, which showed high catalytic activity and can be used repeatedly without activity loss. Moreover, catalytic selectivity, which is dependent on the molecular size of substrates, and substrate accessibility for the pore surface were observed. It is the first time that the well-defined, crystalline, MOF-supported POM compound has behaved as a true heterogeneous acid catalyst. The unique attributes of MOF and well-dispersed level of POMs prohibited the conglomeration and deactivation of POMs, which allowed for the enhancement of their catalytic properties.

Chiral Nanoporous Metal‐Organic Frameworks with High Porosity as Materials for Drug Delivery

A chiral nanoporous metal-organic framework (MOF) with high porosity is obtained based on nontoxic zinc and achiral hexadentate ligand. It shows high drug loading and slow release of the proportion of the loaded drug with a complete delivery time of about one week when used as a material for adsorption and delivery of anticancer 5-fluorouracil.

N-rich zeolite-like metal–organic framework with sodalite topology: high CO2 uptake, selective gas adsorption and efficient drug delivery

A novel zeolite-like metal–organic framework (ZMOF) with sodalite topology, [Zn(HL)]·DMA (IFMC-1, L = 4,5-di(1H-tetrazol-5-yl)-2H-1,2,3-triazole and IFMC = Institute of Functional Material Chemistry), was solvothermally synthesized based on an N-rich aromatic ligand without a NH2 group. It exhibits high CO2 uptake and selective CO2/N2 adsorption capacity. For the first time, we investigated the influence of a large number of uncoordinated nitrogen atoms from aromatic rings for CO2 adsorption in ZMOFs. This result reveals that the high percentage of open N-donor sites leads to the high uptake capacity for CO2, even in the absence of any NH2 groups and open metal sites. In addition, it also exhibits efficient drug delivery capacity.

Self-Assembly and Photocatalytic Properties of Polyoxoniobates: {Nb24O72}, {Nb32O96}, and {K12Nb96O288} Clusters

Three novel polyoxoniobates, KNa(2)[Nb(24)O(72)H(21)]·38H(2)O (1), K(2)Na(2)[Nb(32)O(96)H(28)]·80H(2)O (2), and K(12)[Nb(24)O(72)H(21)](4)·107H(2)O (3) with molecular triangle, molecular square, and cuboctahedral molecular cage geometries, respectively, have been successfully synthesized by conventional aqueous methods. All the compounds are built from [Nb(7)O(22)](9-) fundamental building units. Compound 1 is the first isolated {Nb(24)O(72)} cluster, featuring three heptaniobate clusters linked in a ring by three additional NbO(6) octahedra, while compound 2 is the largest isopolyoxoniobate cluster reported to date, consisting of four heptaniobate clusters linked by four additional NbO(6) octahedra. Compound 3 is the largest solid aggregation of polyoxoniobates, assembled by four {KNb(24)O(72)} clusters joined by four K ions. To our knowledge, it is the first time these polyoxoniobate clusters have been crystallized with only alkali-metal counterions, thereby giving them the possibility of being redissolved in water. ESI-MS spectra indicate that compounds 1 and 2 remain structural integrity when the pure, crystalline polyanion salts are dissolved in water, while compound 3 is partially assembled into Nb(24) fragments. The UV-vis diffuse reflectance spectra of these powder samples indicate that the corresponding well-defined optical absorption associated with E(g) can be assessed at 3.35, 3.17, and 3.34 eV, respectively, revealing the presence of an optical band gap and the nature of semiconductivity with a wide band gap. UV-light photocatalytic H(2) evolution activities were observed for these compounds with Co(III)(dmgH)(2)pyCl as a cocatalyst and TEA as a sacrificial electron donor.

Construction and property investigation of transition-metal complexes modified octamolybdate hybrid materials based on V-shaped organic ligands

Six new transition-metal complexes modified octamolybdate compounds have been successfully synthesized with two kinds of V-shaped flexible organic ligands under hydrothermal conditions, namely, [CuII(HL1)2(H2O)2(Mo8O26)] (1), [CuII(L1)2(Mo8O26)0.5] (2), [CuII(HL2)2(Mo8O26)]·2H2O (3), [CuII2(L2)4(Mo8O26)]·3H2O (4), [CuI3(L2)2(Mo8O26)0.5Cl] (5), [CuI4(L2)4(Mo8O26)] (6) where L1 = 3-((1H-imidazol-1-yl)methyl)pyridine, L2 = 3-((1H-1,2,4-triazol-1-yl)methyl)pyridine. Their crystal structures have been determined by X-ray single-crystal diffraction, elemental analyses, IR spectra, and thermogravimetric analyses (TGA). With L1 ligand, two compounds were obtained: compound 1 is a 1D β-octamolybdate based chain and compound 2 is a 2D 4-connected network most strikingly, whose octamolybdate anion shows a θ-isomer. With L2 ligand, compounds 3, 4, 5 and 6 were obtained, respectively. In compound 3, 1D β-octamolybdate-based metal–organic chains are further extended by hydrogen bonds to build a 3D supramolecular structure, while in compound 4, every two adjacent double-helical metal–organic chains are bridged by β-octamolybdate anions to generate a 2D 3-connected network. When CuSO4·5H2O was substituted by CuCl, two CuI compounds were attained. Interestingly, in compound 5 the octamolybdate anion threads through the metal–organic loop presenting a fascinating 2D polythreading topology, and in compound 6 the octamolybdate anions pillar the railroad-like metal–organic strands to generate a 2D 3-connected network. The structural differences among compounds 1–6 indicate the importance of the different coordination mode of organic ligands and various polyoxoanions, and of the pH values of the systems for the framework formation. Furthermore, the semiconducting properties of compounds 1–5 were investigated, and photoluminescence as well as photoconductivity for compound 5 were also studied. Compound 5 has a comparatively lower band gap and is photoconductive in the UV-vis range, so it can be potentially applied as a semiconductor of photoelectronic detectors.

Two eight-connected self-penetrating porous metal–organic frameworks: configurational isomers caused by different linking modes between terephthalate and binuclear nickel building units

Two novel nanoporous metal–organic frameworks (MOFs) based on the same binuclear nickel secondary building units, {[Ni2(H2O)(BDC)2(BIMB)2]·6DMF}n (1) and {[Ni2(H2O)(BDC)2(BIMB)2]·5DMAc}n (2) (H2BDC = terephthalic acid, BIMB = 1,4-bis(1-imidazolyl)benzene and DMF = N,N′-dimethylformamide, DMAc = N,N′-dimethylacetamide) have been synthesized by self-assembly of Ni(NO3)2·6H2O, BIMB and H2BDC in different solvents (DMF and DMAc), respectively. Different linking modes between terephthalate and binuclear nickel building units in 1 and 2 lead to an interesting phenomenon that their host frameworks are isomeric to each other and have the same three periodic eight-connected self-penetrating nets with novel 420.68 topology. Powder X-ray diffraction (PXRD) results indicate that 1 and 2 both have reversible framework transformations in an acetone/guest solvent molecule system.

Polyoxometalate-based crystalline tubular microreactor: redox-active inorganic–organic hybrid materials producing gold nanoparticles and catalytic properties

Here, we synthesize a novel polyoxometalate-based crystalline tubular inorganic–organic compound, Mn[Zn(im)]2{[Na(H2O)]2[Mn(H2O)2][Zn(im)2][P4Mo6O31H6]2}·8H2O (IFMC-100) (im and IFMC correspond to imidazole and Institute of Functional Material Chemistry, respectively). Au-anchored tubular microreactor, Au@IFMC-100, has been prepared by simple immersion of IFMC-100 in an ethanol solution of HAuCl4 without any extra reducing agents, photochemical and electrochemical auxiliaries. Furthermore, IFMC-100 and Au@IFMC-100 have been employed as catalysts for the reduction of K3Fe(CN)6 and 4-nitrophenol with NaBH4 in aqueous solution, respectively. The results indicate the as-prepared Au@IFMC-100 microtubes exhibit enhanced catalytic performance in redox catalysis.

pH-dependent self-assembly of divalent metals with a new ligand containing polycarboxylate: syntheses, crystal structures, luminescent and magnetic properties

Six new coordination polymers, namely, [Cd(HL)(4,4′-bpy)(H2O)]·H2O (1), [Cd3(L)2(4,4′-bpy)3(H2O)]·2.5H2O (2), [Co(HL)(4,4′-bpy)]·H2O (3), [Co2(L)(4,4′-bpy)0.5(μ3-OH)(H2O)2]·H2O (4), [Zn(HL)(BIMB)]·2H2O (5), [Zn3(L)2(BIMB)2]·3H2O (6), where H3L = 5-(4-carboxybenzyloxy)isophthalic acid, 4,4′-bpy = 4,4′-bipyridine, BIMB = 1,4-di(1H-imidazol-1-yl)benzene, have been synthesized under hydrothermal conditions and characterized by single crystal X-ray diffraction. In complexes 1, 3 and 5, H3L ligand is partially deprotonated in the form of HL2−; while in 2, 4 and 6, it is completely deprotonated due to the influence of different pH values. Complexes 1 and 5 are 2D layer structures, the hydrogen bonds between lattice-water molecules and carboxylate groups of HL2− ligands extend the 2D layer into a 3D framework; while complex 3 is a 3D framework with α-Po topology. Complex 2 is a 3D fourfold interpenetrating (3,4,4)-connected net with (63)(62·84)(64·82) topology. Complex 4 is a twofold interpenetrating (3,8)-connected net with (43)2(46·618·84) topology. And complex 6 is a twofold interpenetrating (3,4,6)-connected net with (4·62)(64·72)(42·66·74·8·92) topology. In addition, powder X-ray diffraction and thermogravimetric analyses for 1–6, photoluminescent properties for 1, 2, 5, 6 and magnetic properties for 3, 4 are investigated in detail.

Construction of different dimensional inorganic-organic hybrid materials based on polyoxometalates and metal-organic units via changing metal ions: from non-covalent interactions to covalent connections.

Five POM-based hybrid materials have been designed and synthesized based on different metal ions under hydrothermal conditions, namely, [Zn(Hfcz)(H(2)O)(3)](H(3)fcz)(SiMo(12)O(40)).3H(2)O (1), [Cd(2)(Hfcz)(6)(H(2)O)(2)](SiMo(12)O(40)).H(2)O (2), [Co(2)(Hfcz)(2)(SiW(12)O(40))](H(3)fcz)(2)(SiW(12)O(40)).10H(2)O (3), [Ni(2)(Hfcz)(4)(H(2)O)(2)](SiW(12)O(40)).5H(2)O (4) and [Ag(4)(Hfcz)(2)(SiMo(12)O(40))] (5), where Hfcz is fluconazole [2-(2,4-difluorophenyl)-1,3-di(1H-1,2,4-triazol-1-yl)propan-2-ol]. Their crystal structures have been determined by X-ray diffraction, elemental analyses, IR spectra, and thermogravimetric analyses (TGA). There are 1D mono and double chain-like metal-organic units in compounds 1 and 2, respectively. Polyoxometalates and metal-organic units co-crystallize through hydrogen bonds. In compound 3, metal-organic sheets are pillared by one kind of polyanion through covalent connections to generate a sandwich double-sheet. The other kind of polyanion acts as a counter-ion and lies in two adjacent sandwich double-sheets through non-covalent interactions. Polyanions covalently link metal-organic sheets to extend to an unusual 3D 5-connected framework with the (4(4).6(6)) topology in 4. In compound 5, polyanions link metal-organic chains to form a sheet through covalent connections. It is interesting that compound 5 shows an intricate (4,5,10)-connected framework with (4(4).6(2))(4)(4(8).6(2))(2)(4(14).6(19).8(12)) topology based on two kinds of Ag cations as four-connected and five-connected nodes, and polyanions as ten-connected nodes, when AgO interactions are considered. It represents the highest connected network topology presently known for polyoxometalate systems. The structural differences among 1-5 indicate the importance of different metal-organic units, coordination modes of polyanions for framework formation, and the interactions between polyanions and metal-organic units. In addition, the luminescent properties of compounds 1, 2 and 5, and electrochemical behaviours of compounds 1-5 have been investigated.

Remarkable solvent-size effects in constructing novel porous 1,3,5-benzenetricarboxylate metal–organic frameworks

Seven novel porous metal–organic frameworks (MOFs), Zn2(BTC)(NO3)(DMA)3 (1), Zn11(BTC)6(NO3)4(DEE)9 (2), Zn11(BTC)6(NO3)4(DEP)8 (3), Zn(BTC)·DMA·C2H8N (4), Zn3(BTC)3·3(C2H8N)·4(DMA) (5), Zn9(BTC)6(OH)2·2(C2H8N)·15(DEE) (6), and Zn9(BTC)5(OH)3(C2O4)·2(C4H12N)·5(DEE) (7) have been solvothermally synthesized using zinc nitrate, 1,3,5-benzenetricarboxylate acid (H3BTC) and differently sized solvents (DMF, DMA, DEE, DEP, DPE, DPP), showing that the solvent size can not only dramatically influence the pore size, but also allow access to new structures and topologies previously unrealized in MOFs. With increasing solvent size, the pore size of MOFs correspondingly changes from 9 A to 23 A along with different structures: three frameworks have cages larger than 16 A, one has a 23 A chiral cage, five are anionic frameworks, three have topologies heretofore unreported in MOFs and all structures are noninterpenetrating. The ion-exchange experiment estimated by HNMR analyses shows that dimethylamine ions in 5 can be exchanged by NH4+ ions.