Construction of Zr-Metal-Organic Frameworks-Based Composite Materials toward Anhydrous Proton Conduction and Photocatalytic CO2 Reduction.

Metal-organic frameworks constructed from Zr usually possess excellent chemical and physical stability. Therefore, they have become attractive platforms in various fields. In this work, two families of hybrid materials based on ZrSQU have been designed and synthesized, named Im@ZrSQU and Cu@ZrSQU, respectively. Im@ZrSQU was prepared through the impregnation method and employed for proton conduction. Im@ZrSQU exhibited terrific proton conduction performance in an anhydrous environment, with the highest proton conduction value of 3.6 × 10-2 S cm-1 at 110 °C. In addition, Cu@ZrSQU was synthesized via the photoinduction method for the photoreduction of CO2, which successfully promoted the conversion of CO2 into CO and achieved the CO generation rate of up to 12.4 µmol g-1 h-1. The photocatalytic performance of Cu@ZrSQU is derived from the synergistic effect of Cu NPs and ZrSQU. Based on an in-depth study and discussion toward ZrSQU, we provide a versatile platform with applications in the field of proton conduction and photocatalysis, which will guide researchers in their further studies.

A porous Ti-based metal-organic framework for CO2 photoreduction and imidazole-dependent anhydrous proton conduction.

The anhydrous proton conductivity of Im@IEF-11 resulting from the integration of imidazole and porous IEF-11 has been investigated, and the highest proton conductive value can reach up to 7.64 × 10-2 S cm-1. Furthermore, IEF-11 is also developed to reduce CO2 due to its reasonable structure and suitable energy band, and its CO formation rate is 31.86 µmol g-1 h-1.

Ag Nanoparticle-Modified Polyoxometalate-Based Metal-Organic Framework for Enhanced CO2 Photoreduction.

The photoreduction deposition method is employed to fabricate a family of silver nanoparticle (Ag NP)-modified polyoxometalate-based metal-organic framework (NENU-5) photocatalysts, named Ag/NENU-5. The title photocatalysts, Ag/NENU-5, can be used for the photocatalytic reduction of CO2 and are observed to efficiently reduce CO2 into CO, in which the highest reduction rate is 22.28 µmol g-1 h-1, 3 times greater than that of NENU-5. Photocatalytic reduction performances of CO2 have been extremely improved after the incorporation of Ag NPs as the cocatalyst. The enhancement of the photocatalytic reduction of CO2 has been attributed to the synergistic effects of Ag NPs and NENU-5, inhibiting the charge recombination during the photocatalytic process and increasing the reaction active sites. Furthermore, the influence of Ag NPs on the photocatalytic activity has also been investigated. The experimental results clearly reveal that the size of Ag NPs could exert a main effect on the photocatalytic activity, and the reasonable size of Ag NPs is able to enhance the photocatalytic reduction activity toward CO2 significantly.

A multifunctional anionic metal-organic framework for high proton conductivity and photoreduction of CO2 induced by cation exchange.

Metal-organic frameworks (MOFs) provide an ideal platform for loading various guests owing to their available space, and can be developed as a class of multifunctional materials. Herein, we cover the design and synthesis of two kinds of exchanged frameworks with multifunctional applications based on H3ImDC and In(NO3)3·2H2O through guest exchange inside the framework. The guest ammonium ion (NH4+) and [Ru(2,2'-bipyridine)3]2+ (Rubpy) are selected to exchange the dimethylammonium cation (Me2NH2+) encapsulated within In-MOF, giving birth to two kinds of new MOFs, named NH4+@In-MOF and Rubpy@In-MOF respectively. The proton conduction of NH4+@In-MOF and the CO2 photoreduction of Rubpy@In-MOF are investigated. Under different test conditions, the proton conductive behaviors of NH4+@In-MOF are evaluated and the best proton conductive value can reach up to 9.81 × 10-3 S cm-1. Compared to the original In-MOF, Rubpy@In-MOF exhibits a significantly enhanced CO2 photoreduction performance under a pure CO2 atmosphere. Furthermore, its photocatalytic activity is retained even under a 10% CO2 gas atmosphere, displaying a synergistic effect between Rubpy and In-MOF24 within Rubpy@In-MOF.

Integration of zirconium-based metal-organic framework with CdS for enhanced photocatalytic conversion of CO2 to CO.

It is a promising strategy to prepare composite photocatalysts based on MOFs and semiconductors for enhancing photocatalytic reduction of carbon dioxide (CO2). A family of binary composite photocatalysts (CdS@UiO-66-NH2) with different CdS contents have been designed and synthesized, which have been explored for photocatalytic reduction of CO2. CdS@UiO-66-NH2 can efficiently convert CO2 into CO under visible light irradiation via the solid-gas mode in the absence of sacrificial agents and photosensitizers. The generation rate of CO can reach up to 280.5 µmol g-1 h-1, which is 2.13-fold and 2.9-fold improvements over the pristine CdS and UiO-66-NH2, respectively, and the selectivity for CO is very high. Furthermore, this kind of photocatalysts can still maintain great photocatalytic activity in CO2/N2 mixed atmosphere with different CO2 concentrations. The outstanding performances of CdS@UiO-66-NH2 may be attributed to the existence of the direct Z-scheme heterojunction, which possesses the enhanced separation and migration of photo-generated charge carriers between UiO-66-NH2 and CdS, available specific surface areas and improved visible light absorption ability as well as abundant reaction active sites. This case reveals that MOF-based composite photocatalysts exhibit promising potential applications in the field of CO2 conversion.

Two unprecedented porous anionic frameworks: organoammonium templating effects and structural diversification.

Two unprecedented 3D porous anionic metal-organic frameworks, [Me2NH2]2[Cd2(bpdc)3].4dma 1 and [Me2NH2]2[Cd2(NH2bdc)3].4dma 2 (dma = N,N'-dimethylacetamide, bpdc = 4,4'-biphenyldicarboxylate, NH(2)bdc = 2-amino-1,4-benzenedicarboxylate) have been solvothermally synthesized with a dimethylammonium cations template. Both 1 and 2 are constructed from low-symmetry SBUs. 1 has a chiral framework with helical nanotube-like channels, and 2 has a MOF-5-like motif. The fluorescence, N2 adsorption and ion-exchange properties for 1 have been examined.

Inorganic-organic hybrid materials with different dimensions constructed from copper-fluconazole metal-organic units and Keggin polyanion clusters.

Inorganic-organic hybrid materials based on Keggin polyoxometalate building blocks combined with Cu(II)/Cu(I) and flexible fluconazole ligand [1-(2,4-difluorophenyl)-1,1-bis[(1H-1,2,4-triazol-1-yl)methyl]methanol] (Hfcz) have been obtained by hydrothermal methods, namely, [Cu(II)(2)(Hfcz)(4)(SiW(12)O(40))].3H(2)O (1), [Cu(II)(4)(fcz)(4)(H(2)O)(4)(SiMo(12)O(40))].6H(2)O (2), [Cu(II)(2)(fcz)(2)][Cu(II)(4)(fcz)(4)(SiW(12)O(40))][Cu(II)(2)(fcz)(2)(H(2)O)(2)(SiW(12)O(40))].6H(2)O (3), (Et(3)NH)(2)[Cu(I)(2)(Hfcz)(2)(SiW(12)O(40))].2H(2)O (4), (Et(3)NH)(2)[Cu(I)(2)(Hfcz)(2)(SiW(12)O(40))].H(2)O (5) and [Cu(I)(4)(Hfcz)(4)(SiMo(12)O(40))] (6). Their structures have been determined by single-crystal X-ray diffraction analyses, and the compounds are further characterized by elemental analyses, IR spectra and thermogravimetric (TG) analyses. In 1, Cu(II) cations are bridged by fluconazole ligands to form a 3D lvt coordination polymeric network, which is connected by (SiW(12)O(40))(4-) anions to form a complicated 3D (4,6)-connected framework with the topology of (4(2).6(4))(4(6).6(7).8(2))(2). In 2, two fcz(-) anions chelate two Cu(2+) cations to form a [Cu(fcz)](2)(2+) dimer, which is bridged by (SiW(12)O(40))(4-) polyanions to generate a 2D (4,4) grid. Compound 3 is formed by three types of co-crystallizing subunits including a dimer [Cu(fcz)](2)(2+), a dumbbell molecule [Cu(4)(fcz)(4)(SiW(12)O(40))] and an infinite chain {[Cu(2)(fcz)(2)(H(2)O)(2)(SiW(12)O(40))](2-)}(infinity). In compounds 4 and 5, Hfcz ligands link Cu(+) cations to generate 1D coordination polymeric units, and (SiW(12)O(40))(4-) polyanions connect these metal-organic units to form two types of (6(3)) sheets which are topological isomerism. In compound 6, (SiMo(12)O(40))(4-) polyanions fixed in Cu(I)-Hfcz square rings are further extended into a 2D sheet via linking Cu(I) atoms of different rings. By carefully inspection of the structures of 1-6, it is believed that various transition-metal organic units and Keggin polyanions with different coordination modes are important for the formation of the different structures. In addition, electrochemical behaviors of compounds 1, 2, 5 and 6 have been investigated.

d(10)-Metal coordination polymers based on analogue di(pyridyl)imidazole derivatives and 4,4'-oxydibenzoic acid: influence of flexible and angular characters of neutral ligands on structural diversity.

A series of mixed-ligand coordination complexes, namely [Zn(L(1))(oba)] (), [Cd(L(1))(oba)] (), [Zn(2)(L(2))(oba)(2)].8H(2)O (), [Cd(2)(L(2))(oba)(2)].2H(2)O (), [Zn(3)(L(3))(oba)(3)] (), [Cd(2)(L(3))(oba)(2)].(L(3)) (), [Cd(L(4))(oba)].H(2)O () and [Cd(L(5))(oba)].3H(2)O (), where L(1) = 2-(2-pyridyl)imidazole, L(2) = 1,4-bis[2-(2-pyridyl)imidazol-1-yl]butane, L(3) = 1,4-bis[2-(2-pyridyl)imidazol-1-ylmethyl]benzene, L(4) = 1,3-bis[2-(2-pyridyl)imidazol-1-ylmethyl]benzene, L(5) = 1,2-bis[2-(2-pyridyl)imidazol-1-ylmethyl]benzene and H(2)oba = 4,4'-oxydibenzoic acid, have been synthesized under hydrothermal conditions. Their structures have been determined by single crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, and thermogravimetric (TG) analyses. In compounds and , oba(2-), L(1) ligand and Zn(II) or Cd(II) ions assemble to form the parallel chains or parallel sheets which are linked by the weak hydrogen bonding and pipi stacking interactions to give the 2D supramolecular sheet or 3D supramolecular net, respectively. For , L(2) ligands connect [Zn(oba)] chains to generate a unusual (10,3)-b topological structure which is the first example for eight-fold interpenetrating framework based on the (10,3)-b net. In , L(2) ligands link [Cd(oba)] double-chains to give a 2D sheet which is assembled by pipi stacking interactions to obtain a 3D supramolecular net. In , L(3) ligands link Zn(II) ions from alpha-Po net formed by Zn(II) ions and oba(2-) anions to show a novel 3D 8-connected self-penetrating framework with the unreported (4(16).6(11).8) topological structure. In , the double-chains constructed by Cd(II) and oba(2-) anions are linked by one kind of L(3) ligand to form a layer-like structure which is assembled by pipi stacking interactions to show a 3D supramolecular structure. In , oba(2-) anions coordinate to Cd(II) cations to form chains which are connected by L(4) to form a four-fold interpenetrating diamond network. In , the weak hydrogen bonding and pipi stacking interactions connect the [Cd(L(5))(oba)] chains to give a 2D supramolecular sheet. By careful inspections of the structures of , we believe that the different flexible and angular neutral ligands, coordination geometries of metal centers and weak interactions (hydrogen bonds and pipi stacking interactions) are crucial factors for the formation of the different structures. The photoluminescent properties of have been studied in the solid state at room temperature.

Tetra-aqua-bis(2-oxo-1,2-dihydro-quinoline-4-carboxyl-ato-κO)nickel(II).

In the title compound, [Ni(C(10)H(6)NO(3))(2)(H(2)O)(4)], the central Ni(II) atom is located on an inversion center and coordinated in a slightly distorted octa-hedral geometry by two O atoms from two 2-oxo-1,2-dihydro-quinoline-4-carboxyl-ate ligands and four water mol-ecules, all of which act as monodentate ligands. The crystal structure features an extensive network of inter-molecular hydrogen-bonding inter-actions (O-H⋯O and N-H⋯O) and offset face-to-face π-π stacking inter-actions [centroid-centroid distances = 3.525 (3) and 3.281 (5) Å].