Thiazolo[5,4-d]thiazole-Based Metal-Organic Framework for Catalytic CO2 Cycloaddition and Photocatalytic Benzylamine Coupling Reactions.

Metal-organic frameworks (MOFs) with permanent porosity and multifunctional catalytic sites constructed by two or more organic ligands are regarded as effective heterogeneous catalysts to improve certain organic catalytic reactions. In this work, a pillared-layer Zn-MOF (MOF-LS10) was constructed by 2,3,5,6-tetrakis(4-carboxyphenyl)pyrazine (H4TCPP) and 2,5-di(pyridin-4-yl)thiazolo[5,4-d]thiazole (DPTZTZ). After activation, MOF-LS10 has a permanent porosity and moderate CO2 adsorption capacity. The introduction of thiazolo[5,4-d]thiazole (TZTZ), a photoactive unit, into the framework endows MOF-LS10 with excellent photocatalytic performance. MOF-LS10 can not only efficiently catalyze the formation of cyclic carbonates from CO2 and epoxide substrates under mild conditions but also can photocatalyze benzylamine coupling at room temperature. In addition, we used another two ligands 1,2,4,5-tetrakis(4-carboxyphenyl)benzene (H4BTEB) and 1,4-di(pyridin-4-yl)benzene (DPB) to synthesize MOF-LS11 (constructed by BTEB4- and DPTZTZ) and MOF-LS12 (constructed by TCPP4- and DPB) in order to explore whether the pyrazine structural unit and the TZTZ structural unit synergistically catalyze the reaction. The electron paramagnetic resonance spectrum demonstrates that the superoxide radical (·O2-), generated by electron transfer from the MOF excited by light to the oxidant, is the main active substance of oxidation. The design and synthesis of MOF-LS10 provide an effective synthetic strategy for the development of versatile heterogeneous catalysts for various organic reactions and a wide range of substrates.

Zeolitic Open-Framework Borates with Noncentrosymmetric Structures and Nonlinear Optical Properties.

Three zeolitic pentaborates (H2en)[B5O8(OH)] (1, en = ethylenediamine), (Hen)2[Al(B5O10)] (2), (H2en)[NH(CH3)2][Al(B5O10)] (3) were solvothermally obtained by employing ethanediamine molecules as structure-directing agents (SDAs). The nonmetal borate of 1 features a noncentrosymmetric two-dimensional layered structure. Through introducing Al atoms as the linkers and regulating the reaction conditions of 1, two three-dimensional zeolitic open-framework aluminoborates, noncentrosymmetric (NCS) of 2 and centrosymmetric (CS) of 3, were achieved. Both 2 and 3 exhibit [Al(B5O10)] n2 n- zeolitic frameworks based on the same fundamental building blocks (FBBs). However, the different arrangements between two FBBs result in 2 showing a NCS framework with dia topology, while 3 presents CS framework with cag topology. The flexibility of linkages modes of the FBBs as well as the unique structure-directing functions play crucial roles in the different formations. Powder second-harmonic generation (SHG) measurements revealed that acentric 1 and 2 possess nonlinear optical activity and 2 is type I phase-matchable with SHG responses of ∼1.0 time for KDP (KH2PO4). Infrared and UV-vis diffuse reflectance spectroscopy, along with electronic structure calculations, were also performed for the materials.

A 3D Iodoplumbate Semiconducting Open Framework with Visible-light-induced Photocatalytic Performance.

Employing in situ N-alkylation of the conjugated compound 9,10-bis(4-pyridyl)anthracene (bpanth) as structure-directing agent, a 3D inorganic-organic hybrid iodoplumbate, [Me2 (bpanth)][Pb4 I10 ] (1), was solvothermally prepared. The in situ N-alkylation of bpanth with alcohols was investigated. 1 features a novel 3D open framework based on an interesting Pb6 I24 cluster. UV/Vis spectroscopy analyses indicate that 1 is a potential semiconductor material with a narrow energy gap of 2.06 eV. It exhibits good catalytic activity in the visible-light-drived degradation of an organic dye. This work further illustrates that introducing conjugated organic molecules as templates is conducive to achieving semiconducting hybrid halometallates with narrow band gaps.

Tripyridine-Derivative-Derived Semiconducting Iodo-Argentate/Cuprate Hybrids with Excellent Visible-Light-Induced Photocatalytic Performance.

Through regulating the pH values, a series of iodo-argentate/cuprate hybrids, [Me3 (4-TPT)]4 [Ag6 I18 ] (1, Me3 (4-TPT)=N,N',N''-trimethyl-2,4,6-tris(4-pyridyl)-1,3,5-triazine), [Me3 (4-TPT)][M5 I8 ] (M=Ag/2, Cu/2 a), [Me3 (3-TPT)][M5 I8 ] (Me3 (3-TPT)=N,N',N''-trimethyl-2,4,6-tris(3-pyridyl)-1,3,5-triazine, M=Ag/3, Cu/4), which exhibit adjustable structural variations with different dimensional structures, have been obtained under solvothermal conditions. They are directed by two types of in situ N-alkylation TPT-derivatives (Me3 (4-TPT) for 1/2/2 a and Me3 (3-TPT) for 3/4) and represent the isolated units (1), 1D polymeric chain (4), 2D layered structures (2/2 a, 3) based on diverse metal iodide clusters. These compounds possess reducing band gaps as compared with the bulk ß-AgI and CuI and belong to potential semiconductor materials. Iodocuprates feature highly efficient photocatalytic activity in the sunlight-induced degradation of organic dyes. The detailed study on the possible photocatalytic mechanism, including radical trapping tests and theoretical calculations, reveals that the N-alkylation TPT moieties contribute to the narrow semiconducting behavior and effectively inhibit the recombination of photogenerated electron-hole pairs, which result in an excellent visible-light-induced photocatalytic performance.

Three-Shell Cu@Co@Ni Nanoparticles Stabilized with a Metal-Organic Framework for Enhanced Tandem Catalysis.

Transition-metal catalysts, particularly featuring a triple-layered core-shell structure, are very promising for practical application; however, reports on their synthesis and catalytic application for a cascade reaction were very rare. In this work, tiny Cu@Co@Ni core-shell nanoparticles (∼3.3 nm) containing Cu core, Co middle shell, and Ni outer shell stabilized by metal-organic framework (MOF) were successfully synthesized to give a quadruple-layered Cu@Co@Ni/MOF at moderate conditions. The catalyst exhibited superior catalytic performance toward the in situ hydrogenation of nitroarenes using the H2 generated from the hydrolysis of ammonia borane (NH3BH3) under mild conditions. Interestingly, the Cu@Co@Ni/MOF also showed excellent catalytic activity toward CO oxidation reaction, which outperforms those of noble-metal catalysts. To our knowledge, this is the first report on transition-metal nanoparticles with a three-layered core-shell structure stabilized by MOF as a cooperative catalyst for cascade reaction and CO oxidation.