Photocatalytic Multielectron Reduction of Nitroarenes to Anilines by Utilizing an Electron-Storable Polyoxometalate-Based Metal–Organic Framework

Abstract

A powerful approach to generate photocatalysts for the highly selective reduction of nitrobenzene using light as the driving force is a combination of photosensitizers and electron-storable components in a cooperative photocatalysis fashion. Herein, a new precious metal-free photocatalyst, {ZnW-TPT}, was prepared by incorporating a Zn-substituted monovacant Keggin polyanion [SiZnW11O39]6– and a photoactive organic bridging link 2,4,6-tri­(4-pyridyl)-1,3,5-triazine (TPT) into a framework. In this structure, the direct coordination bond between [SiZnW11O39]6– and the TPT ligand and the π–π interactions between TPT molecules help separate and migrate photogenerated carriers, which improves the photocatalytic activity of {ZnW-TPT}. The photoelectrochemical properties of {ZnW-TPT} were well studied by solid UV–vis absorption, fluorescence, transient photocurrent response, and electrochemical impedance spectroscopy tests. {ZnW-TPT} efficiently converts using hydrazine hydrate with 99% conversion and 99% selectivity for anilines under mild conditions.

Bifunctional {Pb10K2}–Organic Framework for High Catalytic Activity in Cycloaddition of CO2 with Epoxides and Knoevenagel Condensation

“…Metal–organic frameworks (MOFs), as a novel crystalline hybrid material self-assembled from versatile inorganic secondary building units (SBUs) and functional organic linkers, have attracted widespread attention because of the promising applications in the fields of gas storage/separation, heterogeneous catalysis, energy harvesting, air and water purification, biomedicine, etc. − In general, the nature of the metal ions in inorganic SBUs is essential for the final structures and target properties of the self-assembled MOFs. However, only transition- or lanthanide-based MOFs at present have been well-established and intensively studied. − By contrast, main group metals in the areas of s- and p-block are not paid much attention yet except for the limited reports on the hard acidic cations of Al 3+ , In 3+ , and Mg 2+ , − which should be attributed to the nonclassical coordination and flexible geometry. Specifically, the Pb­(II) ion characterizes an undefinable coordination number ranging from 2 to 12 because of its stereochemically active 6s 2 electrons with an “inert-pair effect”, , which undoubtedly leads to the unpredictable coordination geometry and directivity during the process of “accidental self-assembly” .…”

Fluorine-Functionalized NbO-Type {Cu2}-Organic Framework: Enhanced Catalytic Performance on the Cycloaddition Reaction of CO2 with Epoxides and Deacetalization-Knoevenagel Condensation

“…However, it is still a tremendous challenge for accurately designing and controlling the microstructure of MOF materials, by which the density of active sites and the intrinsic activity of active sites can be hoisted. Recent studies have proved that high catalytic activity of MOF materials can be achieved by modifying the ligands of MOF materials with functional groups. − In recent years, the introduction of Lewis basic sites such as −NH 2 and −CH 3 onto the nanochannel of MOFs has aroused widespread concern, by which the synergistic catalysis of acid–base sites to further improve their catalytic activity can be realized. − So far, Lewis basic functional groups, such as hydroxyl, amino, carboxyl, imidazole, and pyridine, have been successfully applied to functionalize the channels of MOFs, which, as expected, exhibit superior performance for the adsorption of CO 2 , selective and efficient catalysis for specific organic reactions, and the capture of toxic war gas.…”

An intriguing tetranuclear Rh-based polyoxometalate for the reduction of nitroarene and oxidation of aniline

“…3,4 Although the conversion of nitrobenzene to aniline has gotten a lot of attention in recent years, it also faces environmental and economic obstacles. 5,6 Thus, developing a photo-catalyst with a suitable energy level capable of efficiently triggering the reduction of nitrobenzene to aniline under visible light illumination possesses considerable research interest under these circumstances.…”