Construction And Photocatalytic Performance Research Of Highly Efficient Metal-organic Framework And Sulfide Heterojunction

The photocatalysis technology can convert clean and renewable solar energy into chemical energy directly,widely used to solve environmental and energy problems.However,the low solar energy conversion efficiency of photocatalysts is the critical issue restricting its further development.How to expand its visible light response and improve the separation and migration rate of photogenerated charge carriers have become the focus of research in this field.Due to its structural diversity and tunability,MOF can be used to construct various functional MOF-based photocatalysts through the modification of metal/metal clusters,organic linkers,pores and surface functional groups,which can settle the current problems in the field of photocatalysis and provide more possibilities for solving the environmental and energy crisis.Based on the structural tunability and semiconductor-like nature of MOF,we designed and synthesized two kinds of MOF-based heterojunction with new photosensitive sites and catalytic sites for CO₂reduction and degradation of toluene,which provides a new platform for the effective transfer of electrons.Based on the derivation characteristics of MOF,a MOF/MOF-derived homologous semiconductor/MOF hollow tubular sandwich heterojunction In₂S₃@NH₂-MIL-68（In）@In₂S₃（denoted as SMS（In））was generated in situ via a controllable sulfuration process for the first time.Fourier Transform infrared spectroscopy and Scanning/transmission electron microscope showed the chemical composition,structure and morphology of the material during the sulfuration process,and the intimate and ordered heterojunction interface between NH₂-MIL-68（In）and In₂S₃was confirmed by HRTEM.Benefiting from this unique hollow homologous heterojunction,SMS（In）-7 exhibits the highest CO evolution rate of 11.23μmol g^-1h^-1,which was approximately 2 times and 2.5 times of In₂S₃and NH₂-MIL-68（In）,respectively.This indicated the synergistic effect between NH₂-MIL-68（In）and In₂S₃.The transient/steady-state fluorescence spectra demonstrated that the successful construction of efficient heterojunctions effectively promotes the electron separation and transfer of composite photocatalyst,and the possible photocatalytic reduction mechanism of CO₂is proposed.This work demonstrates a novel insight in utilization of MOFs-based platform for the efficient atomically heterojunction design.The Cd S@MIL-101（Cr）composite photocatalyst is successfully synthesized,in which the precursor is introduced through the"double solvent impregnation method",achieving the in-situ growth of inorganic semiconductor quantum dots Cd S in the pore.The electronic interaction between Cd S and MIL-101（Cr）was investigated by Raman and X-ray photoelectron spectroscopy,and the synergistic effect was confirmed in the experiment of photocatalytic degradation of toluene.Under visible light conditions,the toluene removal rate of Cd S@MIL-101（Cr）composite reached 91.8%,which have increased by 55%and 102%compared with MIL-101（Cr）and Cd S,respectively.Besides,the mineralization rate of Cd S@MIL-101（Cr）reached 34%and is also higher than MIL-101（Cr）and Cd S.This benefited from:1)The porous structure and high specific surface area of MIL-101（Cr）promoted the adsorption and aggregation of toluene,thus improving the substrate activation and catalytic conversion;2)MOF introduces new reaction sites and provides a platform for the electron transfer of Cd S,thus effectively inhibiting photogenerated electron-hole recombination.