Mof-derived Catalyst@Photosensitizers Composite Systems For Photocatalytic Water Splitting And CO₂ Reduction

Global energy and environmental issues have caused widespread concern.Photocatalytic chemical conversion processes（including hydrogen（H₂）generation from water,carbon dioxide（CO₂）reduction,organic chemical reactions and pollutant degradation）can convert solar energy into chemical energy,a very promising way to solve energy and environmental problems.As a new type of porous crystal material,metal organic framework（MOF）have become promising candidates in the field of heterogeneous catalysis due to their high surface area,diverse structure,and adjustable pore size.Recently,more and more attention has focused on the development of MOF-supported/derived composites as heterogeneous catalysts.（1）Photocatalytic CO₂ reduction to syngas（CO and H₂）is one of the effective strategies to recycle CO₂ as a value-added product.Based on this,we designed a simple and effective self-assembly strategy to introduce photosensitizer（PS）and catalytically active center Co into MOF to obtain MOF composite material（Co/Ru）_n-Ui O-67（bpydc）,and thus realized the integration of PS and catalytic active sites in MOF molecules to build single-site catalyst@photosensitizer composite catalytic systems.The composite system can realize rapid multi-electron transfer from PS to catalyst under visible light irradiation,thereby achieving efficient preparation of syngas,and its activity is increased by 29.2 times compared with corresponding homogeneous catalytic system.This study extends the use of MOF composites to photocatalytic CO₂ reduction to produce syngas,providing an effective strategy for CO₂ recycling.（2）The application of molecular catalysts has been limited due to problems such as instability and difficulty in recycling.Here,we encapsulate the molecular catalyst into phosphorescent MOF Ru-Ui O-67 by immersion method to build MOF composite binuclear cluster@photosensitizer composite catalytic system for photocatalytic reduction of CO₂.Cyclic experiments and powder X-ray diffraction analysis（PXRD）before and after the reaction confirmed the stability of the composite.This work encapsulates the molecular catalyst into the MOF pores to make the homogeneous catalyst heterogeneous,improve the catalytic activity of the molecular catalyst,and effectively solve the problem that the molecular catalyst is difficult to separate and cannot be reused.（3）In photocatalytic systems,the use of photogenerated electrons to decom pose water to produce hydrogen and the use of photogenerated holes to achieve the production of high value-added chemicals is one of the goals of artificial photosynthesis research.This is still a huge challenge due to the effect of the catalyst’s redox capacity.Here,small-sized Co₉S₈@Cd S heterojunction was prepared by sulfuration of bimetal Co/Cd-MOF.Under visible light irradiation,the heterojunction can efficiently split water to generate H₂ and selectively oxidize benzyl alcohol to benzaldehyde.We have further confirmed that the heterojunction has high catalytic activity and stability through cycle experiment and characterization of the heterojunction after the reaction.In this study,the MOF-derived Z-type heterojunction was used as a catalyst to achieve the preparation of photocatalytic H₂ and high value-added chemicals without adding sacrificial agents.