The Study On The Preparation Of Two-dimensional Porphyrin-based MOF Composites For Photocatalytic/Electrocatalytic Performance

Metal-organic framework materials(MOFs),as new organic-inorganic hybrid materials,are widely used in photocatalysis and electrocatalysis due to their high specific surface area,easily tunable pore structure and the diversity of building blocks.However,most 3D MOF materials have wide band gaps and long carrier migration paths,which limit their further applications in this field.The recent emergence of two-dimensional porphyrin MOF materials,which are rich in basic sites,have a wide spectral range and short carrier migration distance,facilitate the adsorption of acidic substrates and the transport of charge carriers,thus improving their photocatalytic/electrocatalytic efficiency.However,single two-dimensional porphyrin MOF materials still face the problems of easy and rapid charge carrier complexation,which greatly limits their catalytic efficiency.Based on this,two different types of two-dimensional porphyrin MOF composites were constructed by compounding them with semiconductor materials such as black TiO₂or g-C₃N₄to investigate the performance of photocatalytic degradation of bisphenol A and electrocatalytic reduction of CO₂,respectively,in this paper,with the following main studies.(1)In this paper,2D porphyrin Co-TCPP MOF modified 2D B-TiO_2-Xnanosheets were prepared by hydrothermal method.Based on 2D-2D heterojunction can effectively promote the separation and transfer of photogenerated electron-hole pairs at the interface.It was found that the photocatalytic degradation efficiency of BPA could reach 97%after 120 min of visible light irradiation at a mass ratio of 10%of Co-TCPP MOF,while the catalyst exhibited excellent stability.In addition,the reaction pathway of BPA degradation was investigated,and the main active species for BPA degradation was found to be·O₂^-.In addition,the degradation pathway of BPA in this composite was investigated and a possible photocatalytic mechanism was proposed.(2)In this paper,two-dimensional Co-(Co+Cu)PMOF nanosheets(g-C₃N₄@Co-(Co+Cu)PMOF)modified with two-dimensional nanosheets g-C₃N₄were prepared by hydrothermal method to form 2D-2D heterojunctions,and the electrocatalytic activity of CO₂RR was evaluated.Electrochemical tests showed that g-C₃N₄@Co-(Co+Cu)PMOF-50%has a larger capacitance of 35.5 m F/cm₂and a higher carbon monoxide Faraday efficiency of 97.8%.Finally,based on DFT calculations,the electron flow from g-C₃N₄to Co-(Co+Cu)PMOF at the interface makes the Co-(Co+Cu)PMOF surface more enriched in electrons and therefore has the best catalytic performance.And the electrocatalytic mechanism of CO₂RR is proposed.