Preparation Of Porphyrin MOF Modified-ZnTi-LDH Heterogeneous Materials And Their Performance For Photocatalytic Reduction Of CO₂

In order to meet the increasing energy demand,CO₂ from fossil fuel combustion is emitted and accumulated in large quantities,which increases the concentration of CO₂ in the atmosphere and intensifies the greenhouse effect.Mimicking natural photosynthesis,photocatalytic reduction of CO₂ to carbon-based products is an attractive research direction in the field of energy regeneration and storage,and an effective and promising solution to the above problem.Among different photocatalysts,Layered bimetallic hydroxides（LDH）is widely used in CO₂ reduction due to their low cost and eco-friendliness,but the limited redox potential and low charge separation efficiency of single LDH leads to low photocatalytic efficiency.In recent years,the strategy of modifying photocatalysts by constructing heterojunction structures to improve photocatalytic activity has received much attention.Therefore,in this paper,ZnTi-LDH was used as the main catalyst and suitable porphyrin MOF were selected to construct heterojunctions with it to investigate the photocatalytic CO₂ reduction performance of ZnTi-LDH heterojunction catalysts modified by porphyrin MOF in full spectral response.The main research contents are as follows:（1）ZnTi-LDH/Cu-FeTCPP MOF heterojunction catalysts were prepared by a surfactant-assisted method for photocatalytic CO₂ reduction.Compared with the pristine ZnTi-LDH and Cu-FeTCPP MOF nanosheets,the ZTCF-1 composite coupled with 1%Cu-FeTCPP MOF and ZnTi-LDH exhibited significantly enhanced photocatalytic activity under full-wavelength irradiation with a CO yield of 37.80μmol·g^-1,which was 28 and 26 times higher than that of ZnTi-LDH and Cu-FeTCPP MOF,respectively,due to its enhanced light absorption capacity and CO₂ adsorption capacity.In addition,the tight contact interface of 2D/2D materials facilitates charge transfer and exposes more catalytically active sites.More importantly,the direct Z-type heterojunction established at the interface of ZnTi-LDH and Cu-FeTCPP MOF can effectively suppress the complexation of electrons and holes and exhibit stronger redox ability,thus showing good photocatalytic activity.The photocatalytic mechanism of Z-type charge transfer is proposed by combining the characterization means of XPS,UPS and EPR.（2）A novel CuO QDs/ZnTi-LDH/Cd-TCPP MOF double Z-type heterojunction photocatalyst was synthesized by electrostatic adsorption and surfactant-assisted method,and its performance for photocatalytic CO₂ reduction was investigated in the full spectrum.Compared with pure ZnTi-LDH,CuO QDs/ZnTi-LDH and Cd-TCPP MOF/ZnTi-LDH,the prepared CZC-5 composites exhibited significantly enhanced photocatalytic performance with the yields of CO and CH₄ reaching 35.17μmol·g^-1and 3.56μmol·g^-1,which were 8.3 and 6.7 times higher than those of pure ZnTi-LDH,respectively.The improved activity is attributed to the construction of 0D/2D/2D double Z-type heterojunctions between ZnTi-LDH and CuO QDs and Cd-TCPP MOF,which not only can effectively separate the photogenerated electron-hole pairs and improve the utilization of photogenerated carriers,but also enhance the redox ability.Finally,the mechanism of reduction reaction was studied and discussed by means of XPS characterization.