Study On The Preparation Of Cs₂AgBiBr₆/MIL-101（Fe） And Its Photocatalytic Performance In CO₂ Reduction Coupled With Methanol Oxidation

The massive use of conventional fossil fuels has led to ever-increasing energy and environmental concerns,thus reducing carbon emissions has become a global consensus.Among various strategies for carbon mitigation,converting carbon dioxide（CO₂）into high value-added chemicals over catalysts with clean and abundant solar energy is considered to be one of effective ways to maintain the carbon balance in nature.Nevertheless,the economic benefits of photocatalytic CO₂ reduction systems nowadays are limited by low conversion efficiency or the use of expensive sacrificial reagents.To address these problems,this thesis proposed the strategy of coupling photocatalytic CO₂ reduction and methanol oxidation to gain the same product,which improves the efficiency of photocatalytic CO₂ reduction while avoiding the waste of photogenerated holes and the use of expensive sacrificial reagents,effectively improving the economic benefit of photocatalytic CO₂ system.The details of the work are as follows.（1）Based on the nano spatial confinement effect of porous metal-organic framework materials,a series of Cs₂Ag Bi Br₆/MIL-101（Fe）composites were successfully prepared by in situ encapsulation of lead-free double perovskite Cs₂Ag Bi Br₆ in the pores of metal-organic framework MIL-101（Fe）using a simple one-pot method.It is shown that the Cs₂Ag Bi Br₆ quantum dots are uniformly dispersed in the pores of MIL-101（Fe）,and type II heterojunction is formed between the two components.In addition,there is strong electronic coupling between Cs₂Ag Bi Br₆ and MIL-101（Fe）in Cs₂Ag Bi Br₆/MIL-101（Fe）owing to the tight contact interface.Furthermore,the porous property of MIL-101（Fe）endows the Cs₂Ag Bi Br₆/MIL-101（Fe）composites with good CO₂ uptake ability.（2）A photocatalytic reaction system for CO₂ reduction coupled with methanol oxidation was constructed,and the above Cs₂Ag Bi Br₆/MIL-101（Fe）composites were introduced as bifunctional catalysts.Photophysical studies showed that the strong electronic coupling between Cs₂Ag Bi Br₆ and MIL-101（Fe）leads to the effective separation of photogenerated electrons and holes in Cs₂Ag Bi Br₆/MIL-101（Fe）through dual charge transfer pathway,which accumulate on MIL-101（Fe）and Cs₂Ag Bi Br₆,respectively.Based on the Cs₂Ag Bi Br₆/MIL-101（Fe）bifunctional photocatalyst,CO₂ reduction and methanol oxidation to the same high value-added product formic acid（selectivity of 97.8%）are achieved for the first time with a yield of 1375μmol g^-1 h^-1,which is more than 14 times that of pristine MIL-101（Fe）.The above work provides a new strategy for the design of environmentally friendly,low-cost and high-efficiency artificial photosynthesis systems,further broadening the application of metal halide perovskite and metal-organic framework materials in the fields of catalysis and energy conversion.