Oxygen Defect Engineering Boosts Photocatalytic CO₂ Cycloaddition Reaction With a Solar-to-Chemical Conversion Efficiency of 0.6%

Solar-driven conversion of CO₂ into high-value cyclic carbonates is considered an ideal carbon emission reduction strategy but synchronously faces the challenges of a low reaction rate and an unclear catalytic mechanism. Herein, oxygen vacancy-rich Bi₄NbO₈Cl (BNOC-OVs) are fabricated as CO₂ cycloaddition photocatalysts via a facile calcination strategy in a CO atmosphere. The introduction of OVs creates a high density of lattice disorder defects, which offers abundant Lewis acidic-basic active sites to efficiently drive the cycloaddition reaction. Crucially, both experimental data and density functional theory (DFT) computations demonstrate that OVs enhance the adsorption energies of substrate molecules and reduce the catalytic reaction barriers via regulating surface properties and electronic structure. As a result, BNOC-OVs2 exhibits an outstanding photocatalytic performance for the cycloaddition reaction of CO₂ and 1,2-epoxybutane, with a 1,2-butylene carbonate formation rate of 9224.5 μmol·g^-1·h^-1, much superior to other bismuth-based photocatalysts and a state-of-the-art catalyst system with the same substrates. For the first time, the solar to chemical (STC) conversion efficiency for photocatalytic CO₂ cycloaddition reaction is determined, which is up to 0.6%. This study offers an innovative pathway toward fabricating high-performance photocatalysts by modulating surface engineering and offers creative insight into the mechanism of photocatalytic CO₂ cycloaddition reactions.