Boosted charge transfer and CO₂ photoreduction by construction of S-scheme heterojunctions between Cs₂AgBiBr₆ nanosheets and two-dimensional metal–organic frameworks

A lead-free Cs₂AgBiBr₆ double perovskite is emerging as a promising candidate to replace toxic lead halide perovskites because of its environmental friendliness and impressive stability. However, the applications of Cs₂AgBiBr₆ (CABB) in photocatalytic CO₂ reduction are restricted by its poor charge separation and low CO₂ capturing ability. Herein, we report a novel inorganic/organic hybrid photocatalyst by coupling two-dimensional (2D) CABB nanosheets (NSs) with 2D Ni-based metal–organic framework (Ni-MOF) NSs. Systematic studies suggest the formation of an S-scheme heterojunction between CABB and the Ni-MOF, which facilitates the separation of photogenerated charge carriers and preserves the high redox potential of the hybrid. The Ni-MOF also serves as a CO₂ capturing agent to facilitate the surface reaction. These remarkable features endow the CABB/Ni-MOF hybrid with significantly enhanced photocatalytic CO₂ reduction performance, which is 6.43 and 8.79 times higher than that of solitary CABB and Ni-MOF, respectively. This study offers a novel photocatalytic system based on lead-free double perovskites and MOFs, which sheds light on fabricating highly efficient photocatalysts for artificial photosynthesis.