Strategic synergism in CO2 and biomass valorization into sustainable solar fuels via stable hybrid halide perovskites: unlocking untapped potential

Abstract

Sunlight-driven integration of photocatalytic CO₂ reduction with biomass feedstock valorization constitutes a highly efficient strategy for the synergistic production of multi-electron products and high-value fine chemicals, adhering to photo-chemical circular economy and sustainability. To date, no halide perovskite has been utilized for CO₂ reduction coupled with biomass oxidation as the development of more stable, efficient, reusable, and non-toxic halide perovskites continues to be challenging. Herein, we report the room-temperature synthesis of methylammonium tin bromide (MA₂SnBr₆) quantum dots (QDs), a vacancy-ordered hybrid halide perovskite (HHP), without additional capping agents. These novel QDs maintain structural integrity in air, moisture, and polar solvents, addressing a significant issue associated with halide perovskites. Remarkably, the MA₂SnBr₆ QDs remain stable under ambient conditions even after 1 year, as confirmed by PXRD analysis. Interestingly, MA₂SnBr₆ achieved exceptionally high electron consumption rates (R_e) of 5110 μmol g⁻¹ h⁻¹ and 12 383 μmol g⁻¹ h⁻¹ for CO₂ reduction under simulated and natural sunlight, respectively, outperforming previous systems. In situ transient studies demonstrate that the photogenerated electrons of MA₂SnBr₆ diffuse from the conduction band to trap states, reducing CO₂, while synergistically photogenerated holes oxidize biomass-derived alcohols. Additionally, in situ EPR experiments were performed to unravel mechanistic insights. Computational studies identify the Br p-orbitals of MA₂SnBr₆ as the reaction centre for CO₂ reduction. Consequently, this work introduces a lead-free, single-component material that operates without a co-catalyst, sacrificial agent or redox additive, offering a promising path towards achieving photoredox processes in a more sustainable and efficient manner.