Photoinduced Charge Transfer between Metal Halide Perovskite and Ru-Polypyridyl Complexes Toward Biocatalytic Reactions

Vacancy-ordered Bi-based perovskites, such as Cs₃Bi₂Br₉ (CBB), exhibit relatively high Lewis acidity due to Bi³⁺ centers, providing favorable acidic sites for organic transformations. Coupled with their tuneable optoelectronic properties, these features render CBB an efficient photocatalyst for various acid-catalyzed reactions. In this study, CBB is conjugated with a classical Ru(II)-polypyridyl photosensitizer (RuPS) to form a hybrid material, CBB/RuPS, capable of facilitating thermodynamically favourable inner-sphere electron transfer. This process yields the reduced RuPS radical anion (RuPS^•−) and a hole (h⁺) in the oxidized CBB species. Ultrafast charge recombination is suppressed through an efficient extraction of e− and h⁺ by the redox-active substrates, generating spatially separated redox centres that drive tandem oxidative and reductive transformations. Comprehensive spectroscopic, microscopic, and analytical studies confirm the successful formation of the CBB/RuPS hybrid. Steady-state and time-resolved spectroscopic analyses reveal the thermodynamic viability of photoinduced electron transfer, with CBB exhibiting a sub-nanosecond photoluminescence lifetime and electron transfer to RuPS occurring within 200–300 ps. This is evidenced by the appearance of RuPS^•− signatures and multiexponential decay kinetics of CBB. Finally, the efficient exciton diffusion in the hybrid system is harnessed for in vitro photo-biocatalytic reactions, enabling selective oxidation and reduction of substrates, demonstrating potential cytotoxicity toward cancer cells via deprivation of NADH/pyruvic acid and in situ generated ROS species.