Quasi-homogeneous heterojunction of CdSe quantum dots and a cobalt porphyrin for efficient Visible-Light-Driven CO₂...

Photoreduction of CO₂ into chemical fuels presents an attractive route to mitigate the depletion of fossil fuels and relieve the greenhouse effect. Molecular catalyst-based organic-inorganic heterojunctions typically demonstrate superior photocatalytic performance by inhibiting the recombination of photogenerated carriers and providing active sites. However, most of these heterojunctions are based on immobilizing molecular catalysts on solid bulk structured semiconductors, which suffer from mass transfer and diffusion limitations. Herein, we developed a highly efficient quasi-homogeneous heterojunction of CdSe@CoTMPyP consisting of water-soluble cobalt porphyrin ([5,10,15,20-(tetra-N-methyl-4-pyridyl)porphyrin-cobalt], CoTMPyP) with CdSe quantum dots (QDs) through electrostatic self-assembly strategy. Compared with CdSe QDs-based photocatalysts, the optimized CdSe@CoTMPyP exhibited a record high PCR efficiency with a CO evolution rate of 4.3 mmol g^-1h^-1 and a turnover number (TON) of 31, 287 in a fully aqueous media. Time-resolved photoluminescence (TRPL) and femtosecond transient absorption (fs-TA) spectroscopy were employed to elucidate the interfacial electron transfer dynamics. Furthermore, density functional theory (DFT) calculations reveal a facilitated electron transfer pathway and a significantly reduced energy barrier for COOH* formation in the heterojunction. This study presents a strategy for the synthesis of quasi-homogeneous heterojunctions of organic molecular catalysts and inorganic semiconductors, providing valuable insights for designing molecular heterogeneous photocatalysts for efficient solar fuel generation.