Room-temperature photosynthesis of propane from CO2 with Cu single atoms on vacancy-rich TiO2

A photocatalyst for CO2 reduction to C3H8 is prepared by implanting Cu single atoms on vacancy rich TiO2 single layers. Key reaction intermediates, *CHOCO and *CH2OCOCO, are stabilized on the catalyst which promotes C-C bond formation. Photochemical conversion of CO2 into high-value C2+ products is difficult to achieve due to the energetic and mechanistic challenges in forming multiple C-C bonds. Herein, an efficient photocatalyst for the conversion of CO2 into C3H8 is prepared by implanting Cu single atoms on Ti0.91O2 atomically-thin single layers. Cu single atoms promote the formation of neighbouring oxygen vacancies (V(O)s) in Ti0.91O2 matrix. These oxygen vacancies modulate the electronic coupling interaction between Cu atoms and adjacent Ti atoms to form a unique Cu-Ti-V-O unit in Ti0.91O2 matrix. A high electron-based selectivity of 64.8% for C3H8 (product-based selectivity of 32.4%), and 86.2% for total C2+ hydrocarbons (product-based selectivity of 50.2%) are achieved. Theoretical calculations suggest that Cu-Ti-V-O unit may stabilize the key *CHOCO and *CH2OCOCO intermediates and reduce their energy levels, tuning both C-1-C-1 and C-1-C-2 couplings into thermodynamically-favourable exothermal processes. Tandem catalysis mechanism and potential reaction pathway are tentatively proposed for C3H8 formation, involving an overall (20e(-) - 20H(+)) reduction and coupling of three CO2 molecules at room temperature.