Efficient photoredox co-upcycling of CO2 and plastic waste by band-gap-engineered ZnxCd1–xS catalyst

Solar-driven CO2 reduction combined with plastic waste valorization presents a versatile approach to simultaneously reset misaligned hydrocarbon resources and achieve a carbon-neutral cycle. Herein, we demonstrate a co-upcycling heterogeneous photoredox catalysis for efficient CO2 reduction to tunable syngas, integrated with polyethylene terephthalate (PET) plastic conversion for accessing acetate, over the spherical band-gap-engineered ZnxCd1-xS catalyst. The key to steering the syngas H2/CO rate is to modulate the conduction band bottom potentials of the ZnxCd1-xS photocatalysts by altering the Zn/Cd ratio, which results in syngas H2/CO production over a wide range. Moreover, controlled variations in the molar ratio of Zn/Cd regulate the electron-hole separation capability, thereby endowing Zn0.8Cd0.2S with the optimum syngas and acetate production rates. The underlying mechanistic origin of such a redox reaction involving CO2-assisted PET plastic conversion has been systematically investigated. This win-win cooperative photoredox catalysis offers a tantalizing possibility for co-upcycling of CO2 and PET into value-added feedstocks.