Visible-light-driven CO₂ reduction to ethylene on CdS: Enabled by structural relaxation-induced intermediate dimerization and enhanced by ZIF-8 coating

Visible-light-driven CO₂ reduction yielding commodity chemicals such as ethylene holds tremendous potentials for achieving a carbon-neutral circular economy in the energy and chemical industry. Despite the success of electrochemical CO₂ reduction, efficient and selective ethylene generation has not been achieved by photocatalytic means because the intermediate dimerization fails to occur on existing photocatalysts. Here, we first demonstrate that the presence of sulfur vacancies in CdS (S_v-CdS) lead to reduced Cd-Cd distance and charge enrichment on Cd atoms. This structural relaxation and associated electronic structure tuning endow successful *CHO dimerization and hence ethylene generation. The photocatalyst can be optimized by coating S_v-CdS with ZIF-8 to form a core-shell structure, which presents further lowered energy barrier for both *CO hydrogenation and *CHO dimerization. With these combined intermediate manipulation strategies, the optimized photocatalyst exhibits a record-high ethylene selectivity of 12.8 % at a production rate of 0.8 μmol g⁻¹ h⁻¹.