Visible Light-Driven Acetaldehyde Production from CO₂ and H₂O via Synergistic Vacancies and Atomically Dispersed Cu Sites

Acetaldehyde (CH3CHO) is of great industrial importance and serves as a key intermediate in various organic transformations. Photocatalytic production of acetaldehyde from CO2 represents a sustainable route compared to conventional oxidation processes. However, current photocatalytic systems often face challenges, including limited product selectivity and dependence on sacrificial reagents. Here, we present a Cd0.6Zn0.4S (CZS) photocatalyst co-modified with sulfur vacancies and atomically dispersed Cu (Cu/CZS-Vs) for the efficient conversion of CO2 to acetaldehyde. Charge density analysis reveals that sulfur vacancies induce charge accumulation around the adjacent metal atoms, creating active sites that strongly anchor CO2 and H+, thereby promoting CO2 conversion while suppressing the competing hydrogen evolution reaction. The atomically dispersed Cu sites facilitate the conversion of key intermediates (i.e., *CHO and *CO) to the crucial C-2 intermediate *OCCHO, which can subsequently be converted to acetaldehyde. As a result, this catalyst achieves an acetaldehyde yield of 121.5 mu mol g(-1) h(-1) with a selectivity of ca. 80 % via photocatalytic CO2 conversion in the absence of sacrificial agents, along with a quantum efficiency of ca. 0.53 % at 400 nm, underscoring its potential for practical CO2 conversion applications. These results are expected to pave the way for future developments in green chemical processes.