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

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 Cd_0.6Zn_0.4S (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 C₂ intermediate *OCCHO, which can subsequently be converted to acetaldehyde. As a result, this catalyst achieves an acetaldehyde yield of 121.5 μmol 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.