Metal-free C(CN)3 cooperated with Co-Ti dual sites in bimetallic CoTi-MOF as a tandem photocatalyst for highly efficient C2H4 production

The photocatalytic reduction of carbon dioxide (CO 2 ) into high-value C 2+ hydrocarbons represents a sustainable pathway to alleviate energy shortages and reduce atmospheric CO 2 levels. In this study, a unique tandem photocatalyst (CoTi-CN), is constructed by integrating bimetallic CoTi-MOF with metal-free half-metallic C(CN) 3 . This composite demonstrates markedly enhanced activity and selectivity in the photocatalytic CO 2 reduction to ethylene (C 2 H 4 ), achieving a C 2 H 4 selectivity of 36.8% and a generation yield of 31.3 μmol g −1 over 5 h. Density functional theory (DFT) calculations combined with in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis reveal that C(CN) 3 acts as an efficient CO 2 to CO converter, while CoTi-MOF favors the adsorption and C-C coupling of *CO intermediates. The spatially decoupled CO generation and C-C coupling processes lead to optimized intermediate coverage and reduced energy barriers, resulting in superior selectivity toward multi-carbon products. This work opens new horizons for the design of tandem photocatalysts that combine half-metallic catalysts with bimetallic MOFs, achieving a significant enhancement in the activity and selectivity of photocatalytic C 2 H 4 production.