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. The bimetallic CoTi-MOF@half-metallic C(CN) 3 tandem catalytic system effectively facilitates photocatalytic C-C coupling. The CO generation on C(CN) 3 diffuses to the CoTi-MOF, where the bimetallic Co-Ti sites facilitate the coupling of *CO and *CHOH intermediates, thereby promoting the formation of C 2 H 4 during photocatalytic CO 2 reduction. • A novel bimetallic CoTi-MOF@metal-free C(CN) 3 tandem catalyst has been prepared. • The intermediate *CO and bimetallic Co/Ti sites commonly promote C-C coupling. • The CoTi-CN tandem system sensibly improved the yield and selectivity of C 2 H 4 . • The *CO and Co/Ti sites reduce the energy barrier for the rate-determining step (RDS) of C 2 H 4 production.