Photocatalytic conversion of CO₂ to C₂₊ products such as ethylene are a promising route to the goal of carbon neutrality, but remain a major challenge due to the high activation barrier for CO₂ and similar reduction potentials of many possible multielectron transfer products. In a study published in Journal of the American Chemical Society, a research group led by Professor Cao Rong and Prof. Huang Yuanbiao of the Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences reported a tandem photocatalysis strategy to promote CO conversion₂ to ethylene. The researchers developed this tandem photocatalysis strategy by constructing synergistic dual sites in rhenium-(I) bipyridine fac-[Re^Me(BPY) (SK)₃Cl] (Re-bpy) and a copper porphyrin triazine framework (PTF(Cu)). With these two catalysts, they produced a large amount of ethylene at a rate of 73.2 μmol g^-1 h^-1 under visible light irradiation. Ethylene cannot be obtained from CO₂ using any component of Re-bpy or PTF(Cu). Only the monocarbon product CO is produced under similar conditions with a single catalyst. In the tandem photocatalytic system, the researchers found that CO generated at Re-bpy sites was adsorbed by nearby single Cu sites in PTF(Cu), followed by a synergistic CC coupling process that ultimately produces ethylene. Based on in situ Fourier transform infrared spectroscopy (DRIFTS) analysis of the spectrum and density functional theory (DFT) calculations, the researchers photoreduced CO₂ to Re-bpy-CO * above Re-bpy, from which part of the CO can be desorbed and transferred to nearby PTF(Cu), where it is adsorbed by a monoatomic Cu site to form PTF(Cu)-CO*. In addition, CC coupling occurred in synergy between PTF(Cu)-CO* and Re-bpy-CO* intermediates to form Re-*CO-CO*-Cu, which was finally reduced and released as ethylene with multistep electron transfer processes coupled with by protons (PCET). DFT calculations showed that the coupling process between PTF(Cu)-*CO and Re-bpy-*CO to form the key intermediate Re-bpy-*CO-*CO-PTF(Cu) is vital for C₂H₄ production. This study provides a new way to design efficient photocatalysts for CO photoconversion₂ to C₂ products through a tandem process driven by visible light under mild conditions (Liou Jia, Chinese Academy of Sciences).