Potassium-promoted coupling of photochemical and thermochemical pathways in solar driven C2+ synthesis

Potassium is extensively recognized as an effective catalyst promoter in thermocatalytic CO2 hydrogenation, however, its involvement in photothermal catalytic systems, and, more importantly, its working mechanism, remains largely unexplored. Herein, a series of MOF-derived CoFeZn catalysts with systematically varied potassium contents were synthesized to elucidate the role of potassium in photothermal catalytic CO2 hydrogenation. Advanced in situ characterizations, particularly a customized mass spectrometry (MS) setup, reveal that potassium synergistically couples with light irradiation to simultaneously enhance CO2 activation, suppress excessive hydrogenation, and modulate the kinetics and spatial distribution of photo-excited hot electrons, thereby shifting the reaction from thermally strong hydrogenation to thermally-photochemically regulated C–C coupling pathways. Optimization of potassium promoter achieved an impressive C2–C4 hydrocarbon production rate of 2.26 mmol·g−1·h−1 in a flow-type reactor, nearly a twofold enhancement compared with the dark reaction and 1.74 times that of promoter-free catalyst, while maintaining excellent stability. This study unveils a synergistic interaction between potassium and light, establishing potassium as a multifunctional promoter for pathway-selective, solar-driven hydrocarbon production from CO2.