Photoconversion of anthropogenic CO2 into tunable syngas over industrial wastes derived metal-organic frameworks

Abstract Industrial wastes such as electroplating sludges and anthropogenic CO2, are misplaced resources whose utilization is severely hampered by their complex compositions or low concentration. Herein, on the basis of the specific binding characteristic of metal ions with small molecules, we demonstrate gradient-upcycling of solid wastes into different metal-organic frameworks (MOFs) for anthropogenic CO2-to-syngas photoconversion. In low-concentration CO2 (10%), the as-prepared Ni MOFs exhibits record-high performance for CO2-to-CO photoconversion, while Fe MOFs favors for H2 production. By taking Fe/Ni MOFs as the modular catalysts and adjusting their ratio, syngas with a widely tunable CO/H2 ratio (1:15-14:1) was produced from CO2 photoreduction. The diverse catalytic performance of Fe/Ni MOFs originates from the different affinities towards CO2/H2O, which relates to the 3d electron numbers of metal ions. We further confirm the universality of the gradient recovery approach to upcycle metal resources from solid wastes and the modular catalysts design approach for CO2-to-syngas photoconversion.