Ordered Co-III-MOF@Co-II-MOF Heterojunction for Highly Efficient Photocatalytic Syngas Production

The design of advanced metal-organic framework (MOF) catalysts for solar-driven conversion of CO2 into syngas (CO/H-2 mixture) is beneficial. Herein, the design of a joint MOF heterostructure consisting of orderly assembled Co-II- and Co-III-based Prussian blue analogs (PBAs) driven by their spontaneous lattice match in the growth process is reported. As-prepared H/Co-III-PBA@Co-II-PBA cage is a mesocrystal and exhibits superior photocatalytic syngas production activity (V-CO up to 50.56 mmol g(-1) h(-1), CO/H-2 = 1:1), which is among the best state-of-the-art heterogeneous photocatalysts in the literature. Theoretical calculations and experimental results confirm that Co-III-PBA exerts a stronger affinity for CO2 molecules than Co-II-PBA, thus serving as the active site. The built-in electric field in the Co-III-PBA@Co-II-PBA heterojunction can direct the fast transport of photogenerated electrons from Co-II-PBA to the active Co-III-PBA. In the present case, the engineering of electronics outweighs morphological engineering to enhance the catalytic properties of Co-III-MOF@Co-II-MOF for CO2-to-syngas conversion.