Metal-organic layers as a platform for developing single-atom catalysts for photochemical CO2 reduction

The photochemical reduction of carbon dioxide (CO2) into valuable chemicals or feedstock is very meaningful for environmental and energy sustainability. Development of efficient, robust and low-cost catalysts is necessary and desirable for their practical application. In this communication, we exploited such a catalyst by anchoring single-Co(II) sites on g-C3N4, which was firstly achieved by the pyrolysis of ultrathin cobalt metal-organic framework (MOF) nanosheets (also called metal-organic layers; MOLs) during the process of g-C3N4 formation. Benefitting from the confinement effect of MOL matrix and the close contact between MOLs and g-C3N4 precursor, the Co(II) sites can be homogeneously and atomically dispersed on the surface of g-C3N4 during the process of g-C3N4 formation. Impressively, this photocatalyst possesses excellent catalytic performance for photochemical CO2-to-CO conversion, with the CO evolution rate as high as 464.1 μmol g−1 h−1, 3 and 222 times higher than those of using bulky Co-MOF and CoCl2 as the cobalt sources, respectively. This work paves a new way to develop the cost-effective photocatalysts containing single-atom sites for clean energy production.