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

Abstract

The photochemical reduction of carbon dioxide (CO 2 ) 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-C 3 N 4 , 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-C 3 N 4 formation. Benefitting from the confinement effect of MOL matrix and the close contact between MOLs and g-C 3 N 4 precursor, the Co(II) sites can be homogeneously and atomically dispersed on the surface of g-C 3 N 4 during the process of g-C 3 N 4 formation. Impressively, this photocatalyst possesses excellent catalytic performance for photochemical CO 2 -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 CoCl 2 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. With exposed active sites orderly confined on the surface, metal-organic layers are found to be ideal metal-source precursors used to prepare g-C 3 N 4 -based single-atom photocatalysts for efficiently catalyzing CO 2 reduction. • A ligand replacement approach was developed for the large-scale production of 2D monolayer MOLs from general 3D MOFs. • The resulted 2D monolayer MOLs were used as precursors for the preparation of C 3 N 4 -based single-atom photocatalysts. • The cheap photocatalysts exhibited excellent catalytic performance for photochemical CO2 reduction. • The structure-activity relationship was investigated and revealed experimentally.