Sacrificial agent-free photocatalytic CO reduction using a 2D cobalt porphyrin-based MOF/graphene heterojunction

2D MOFs show great potential in photocatalysis owing to their ultrathin thickness, large surface area and highly accessible active sites. Nevertheless, studies applying 2D MOFs as photocatalysts are very limited, especially for photocatalytic CO 2 reduction. In this paper, a novel 2D/2D Co-PMOF/GR heterojunction was successfully constructed by coupling a 2D cobalt porphyrin-based MOF (Co-PMOF) and graphene (GR). The resultant Co-PMOF/GR composites could efficiently reduce CO 2 to CO and CH 4 under visible-light illumination without any assistance of a sacrificial agent and photosensitizer. When the content of GR was 10 wt%, the Co-PMOF/GR composite presented an optimum catalytic performance. The maximum yields of CO and CH 4 over the Co-PMOF/GR composite reached 20.25 and 1.61 μmol g −1 h −1 , respectively, which were 2.84 and 2.44 times those over pristine Co-PMOF. The enhanced catalytic efficiency was due to the synergy of higher light harvesting, enhanced CO 2 absorption and efficient charge migration within the conductive and intimate 2D heterostructure. This study offers a new idea for the fabrication of highly active 2D MOF-based photocatalysts for solar energy conversion. A 2D/2D Co-PMOF/graphene heterojunction demonstrates excellent performance towards CO 2 reduction under visible-light illumination without any assistance of a sacrificial agent and photosensitizer.