Highly Dispersive Ni@C and Co@C Nanoparticles Derived from Metal-Organic Monolayers for Enhanced Photocatalytic CO2 Reduction.

The metal/carbon composites prepared by direct pyrolysis of metal-organic frameworks (MOFs) are regarded as ideal catalysts. However, conventional MOFs show a three-dimensional bulk structure. For bulk MOF-derived catalysts, most active metal sites are confined in the interior and not fully utilized. In this work, metal-organic monolayers (MOLs) are used as the starting precursors to prepare carbon-wrapped metal nanoparticles, which are further employed as catalysts for photocatalytic CO2 reduction. The as-prepared Ni-MOLs and Co-MOLs have an ultrathin thickness of ∼1 nm. It is interestingly found that their derived Ni@C and Co@C nanoparticles are highly dispersive and connected with each other like a piece of paper. As compared with bulk MOF-derived counterparts, MOL-derived catalysts increase the accessibility of active metal sites, which can accelerate electron transfer from photosensitizers to Ni@C and Co@C nanoparticles. In this way, the catalytic activity can be greatly improved. Besides, the magnetic nature of Ni@C and Co@C nanoparticles enables the easy separation and recycling of catalysts. It is expected that this work will provide instructive guidelines for the rational design of MOL-derived catalysts.