Hierarchical Porous Carbon Nitride-Crumpled Nanosheet-Embedded Copper Single Atoms: An Efficient Catalyst for Carbon Monoxide Oxidation.

Rational design of metal single-site embedded porous graphitic carbon nitride (P-g-CN) nanostructures exploiting maximum atom utilization is warranted to enhance the thermal CO oxidation (CO) reaction. Herein, a facile, green, one-pot, and template-free approach is developed to fabricate the hierarchical porous P-g-CN-crumpled ultrathin nanosheets atomically doped with copper single atoms (Cu-P-g-CN). Mechanistically, the quick protonation of melamine and pyridine under acidic conditions induces deamination to form melem, which is polycondensed under heating. The interconnected pores, high surface area (240 mg), and maximized exposed isolated Cu atomic active sites (1.8 wt %) coordinated with nitrogen atom P-g-CN are the salient features of Cu- P-g-CN that endowed complete conversion to CO at 184 °C. In contrast, P-g-CN only converted 3.8% of CO even at 350 °C, implying the electronic effect of Cu single atoms. The abundant Cu-nitrogen moieties can drastically weaken the binding affinity of the CO-oxidation (CO) intermediates and products, thus accelerating the reaction kinetics at a low temperature. This study may promote the fabrication of P-g-CN doped with various single atoms for the oxidation of CO.