Reactive Site Transformation in Non-Metal Doped Polymeric Carbon Nitride Improving CO₂ Photoreduction Efficiency

Polymeric carbon nitride (PCN, also called melon) was a potential photocatalyst for the CO₂ reduction reaction (CO₂RR), but the conjugation of the system inhibited the efficiency. By modifying melon with non-metal elements such as boron (B), phosphorus (P), oxygen (O), and sulfur (S), we found that S (or O) doped melon (S/melon, O/melon) transformed the reactive site of pyridine nitrogen (N) to carbon (C), which promoted COOH* hydrogenation to CO* and, thus, improved the CO₂ reactivity and CO selectivity significantly. In addition, nonadiabatic molecular dynamics simulations showed that the trap states of the O/melon and S/melon can rapidly capture excited electrons to participate in the CO₂RR and improve the photocatalytic reaction efficiency. This work provided theoretical insight for the design of efficient CO₂RR photocatalysts based on metal-free materials.