Spin Polarization-Induced Facile Dioxygen Activation in Boron-Doped Graphitic Carbon Nitride.

Dioxygen (O) activation is a vital step in many oxidation reactions, and a graphitic carbon nitride (g-CN) sheet is known as a famous semiconductor catalytic material. Here, we report that the atomic boron (B)-doped g-CN (B/g-CN) can be used as a highly efficient catalyst for O activation. Our first-principles results show that O can be easily chemisorbed at the B site and thus can be highly activated, featured by an elongated O-O bond (∼1.52 Å). Interestingly, the O-O cleavage is almost barrier free at room temperatures, independent of the doping concentration. It is revealed that the B atom can induce considerable spin polarization on B/g-CN, which accounts for O activation. The doping concentration determines the coupling configuration of net-spin and thus the magnitude of the magnetism. However, the distribution of net-spin at the active site is independent of the doping concentration, giving rise to the doping concentration-independent catalytic capacity. The unique monolayer geometry and the existing multiple active sites may facilitate the adsorption and activation of O from two sides, and the newly generated surface oxygen-containing groups can catalyze the oxidation coupling of methane to ethane. The present findings pave a new way to design g-CN-based metal-free catalysts for oxidation reactions.