Facile preparation of porous carbon nitride for visible light photocatalytic reduction and oxidation applications

In this work, we have employed melamine, cyanuric acid and thymine to fabricate triazine-based carbon nitrides (CNs) by supramolecular approach. The resultant CNs possess large specific surface area, hierarchical porous structure, better light absorption capacity and high separation rate of photoinduced carriers. Then, the photocatalytic reduction and oxidation performance has been evaluated. The obtained CNs exhibit enhanced photocatalytic reduction performance on water splitting to H₂, the largest hydrogen evolution rate can reach 8466.3 μmol g⁻¹ h⁻¹, which is 81.9 times as high as that of bulk CN. Simultaneously, the porous CNs show excellent photocatalytic reduction ability on the conversion of CO₂ to H₂, CO and CH₄. Of particular interest is that they have high selectivity for CO. It's worth noting that the porous CNs also possess outstanding photocatalytic oxidation ability on high concentration nitric oxide (NO), and the highest NO conversion rate can reach 79.3% under visible light. The enhanced photocatalytic performance for the multifunctional porous CN can be ascribed to the synergic effect of large specific surface area, strong light absorption capacity and fast separation of photoinduced electron–hole pairs. Finally, the photocatalytic reduction and oxidation mechanism of the porous CN is also proposed and discussed.