Cyano-modified potassium-sodium poly(Heptazine Imide) nanosheets for photocatalytic hydrogen peroxide reduction coupled with 5-hydroxymethylfurfural oxidation

The efficacy of poly(heptazinonimide) (PHI) materials in photocatalytic applications is often constrained by limited visible light absorption and charge separation. In this study, we successfully synthesized cyano-modified potassium-sodium poly(heptazinonimide) (KNPHI) nanosheets using a molten salt method, which significantly enhances photocatalytic performance. The resulting KNPHI nanosheets achieve hydrogen peroxide (H2O2) concentrations up to 8.64 mM, nearly 1.9 and 123 times greater than that achieved by KPHI and PCN respectively. Notably, integrating cyano groups and potassium-sodium ions within KNPHI enhances visible light absorption, intermediate adsorption and charge separation, as confirmed by experimental characterizations and DFT calculations, thereby improving the oxygen reduction reaction efficiency. Furthermore, the use of KNPHI for 5-hydroxymethylfurfural oxidation, coupled with oxygen reduction reaction pathway, was systematically investigated. These findings offer promising avenues for the development of advanced photocatalysts that support sustainable energy production and green chemical synthesis.