Melem-derived poly(heptazine imide) for effective charge transport and photocatalytic reforming of cellulose into H2 and biochemicals under visible light

Poly(heptazine imide) (PHI) has emerged as a promising photocatalyst due to its ability to store long-lived photoelectrons. In this study, we report a structure-directed approach to synthesize potassium (K)-PHI from various allotropes of polymeric carbon nitride (PCN) for facilitating photoelectron transfer and improving H2 production under visible light. The K-PHI derived from the melem units exhibits high structural intactness and produces H2 more efficiently than the K-PHIs from other allotropes of PCN. The PCN-precursor optimization, to reduce the defect states and increase cyanamide functionalities of the K-PHI, serves as a vital factor in photoelectron extraction by Pt-cocatalyst for H2 production. Moreover, the melem-derived K-PHI steadily reforms cellulose into H2 (34 μmol h−1) and several chemicals for 6 days. The chemicals from the cellulose-reforming comprise C6 to C1 esters, acids, aldoses, aldehydes, and alcohols. The degradation from C6 to C1 proceeds sequentially by alternating hydrolysis and photocatalytic oxidation.