Nitrogen-deficient Carbon Nitride Photocatalyst for Selective Oxidation of HMF Coupled with Hydrogen Evolution

Two-dimensional polymeric carbon nitrides composed of earth-abundant elements have been known to be the potential visible-light-driven photocatalysts for solar energy conversion and environmental remediation. Intrinsic defect engineering in carbon nitrides has drawn substantial attention because it provides a promising approach to boost the photocatalytic performance of carbon nitrides without introducing heteroatom in the basic unit. In this work, melon-based carbon nitrides are prepared by thermal polycondensation of supramolecular complexes of various nitrogen-rich organic compounds. Solid-state nuclear magnetic resonance characterizations reveal that defect-modified carbon nitride can be obtained by varying the composition of supramolecular complexes. Nitrogen-deficient carbon nitride is produced by thermal polycondensation of the supramolecular complex of melamine, cyanuric acid, and triaminopyrimidine. The nitrogen-deficient carbon nitride with the exceptional photocatalytic performance for simultaneous biomass valorization and H₂ evolution compared to the pristine melon carbon nitride is demonstrated in this work. The simultaneous H₂ evolution from water splitting coupled with selective oxidation of 5-(hydroxymethyl) furfural (HMF) to 2,5-diformylfuran (DFF) is achieved over the nitrogen-deficient carbon nitride photocatalyst with activities of 70 mmol g^-1 h^-1 and 94 mmol g^-1 h^-1 under AM 1.5G (100 mWcm^-2) illumination with a UV filter. The photophysical properties of carbon nitrides are tunable by modifying the microstructure towards efficient photocatalytic activities. The influences of chemical and electronic structures on the photocatalytic activity of nitrogen-deficient carbon nitride will be discussed in this presentation.