Amyloid-Like Protein-Modified Carbon Nitride as a Bioinspired Material for Enhanced Photocatalytic CO₂ Reduction

Modification of g-C 3 N 4 with metal-free biomaterials through an environmentally friendly, low-energy, facile, and rapid single-step method is desired for the preparation of photocatalysts with efficient activity and high selectivity of CO 2 reduction but remains a great challenge. Herein, we develop a phase-transitioned protein modification strategy for photocatalysts through superfast amyloid-like protein assembly on surfaces using a one-step sequential coating method. Metal-free carbon nitride/protein heterojunction composite photocatalysts (the phase-transitioned lysozyme (PTL), phase-transitioned bovine serum albumin (PTB), and phase-transitioned ovalbumin (PTO)-coated carbon nitride@SiO 2 (CN@SiO 2 ) and bioinspired carbon nitride hollow nanospheres (CN-HS) obtained by etching of CN@SiO 2 ) are prepared using lysozyme, bovine serum albumin, and ovalbumin. The insulator–semiconductor heterojunctions formed at the protein–carbon nitride interface promote the migration and separation of photogenerated charges. The exposed hydrophobic alkyl and aryl groups of the surface-modified protein enable the formation of a CO 2 –aqueous solution–photocatalyst three-phase interface on the catalyst surface and the exposed −NH 2 groups provide sites for CO 2 adsorption, which effectively increases CO 2 mass transfer and its adsorption as well as hydrophobicity, promoting CO 2 reduction and inhibiting hydrogen production. Therefore, protein modification effectively improves the CO 2 reduction activity and CO selectivity. For instance, compared to CN-HS, the CO yield of the PTL-modified CN-HS (1346.5 μmol g –1 ) increased by 24.5 times and the CO selectivity reached 90.5%. These findings represent a critical advancement in the surface modification of carbon nitride for CO 2 reduction and the design of bioinspired materials for various applications.