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

Modification of g-C₃N₄ 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 CO₂ 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@SiO₂ (CN@SiO₂) and bioinspired carbon nitride hollow nanospheres (CN-HS) obtained by etching of CN@SiO₂) 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 CO₂-aqueous solution-photocatalyst three-phase interface on the catalyst surface and the exposed -NH₂ groups provide sites for CO₂ adsorption, which effectively increases CO₂ mass transfer and its adsorption as well as hydrophobicity, promoting CO₂ reduction and inhibiting hydrogen production. Therefore, protein modification effectively improves the CO₂ 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 CO₂ reduction and the design of bioinspired materials for various applications.