Amyloid-Like Protein-Modified\nCarbon Nitride as a\nBioinspired Material for Enhanced Photocatalytic CO<sub>2</sub> Reduction

Modification of g-C<sub>3</sub>N<sub>4</sub> with metal-free\nbiomaterials\nthrough an environmentally friendly, low-energy, facile, and rapid\nsingle-step method is desired for the preparation of photocatalysts\nwith efficient activity and high selectivity of CO<sub>2</sub> reduction\nbut remains a great challenge. Herein, we develop a phase-transitioned\nprotein modification strategy for photocatalysts through superfast\namyloid-like protein assembly on surfaces using a one-step sequential\ncoating method. Metal-free carbon nitride/protein heterojunction composite\nphotocatalysts (the phase-transitioned lysozyme (PTL), phase-transitioned\nbovine serum albumin (PTB), and phase-transitioned ovalbumin (PTO)-coated\ncarbon nitride@SiO<sub>2</sub> (CN@SiO<sub>2</sub>) and bioinspired\ncarbon nitride hollow nanospheres (CN-HS) obtained by etching of CN@SiO<sub>2</sub>) are prepared using lysozyme, bovine serum albumin, and ovalbumin.\nThe insulator–semiconductor heterojunctions formed at the protein–carbon\nnitride interface promote the migration and separation of photogenerated\ncharges. The exposed hydrophobic alkyl and aryl groups of the surface-modified\nprotein enable the formation of a CO<sub>2</sub>–aqueous solution–photocatalyst\nthree-phase interface on the catalyst surface and the exposed −NH<sub>2</sub> groups provide sites for CO<sub>2</sub> adsorption, which\neffectively increases CO<sub>2</sub> mass transfer and its adsorption\nas well as hydrophobicity, promoting CO<sub>2</sub> reduction and\ninhibiting hydrogen production. Therefore, protein modification effectively\nimproves the CO<sub>2</sub> reduction activity and CO selectivity.\nFor instance, compared to CN-HS, the CO yield of the PTL-modified\nCN-HS (1346.5 μmol g<sup>–1</sup>) increased by 24.5\ntimes and the CO selectivity reached 90.5%. These findings represent\na critical advancement in the surface modification of carbon nitride\nfor CO<sub>2</sub> reduction and the design of bioinspired materials\nfor various applications.