Chromium-Mediated and Ligand-Dependent Activity Engineering of Boron-Doped g-C₃N₄ Photo-oxidative Nanozymes for Breaking the pH Limitation

Howto overcome the intrinsic low activity of most oxidase andperoxidase mimics at neutral pH has been extremely challenging. Herein,we represent a chromium-mediated and ligand-dependent strategy toactivate the oxidase-like activity of boron-doped g-C3N4 (B-g-C3N4, denoted as BG), aiming atbreaking the pH limitation. Cr (III) can be in situ oxidized to Cr(IV) by generated O-& BULL;(2) (-) upon UV light irradiation, which then works as a catalysis mediatorto oxidize TMB under a neutral environment. Excitingly, the TMB oxidationcan be rationally modulated by ligands on the BG coordinating withchromium. We verify that the PEI-Cr3+ coordination outperformedCit-PEI-Cr3+ on the oxidase-like activity through a moreaccelerated electron transfer, unveiled by the Gauss theoretical calculations.This study highlights a paradigm of tuning the coordination environmenton nanozyme surface via the ligand engineering strategy for boostingthe oxidase-mimicking activity and breaking the pH limitation. Meanwhile,the catalysis-based colorimetric assay for accurate and selectiveidentification of Cr3+ was achieved.