N- and B-doped fullerene as peroxidase- and catalase-like metal-free nanozymes with pH-switchable catalytic activity: A first-principles approach

Metal-free nanozymes are designed to function as peroxidase or catalase, controllable by pH conditions. Using first-principles density functional theory (DFT) calculations, we propose that heteroatomic doping of N and B to fullerene is promising to form active sites for catalyzing oxygenate intermediates for H₂O₂ decomposition. In neutral pH with bare surfaces, both N- and B-doped fullerenes show peroxidase-like catalytic activity rather than a catalase-like one. The presence of water, at neutral pH, drives peroxidase-like catalysis on the B-doped fullerene with marginal energy, in which the B atom functions as a strong electrophile that firmly adsorbs OH* and promotes O-O chemical bond dissociation. Interestingly, acidic, and basic environments tune their selectivity toward peroxidase- and catalase-like catalytic activity, respectively, mediated by pre-adsorbed H* and OH*. The DFT calculations demonstrate the applicability of N- and B-doped fullerenes by showing significantly decreased dissociation energy barriers of H₂O₂ into 2OH during the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB). We believe that the results can provide a useful guide for designing highly active and selective carbon-based nanozymes toward H₂O₂ decomposition.