Manganese-doped nickel–iron layered double hydroxides for enhanced peroxidase, oxidase, and catalase activities

Nanozymes with multi-enzymatic activity in biomedical fields have gained significant attention. However, the effects of metal-doping elements on the structure-activity relationship of many nanomaterials remain insufficiently understood. Herein, we selected NiFe-LDH as the base material to systematically investigate how varying Mn doping ratios and specific Mn doping sites within the NiFe-LDH lattice influences peroxidase (POD), oxidase (OXD), and catalase (CAT) activities. Notably, substitution of Mn at both the Ni and Fe sites in NiFe-LDH (designated as NiFeMn-20%-C) led to markedly improved multi-enzymatic activities compared to Mn substitution at only the Fe site (NiFeMn-20%). To elucidate the mechanisms underlying these enhancements, density functional theory calculations are employed to assess the Gibbs free energies associated with various enzymatic reaction intermediates at the two classes of Mn active sites. These results indicate that the Mn sites in NiFeMn-20%-C are more favorable for promoting the redox conversion of H₂O₂ and O₂ than those in NiFeMn-20%. Our results underscore the critical importance of carefully selecting appropriate metal substitution sites in the design of LDH-based materials to achieve enhanced multi-enzymatic activity.