Metallothionein‐Inspired Asymmetric Heteroatom Doping of Single‐Atom Nanozymes for Multi‐Enzyme Biocatalysis

Abstract Single‐atom catalysts (SACs) exhibit enzyme‐mimicking activity but are often limited by single‐enzyme–like functions and modest catalytic efficiency. Here, a metallothionein‐inspired heteroatom doping strategy is reported to construct asymmetric Fe single‐atom catalysts (FeN ₃ S). Fe ³ ⁺ is coordinated with cysteine via strong mercaptide bond formation, followed by zeolitic imidazolate framework‐8 (ZIF‐8) biomineralization and pyrolysis. The FeN ₃ S catalyst displays markedly enhanced multi‐enzyme activities—including NADH oxidase‐, oxidase‐, peroxidase‐, and catalase‐like activities—with 1.35–4.60‐fold improvements compared to sulfur (S)‐free analogues. This high multi‐enzyme efficiency arises from i) atomically dispersed Fe from biomineralization; ii) the large surface area and pore volume retained from the original metal–organic framework, and iii) the S‐doping achieved through the strong mercaptide coordination between Fe and S. The S doping not only tunes electronic structure of Fe single atom to reduce activation barriers and enhances substrate interaction, but also facilitates charge transfer. As a result, FeN ₃ S induces ≈90% tumor cell suppression within one day through reactive oxygen species generation and disruption of the NADH/NAD⁺ balance, highlighting its strong potential for cancer therapy. This work provides a bioinspired strategy for advancing SACs toward multifunctional biocatalysis and biomedical applications.