Single-atom engineering of metal-organic frameworks toward healthcare

Single-atomic nanocatalysts/nanozymes (SACs/SAEs) have emerged as a research frontier on account of the maximum atom-utilization efficiency and well-defined localized structure. Metal-organic frameworks (MOFs) featuring structural diversity and functional tunability are promising host materials in constructing SACs/SAEs. Further, pyrolysis of MOF precursors under certain conditions can lead to the formations of MOF-derived SACs/SAEs. In this review, we first introduce the classification and enzymatic mechanisms of nanozymes, comprehensive characterization techniques for SACs/SAEs, and various synthetic methodologies of MOF-based SACs/SAEs. Next, we highlight the recent advances of MOF-based SACs/SAEs in the enzymatic healthcare area, i.e., cancer treatment, biosensing, antibacterial approaches, reactive oxygen species scavenging, and environmental protection. Finally, we summarize the insights we gain from these studies and discuss possible design principles and future challenges for a deeper understanding of this emerging field, thus offering great opportunities to leap over conventional nanozymes into a new era of next-generation biosafe SACs/SAEs.