Boosting the Catalase-Like Activity of SAzymes via Facile Tuning of the Distances between Neighboring Atoms in Single-Iron Sites

A nanozyme with neighboring single-iron sites (Fe-2-SAzyme) was introduced as a bioinspired catalase mimic, featuring excellent activity under varied conditions, twice as high as that of random Fe-1-SAzyme and ultrahigh H2O2 affinity as that of bioenzymes. Surprisingly, the interatomic spacing tuning between adjacent iron sites also suppressed the competitive peroxidase pathway, remarkably increasing the catalase/peroxidase selectivity up to similar to 6 times compared to Fe-1-SAzyme. This dramatically switched the catalytic activity of Fe-SAzymes from generating (i.e. Fe-1-SAzymes, preferably mimicking peroxidase) to scavenging ROS (i.e. Fe-2-SAzymes, dominantly mimicking catalase). Theoretical and experimental investigations suggested that the pairwise single-iron sites may serve as a robust molecular tweezer to efficiently trap and decompose H2O2 into O-2, via cooperative hydrogen-bonding induced end-bridge adsorption. The versatile mechano-assisted in situ MOF capsulation strategy enabled facile access to neighboring M-2-SAzyme (M=Fe, Ir, Pt), even up to a 1000 grams scale, but with no obvious scale-up effect for both structures and performances.