The engineering design of single-site nanozyme based on metal-organic layers for the detection of antioxidant substances

Nanozyme is a kind of nanomaterial with enzyme activity similar to that of a natural enzyme. In order to endow nanozymes with high catalytic efficiency, reducing the dimensionality of nanomaterials, which means more active sites of nanozymes can be exposed, is an effective way. Herein, as a kind of ultra-thin metal organic framework, metal organic layers (MOLs) based on Zr4+ and 4'-(4-carboxyphenyl)-[2,2':6′,2″-terpyridine]-5,5″-dicarboxylic acid (TPY) were selected for the construction of a single-site nanozyme. To achieve higher catalytic efficiency, single-site structure, which featured with “Fe–N–C,” was designed intelligently through coordination between Fe2+ and TPY. The as-prepared nanozyme Fe–Zr–MOL with just 2.7 wt% Fe showed high peroxidase-like activity. What's more, Fe–Zr–MOL showed excellent detection ability of ascorbic acid (AA) through colorimetric method based on the redox of oxidated 3,3′,5,5′-tetramethylbenzidine. In particular, owing to the temperature-dependent mimic enzyme activity of Fe–Zr–MOL, linear discriminant analysis method could be well used to distinguish different antioxidant substances. This work not only provides a nanozyme with high catalytic efficiency by single-site engineering based on MOL, but also realizes the sensitive colorimetric detection of AA and the differentiation of different antioxidant substances.