Facile strategy to prepare a metalloporphyrin-based hydrophilic porous organic polymer with enhanced peroxidase-like activity and high stability for colorimetric detection of H2O2 and glucose

Nanozymes, nanomaterial-based artificial enzymes, have attracted researchers' enormous interest due to their unique properties compared with natural enzymes. To mimic the catalytic function of natural enzymes, designing high-efficient, novel nanozymes is crucial yet challenging task. In this article, we described the synthesis and functions of a metalloporphyrin-based porous organic polymer, namely FePPOPs-SO3H. FePPOPs-SO3H was synthesized effortlessly via an extensive aromatic electrophilic substitution and the following sulfonation reactions. This strategy was cost-efficient without the participation of precious metal catalysts. The resultant FePPOPs-SO3H is intriguing since the framework itself is constructed by covalently linked porphyrin units, which could serve as a built-in catalyst and strengthen the stability of polymer. With sulfonic acid side groups, FePPOPs-SO3H is well water-dispersive. Owing to these unique characteristics, FePPOPs-SO3H exhibited excellent peroxidase-like activity toward a classical peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) to produce a blue product only within 20 s. The peroxidase-mimicking performance of FePPOPs-SO3H outperforms the ferric porphyrin monomer and normal Fe3O4 nanoparticles. Based on the excellent catalytic activity of FePPOPs-SO3H, two visual colorimetric sensors for ultrafast detecting H2O2 and glucose, respectively, were constructed with a wide linear range of 50-1800 mu M (for H2O2) and 200-1500 mu M (for glucose), as well as a relative lower limit of detection (LOD) [26.70 mu M (for H2O2) and 16.38 mu M (for glucose)]. Our strategy highlights opportunities for the design of new metalloporphyrin-based porous organic polymers with built-in catalytic skeletons and inherently excellent peroxidase-mimicking performance.