Hg-enhanced oxidase-like activity of platinum nanoparticles immobilized on porphyrin-based porous organic polymer for the colorimetric detection and removal of Hg.

Porphyrin-based porous organic polymer (POP) with uniformly immobilized platinum nanoparticles (Pt NPs) were designed and synthesized, and it was demonstrated that such nanocomposites (Pt/POP) have oxidase-like activity. Surprisingly, Hg significantly enhanced the oxidase-like activity of Pt/POP. The enhancement was attributed to the capture of Hg by the thioether group in Pt/POP and the subsequent redox reaction of Hg with Pt NPs, accelerating the electron transfer. In the presence of Hg, Pt/POP catalyzed the colorless 3,3',5,5'-tetramethylbenzidine (TMB) to turn blue rapidly and changed its absorbance at 652 nm. Based on this, a fast-response colorimetric sensor was constructed for the sensitive detection of Hg with a linear range of 0.2-50 μM and a detection limit of 36.5 nM. Importantly, Pt/POP can be used as an adsorbent for the efficient removal of Hg with a removal efficiency as high as 99.4%. This work provides a valuable strategy for colorimetric detection and efficient removal of Hg.