Revealing the activity of inert Zn-based ZIF-L/aerogel composites in Fenton-like catalysis: Electron-deficient N ([sbnd]C[dbnd]N[sbnd]C) triggering 1O2 evolution

Abstract

The inertness of Zn with fully occupied 3d10 configurations makes original Zn-based MOFs inactive, which are rarely reported in Fenton-like reactions. Herein, the prepared ZIF-L (Zn) was immobilized on foaming gelatin aerogel to fabricate composite catalysts (ZIF-L/FGA150) for PMS-based Fenton-like reactions. Unexpectedly, ZIF-L/FGA150 exhibited high Fenton-like activity in activating PMS for antibiotic norfloxacin (NOF) removal, by which over 99 % NOF could be degraded in 30 min. 1O2 was proved to be the sole contributor to mediating the non-radical oxidization process without the participation and evolution of free radicals. Mechanism investigation further revealed that the uncoordinated N (CNC) at edge 2-methylimidazole bonding with one Zn core were electron-deficient as a result of the deviation of electron density towards Zn-N4 coordination, and the electron-deficient N were identified as the active sites responsible for triggering electron transfer from the nucleophilic peroxy bonds of PMS accompanied by PMS decomposition into SO5− to generate singlet oxygen (1O2), thus driving NOF degradation. Owing to the 1O2-mediating non-radical oxidization, ZIF-L/FGA150 possessed high Fenton-like activity, unaffected by the interference of various environmental factors and in multiple actual water matrixes. This work might provide a novel insight into the reactivity of Zn-based MOFs in Fenton-like catalysis and develop an effective approach for antibiotic remediation.