Template-Free Synthesis of Mesoporous Fe-ZnO (TEA) via Triethylamine-Regulated Pores With Enhanced Peroxidase-Like Activity for Sensitive Detection of Sulfide Ion

Mesoporous materials have demonstrated ext- ensive application potential in adsorption, catalysis, and sensing due to their unique porous structures. However, their synthesis typically relies on templating techniques, which involve intricate processes for the removal of templates. In this study, a template-free synthesis strategy was proposed to successfully prepare mesoporous x%Fe-ZnO [triethylamine (TEA)] nanozyme with an average pore diameter of 14 nm through high-temperature activation of metal-organic framework (MOFs) precursors. TEA served as a key factor in regulating the pore size of x%Fe-ZnO (TEA). By adjusting the concentration of TEA, the particle size and pore size of the MOFs precurs could be precisely controlled, thereby achieving the formation of mesoporous structures during the high-temperature activation process of MOFs. The regulatory role of TEA was attributed to its function as a base that reacted with acidic ligands to promote ligand deprotonation, which aided in the rapid formation and growth of MOFs nuclei, thus controlling the particle size and pore size of MOFs. The 5%Fe-ZnO (TEA) catalyst exhibited optimal peroxidase-like activity due to the abundant Fe active sites and mesoporous structure, making it suitable for constructing a highly sensitive colorimetric sensor for detecting toxic and ecologically harmful sulfides ( $S^{{2}-}$ ) in environmental water samples. The sensor had a detection limit for $S^{{2}-}$ as low as 500 nM, which was below the World Health Organization limit of $15~\mu $ M, demonstrating significant potential in environmental monitoring. The results of this study emphasized the controllable preparation of mesoporous structured metal oxides through a template-free synthesis strategy, opening up new avenues in the preparation of mesoporous structured nanomaterials.