Design and Application of Imidazole-Based Hyper-Crosslinked Polymer-Stabilized Silver Nanoclusters for Wastewater Treatment

Abstract

Stabilizing metal nanoclusters in porous organic frameworks while maintaining accessible mass-transfer pathways is essential for maximizing metal-site utilization in heterogeneous catalysis. Herein, we developed a clotrimazole-derived imidazole hyper-crosslinked polymer, HCP-C, as a structurally and electronically tailored scaffold for immobilizing Ag nanoclusters. Clotrimazole serves as a multifunctional building block that combines abundant aromatic sites for hyper-crosslinking, Ag-coordinating imidazole N atoms, a polarizable N/π-electron-rich heteroaromatic environment, and bulky steric protection. By regulating the FeCl₃/DPX ratio, the pore structure and pore size distribution of HCP-C were systematically tuned, enabling a balance between Ag confinement and reactant diffusion. The optimized HCP-C framework enabled the uniform stabilization of Ag nanoclusters mainly in the range of 1−2 nm. Systematic control experiments and catalytic optimization confirmed that the activity was governed by the combined effects of Ag dispersion, Ag-site accessibility, pore-assisted mass transfer, and molecular stabilization rather than Ag loading alone. The optimized HCP-C-6-1 catalyst efficiently promoted the degradation of three representative organic pollutants, sunset yellow, phenol red, and 4-nitrophenol, at 15 °C, affording apparent rate constants of 1.567, 0.118, and 0.911 min⁻¹, respectively. It also exhibited a low activation energy of 35.985 kJ·mol⁻¹ and retained more than 99.7% sunset yellow removal after seven consecutive cycles. This work highlights clotrimazole-derived HCPs as readily accessible porous microenvironments for stabilizing and electronically regulating Ag active sites, offering a versatile platform for low-metal-consumption and energy-efficient catalytic degradation of diverse organic pollutants.