Ultrafine Cu nanoparticles confined in a {Co20} thiacalix[4]arene coordination cage for efficient pollutant degradation in water

A polyhedral coordination cage (PCC) was constructed as a confined nanoreactor. • Ultrafine Cu nanoparticles of approximately 1 nm were uniformly stabilized in PCC. • Cu NPs@PCC achieved 99.09% metronidazole removal within 15 min. • PMS activation involved synergistic radical and nonradical oxidation pathways. • The catalyst showed good stability, recyclability, and broad pollutant applicability. Developing PMS-based heterogeneous catalysts with high activity and durability is limited by the aggregation and deactivation of active metal species. Herein, a cobalt-based thiacalix[4]arene polyhedral coordination cage (PCC, compound 1) was constructed as a confined nanoreactor for stabilizing ultrasmall Cu nanoparticles, yielding a Cu NPs@1 catalyst for PMS activation. The abundant exposed nitrogen-donor sites within the PCC enabled uniform confinement of ∼1 nm Cu nanoparticles and effectively suppressed their aggregation. Benefiting from the confined catalytic environment and highly dispersed active sites, Cu NPs@1 exhibited excellent activity toward metronidazole (MTZ) degradation, achieving 99.09% removal within 15 min ( k obs = 0.27 min -1 ). The catalyst maintained high performance under various pollutant concentrations, coexisting ions, and repeated cycles, and also efficiently degraded rhodamine B and tetracycline. Mechanistic studies revealed that PMS activation involved both radical and nonradical pathways, with 1 O 2 , ·OH, ·SO 4 - , and ·O 2 - contributing to pollutant oxidation. LC-MS analysis revealed that MTZ underwent hydroxylation, bond cleavage, and ring-opening reactions, leading to progressive degradation and mineralization. This work provides a coordination cage confinement strategy for constructing highly dispersed metal nanoparticle catalysts toward advanced oxidation processes. A cobalt-based thiacalix[4]arene polyhedral coordination cage (PCC) was employed as a confined nanoreactor to stabilize ultrasmall Cu nanoparticles for efficient PMS activation. The resulting Cu NPs@PCC catalyst enabled rapid metronidazole degradation through synergistic radical and nonradical pathways involving 1 O 2 , ·OH, ·SO 4 ⁻, and ·O 2 ⁻. The coordination-cage confinement effectively suppressed nanoparticle aggregation, enhanced catalytic stability, and provided a versatile strategy for advanced oxidation catalysis. Download: Download high-res image (355KB) Download: Download full-size image