Structure–activity relationship in Cu-based coordination polymers for efficient photocatalytic degradation of antibiotics

The rapid emergence of antibiotic contaminants in aquatic environments poses a serious threat to ecological and human health, necessitating the development of efficient and sustainable remediation strategies. In this context, Cu-based coordination polymers (Cu-CPs) have attracted considerable attention due to their tunable structures and promising photocatalytic properties. Herein, two new Cu(II)-based CPs, namely {[Cu2(L)(μ3-OH)(bid)0.5(H2O)]·H2O}n (1), and [Cu(HL)(bip)·H2O]n (2) (H3L = 5-(4′-carboxyphenoxy) isophthalic acid, bid = 1,4-bis (1-imidazoly) −2,5-dimethy lbenzene, bip = 3,5-bis(1-imidazolyl) pyridine), were synthesized and comprehensively characterized by FTIR, TGA, PXRD, and single-crystal X-ray diffraction analyses. The photocatalytic activities of these Cu-CPs were evaluated toward the degradation of selected antibiotics, including tinidazole (TDZ), sulfadiazine (SDZ), sulfasalazine (SLA), ornidazole (ODZ), and tetracycline (TCY), under light irradiation. Among them, CP (1) exhibited superior performance, achieving 85.37% degradation of TCY (40 ppm) within 65 min using only 5 mg of catalyst, while negligible degradation in the dark confirms the photocatalytic nature of the process. Mechanistic studies indicate that upon light irradiation, photogenerated electron–hole pairs facilitate the formation of superoxide radicals (•O2−), which act as the primary active species in pollutant degradation. Furthermore, the catalyst demonstrates good stability, recyclability, and efficiency in aqueous media. This work highlights the potential of rationally designed Cu-CPs as effective photocatalysts for environmental remediation.