Construction of ZIF-8 Derived ZnO/Zn0.5Cd0.5S heterojunctions and their enhanced photocatalytic degradation performance towards ciprofloxacin

MOF-derived ZnO/ZCS heterojunction for CIP degradation. • Quasi-Type-I alignment overcome by interfacial built-in electric field. • 94.66% CIP removal under visible light in 120 min. • Singlet oxygen identified as dominant reactive species. • Stable performance in tap water and surface water. Ciprofloxacin (CIP) resists biodegradation and accumulates in aquatic environments, threatening ecosystems and human health. Herein, a ZIF-8-derived ZnO/Zn 0.5 Cd 0.5 S (ZnO/ZCS) heterojunction photocatalyst was fabricated via a hydrothermal-calcination method. The composite inherits a high specific surface area of 36.05 m 2 ·g –1 from the MOF precursor, while the loaded Zn 0.5 Cd 0.5 S narrows the band gap to 2.52 eV (vs. 3.18 eV for ZnO) and extends the photoresponse to ∼550 nm. XPS binding energy shifts confirm interfacial charge redistribution and a built-in electric field that drives directional carrier separation, overcoming the recombination limitation inherent to the quasi-Type-I alignment. Under visible-light irradiation, the optimal 35% ZnO/ZCS achieves 94.66% CIP removal within 120 min (k = 1.85 × 10 –2  min –1 ), markedly outperforming pristine ZnO and ZCS (both <60%). It retains >80% efficiency after five consecutive cycles and >60% removal in tap/surface water across a wide pH range (2.323–9.653). Radical trapping and EPR experiments verify the generation of 1 O 2 , •OH, h + , and •O 2 – , with 1 O 2 identified as the dominant reactive species. LC-MS analysis reveals piperazine ring oxidation and methylation as the initial degradation steps. This work provides a robust MOF-derived heterojunction strategy for efficient photocatalytic antibiotic remediation. Download: Download high-res image (357KB) Download: Download full-size image