Facile synthesis of Fe-doped Zn-based coordination polymer composite with enhanced visible-light-driven activity for degradation of multiple antibiotics

We developed the novel Fe-doped Zn-based coordination polymer (CP) composites (Fe@Zn-CP-n, n = 1-3) with superior visible-light-driven photocatalytic activity. Herein, the Fe@Zn-CP composites were prepared using a newly designed Zn-CP {[Zn(3-padpe)(1,3-BDC)]center dot H2O}n using mixed ligands 4,4 '-bis(3-pyridylformamide) diphenylether (3-padpe) and 1,3-benzenedicarboxylic acid (1,3-H2BDC) and FeSO4 by a facile approach at room temperature. The degradation of several tetracyclines (TCs), such as chlortetracycline (CTC), tetracycline hydrochloride (TC), and oxytetracycline (OTC) under visible-light irradiation were used to assess the photocatalytic performance. The generated ideal Fe@Zn-CP-2 composite showed high photocatalytic activity under visible light irradiation, for which the removal rate of antibiotics were 90.60% for CTC in 100 min, 90.00% for TC in 100 min, and 87.70% for OTC in 30 min, respectively. The superior photocatalytic performance was attributed to the Fe-O bond formation which expanded the optical absorption range and significantly increased the separation effectiveness of photogenerated charges. These properties enhanced the photoactivity of Fe@Zn-CP-2 for photocatalytic reaction under visible light irradiation. Additionally, the Fe@Zn-CP-2 showed excellent photostability and recycleability. The detailed intermediates and pathway of CTC degradation were also illustrated. According to the quenching studies and electron spin resonance (ESR) spectra characterization, the main species involved in the photocatalytic reaction were the radicals h(+) and O-center dot(2)-. In addition, the possible photocatalytic reaction mechanisms were deeply discussed. This work offers fresh insight into the design of CP-based photocatalytic materials and demonstrates the broad application potential of Fe@Zn-CP composites in environmental remediation.