Full-spectrum efficient photocatalytic pollutant degradation via Cu-N bridged S-type heterojunctions interface and LME effect by single-Fe-atoms

Abstract

Effective separation and utilization of photogenerated charges are pivotal for enhancing the photocatalytic process. In this study, we designed an atomic-level interface chemical bond (Cu-N bond) and successfully synthesized a novel Cu₂O_(x)/Fe@ZIF-NH₂ S-Scheme heterojunction. The Fe@ZIF-NH₂ component was constructed by embedding abundant isolated Fe sites and amine groups within a Zn-MOF (ZIF-8) matrix. Under full solar-spectrum illumination, the Cu-N interface bridge, the local microenvironment (LME) engineered by isolated Fe atoms, and the modulation of the internal electric field synergistically promote directional charge migration. The optimized Cu₂O₍₄₎/Fe@ZIF-NH₂ achieves a superior tetracycline (TC) degradation rate constant of 0.0042 min⁻¹, representing 7-fold and 10.5-fold improvements over pristine Cu₂O and ZIF-8, respectively. Notably, photo-thermal conversion is observed, with the synergistic action of photocatalysis and thermal activation enabling the removal of 98% of TC and over 85% of other pollutants, including ciprofloxacin, coumarin, gentian violet, and methylene blue. Comprehensive characterization confirms the photo-thermal contribution, revealing that Cu₂O acts as a “nano-heater,” while the LME surrounding single Fe atoms accelerates surface reaction kinetics. Mechanistic insights derived from radical trapping experiments, photoelectrochemical tests, and in situ XPS analysis elucidate cooperative charge transfer pathways. This study presents a promising strategy for designing high-performance photocatalysts through interfacial engineering and single-atom modulation for advanced water purification applications.