Supramolecular porphyrin/ZnFe layered double hydroxide heterojunction as multifunctional photocatalytic surface for effective sterilization and degradation: Performance and enhanced mechanism insight

Abstract

In this work, supramolecular tetrakis(4-carboxyphenyl)porphyrin/ZnFe layered double hydroxide (S-TCPP/ZnFe-LDH) heterojunction was developed and applied as photocatalytic surface bonding on flexible substrate (cotton fabric, CF) to fabricate an effective photocatalytic platform (S-TCPP/ZnFe-LDH@CF) for antibiotic degradation and bacterial inactivation. In which, S-TCPP/ZnFe-LDH heterojunction was synthesized using an in-situ self-assembly method, and the supramolecular porphyrin nanocrystals can interact with ZnFe-LDH nanosheets via covalently combining. The host catalyst ZnFe-LDH in this photocatalytic platform has limited photocatalytic activity. The introduction of photosensitive S-TCPP can effectively improve the activity of the photocatalytic surface. The photocatalytic degradation rate of antibiotic ciprofloxacin over S-TCPP/ZnFe-LDH@CF was 2.87 times higher than ZnFe-LDH@CF. The easy-recovered S-TCPP/ZnFe-LDH@CF also can completely inactivate typical Gram bacteria (106 CFU/mL) within 60 min of visible light irradiation. Moreover, S-TCPP/ZnFe-LDH@CF retained considerable stability and durability without obvious metal ions leakage after the reaction. The results of free radical quenching experiments, ESR tests, photoelectrochemical studies and band structures analyses indicate that the combination of S-TCPP and ZnFe-LDH was closely related to a type II photocatalysis heterojunction with the matched band positions. And S-TCPP/ZnFe-LDH heterojunction demonstrated the ability to effectively activate molecular oxygen via both electron transfer and energy transfer approaches to produce multiple reactive oxygen species. The grafting of S-TCPP on ZnFe-LDH broadened the light response range and intensity, as well as enhanced electron transfer and charge separation, showing significantly improved water purification and disinfection capabilities. This work provides a new advanced photocatalytic surface based on photoactive LDH combined with photosensitive supramolecular materials for the efficient treatment of wastewater containing organic pollutants and biohazards.