Dual-field synergy in oxygen-vacancy-rich g-C3N4/BiOCl/PVDF membranes for enhanced piezo-photocatalytic antibiotic degradation

Dual-electric-field coupling of the S-scheme g-C 3 N 4 /BiOCl heterojunction and β-PVDF piezo-polarization modulates oxygen-vacancy energy levels for efficient charge separation. • An oxygen-vacancy-rich g-C 3 N 4 /BiOCl photocatalyst is integrated into a porous PVDF membrane, achieving stable immobilization and rapid mass transport. • The multifunctional membrane delivers a high piezo-photocatalytic rate of 0.04012 min −1 and 98.21 % tetracycline removal under light-mechanical coupling. • The composite membrane exhibits excellent recyclability and enables synergistic piezo-photocatalytic purification for antibiotic-contaminated wastewater. Oxygen vacancies (O Vs ) play an important role in photocatalysis, but exploiting O Vs in heterostructures to achieve efficient electron trapping and directional transport remains challenging. In this study, oxygen-vacancy-rich 2D/2D g-C 3 N 4 /BiOCl nanosheets were prepared via a simple hydrothermal method and immobilized on a porous β-PVDF matrix through a freeze-assisted phase inversion process, forming a flexible piezo-photocatalytic membrane. The results indicate that the built-in electric field of the g-C 3 N 4 /BiOCl heterojunction and the piezoelectric polarization field of PVDF jointly regulate the electronic behavior near O Vs . These two electric fields overlap around the defect sites and favorably modulate the defect energy levels, thereby enhancing the ability of O Vs to capture electrons. This dual-field regulation deepens the defect potential wells, prolongs electron residence time, and suppresses carrier recombination. The piezoelectric field also provides a directional driving force that guides electron transport along the interface and promotes the generation of reactive oxygen species. Using tetracycline as the target pollutant, the g-C 3 N 4 /BiOCl/PVDF-50 % membrane exhibited the highest piezo–photocatalytic activity, with an apparent rate constant of 0.04012 min −1 . Overall, this study elucidates the synergistic mechanism among the piezoelectric field, the heterojunction electric field, and O Vs , and provides an effective strategy for designing high performance flexible piezo-photocatalytic materials. Oxygen‑vacancy‑rich g‑C 3 N 4 /BiOCl nanosheets embedded in a flexible β‑PVDF membrane construct dual electric fields by combining an S‑scheme built‑in field with piezoelectric polarization under mechanical vibration. This dual‑field superposition deepens defect potential wells, facilitates directional charge separation, and enhances defect‑mediated O 2 activation, thereby enabling efficient piezophotocatalytic degradation of tetracycline in aqueous solution. Download: Download high-res image (148KB) Download: Download full-size image