Sulfur vacancy-defective porphyrin-based COF/CdS heterojunction effectively enhanced charge separation for photocatalytic uranium extraction from wastewater under air without hole scavengers

A novel direct Z -scheme heterojunction of 0.25-pCOF/CdS with rich S-vacancy defects was successfully fabricated. • 0.25-pCOF/CdS enabled efficient photocatalytic extraction of U(VI) under air without sacrificial agents. • 0.25-pCOF/CdS showed a consistent photocatalytic extraction ratio of over 98% for U(VI) in a range of 5–100 mg/L. • 0.25-pCOF/CdS achieved an ultrahigh extraction ratio of 99.68% for U(VI) when treating real uranium mine wastewater. • The dual strategy of combining S-vacancy defects and heterojunction engineering effectively enhanced charge separation. Photocatalysis is considered as an attractive approach for treating uranium-containing wastewater. Herein, through in-situ growth of a porphyrin covalent organic framework (pCOF) on CdS nanospheres, a novel direct Z -scheme heterojunction of 0.25-pCOF/CdS with rich S-vacancy defects was successfully prepared for visible-light-driven photocatalytic extraction of U(VI) under an aerobic atmosphere without hole scavengers. The optimized 0.25-pCOF/CdS exhibited a consistent photocatalytic extraction ratio of over 98% for U(VI) in a wide range of 5 to 100 mg/L, with excellent anti-interference ability. Notably, 0.25-pCOF/CdS achieved an ultrahigh extraction ratio of 99.68% for U(VI) when treating real uranium-containing wastewater, accompanied by the substantial removal of Fe 3+ , which contributed to the deep purification of wastewater. The reduced uranium mainly accumulated on the CdS surface as U 3 O 8 , while the ·O 2 − and e − were identified as the dominant active species for U(VI) photocatalytic extraction. The dual strategy reported here combines vacancy defects and heterojunction engineering, effectively enhancing charge separation and accelerating directional charge transfer, thereby improving U(VI) photocatalytic extraction performance, and offers a feasible guideline for designing efficient photocatalysts for uranium extraction from radioactive wastewater. Download: Download high-res image (347KB) Download: Download full-size image