Ultrathin porous nitrogen-doped carbon nanosheets with rich defects for efficient Cr(VI) reduction

Herein, the ultrathin porous nitrogen-doped carbon nanosheet (uPNC-NS-800) catalyst was developed for efficient Cr(VI) reduction. Its versatile structures were obtained via thermal exfoliation of metal-organic frameworks with KCl. Impressively, uPNC-NS-800 achieved complete reduction of Cr(VI) to Cr(III) within only 6 min in oxalic acid (OA) aqueous solution, exhibiting significantly higher catalytic efficiency compared to PNC-NS-800, which lacks ultrathin structure. It also retained high catalytic activity after twelve cycles and exhibited excellent applicability, effectively removing Cr(VI) from various water environment within 30 min. Additionally, electron paramagnetic resonance spectroscopy indicated that uPNC-NS-800 promoted the generation of ·CO 2 − and ·OH radicals from OA, accelerating Cr(VI) reduction. Density functional theory calculations suggested that Defect C was the dominated active center and Pyridine N, Pyrrole N, and Graphite N were the synergistic active sites to together facilitate Cr(VI) reduction. This study provides a new insight into designing efficient carbon-based catalysts for real environmental wastewater remediation.