Enhanced organic pollutant degradation in a two-dimensional Fe-doped crystalline carbon nitride membrane with near 100 % singlet oxygen generation through the Fe–O–N configuration

The singlet oxygen ( 1 O 2 )-based nonradical AOP process, realized in carbon materials after nitrogen and metal doping, has drawn much attention in recent years. However, the exclusive generation of 1 O 2 in the specialized two-dimensional (2D) catalytic membranes and the associated contaminant degradation mechanisms remain unclear. Herein, a Fe-doped crystalline carbon nitride (Fe-CCN) material without additional nitrogen doping was developed to preferentially initiate 1 O 2 -based nanoconfined oxidation of organic pollutants in the 2D Fe-CCN membrane/PMS system. Density functional theory calculation revealed that the Fe-O-N configuration formed after Fe doping altered the electronic structure of Fe centers, enhancing PMS adsorption and promoting the thermodynamically favorable generation of the –O* intermediate, leading to fast and highly selective 1 O 2 generation. EPR characterization and ROS quenching experiment also confirmed that the Fe-CCN activated PMS, generating nearly 100 % 1 O 2 . The Fe-CCN membrane/PMS system exhibited excellent resistance to natural organic matter (NOM) interference and dramatically increased Bisphenol A (BPA) degradation kinetics, approximately 590 times faster than in conventional batch systems. Enhanced 1 O 2 exposure concentration within the Fe-CCN membrane nanochannels was supported by EPR data and 1 O 2 exposure simulations. Furthermore, The Fe-CCN membrane/PMS system showed wide pH tolerance, excellent pollutant degradation performance, and high stability. This work underscores the practical significance of 1 O 2 -based oxidation reactions in membrane-confined AOPs for the rapid and efficient removal of organic contaminants from water.