Developing functional carbon nitride materials for efficient peroxymonosulfate activation: From interface catalysis to irradiation synergy

Peroxymonosulfate (PMS)-based advanced oxidation technologies are among the most promising strategies for degrading refractory organic pollutants in water. Recently, carbon nitride (CN) materials have been widely reported for the preparation of PMS activators owing to their unique molecular structures. With the advancement of this research, it is not only the activation ability of CN materials that is considered, but also their inherent photocatalytic performance in the activation system, which further improves the degradation efficiency of organic pollutants and at the same time makes the whole oxidation processes more variable and complex. In this review, we summarize recent work on the activation of PMS with CN. Firstly, in terms of improving the activation performance of PMS at the interface of CN materials, function-imparting strategies and the corresponding catalytic mechanisms of non-metallic and metal-containing CN materials are discussed. Then, the potential photochemical properties of CN materials are highlighted, the synergistic-gain principle for activation reactions at the material interface are discussed, and methods for controlling the optical properties of CN, including regulation of its intrinsic optical properties, the grafting exogenous optical materials, and the construction of heterostructures are reviewed. Finally, the CN-modification strategies and the PMS-activation mechanisms are discussed, and the possible directions and future prospects for this field of research in view of its current uncertainties and bottlenecks are presented.