Prussian Blue Analogues and Their Derivatives: From Elaborate Microstructure Design to Boosted Fenton-Like Application

Heterogeneous Fenton-like reaction is a promising process for refractory wastewater treatment. Among the various heterogeneous Fenton-like catalysts, Prussian blue (PB) and Prussian blue analogues (PBAs) show great potential for hydrogen peroxide and persulfate activation owing to their low toxicity, simple preparation, and high activity. To further improve the catalytic activity of PBAs and their derivatives (PBDs), many efforts have been made to overcome the instability of the crystal structure and develop feasible methodologies to prepare PBAs/PBDs with diverse morphologies and compositions. In this Account, our recent achievements on novel synthetic strategies to obtain PBAs/PBDs with controlled morphologies, geometric sites, and electronic structures were systematically summarized. The physicochemical properties of the PBAs/PBDs and their contribution to the catalytic reaction in the advanced oxidation processes (AOPs) were also discussed. First, we focus on developing a novel synthesis technology (such as "copolymer-co-morphology" conception) of PBAs with controllable morphology. By regulating the chelating agents, surfactants, metal ions, and preparation conditions and constructing a heterojunction, the stability of PBAs/PBDs was significantly improved to overcome their instability during redox reaction. Notably, to inherit the characteristics of PBAs, a topological transformation strategy was applied to fabricate metal oxides with morphologies similar to those of PBAs through thermal calcination under an aerobic atmosphere. Subsequently, this strategy has been extensively applied to prepare single-atom catalysts, metal nitrides, and zerovalent metals via thermal treatment under inert/reducing atmospheres. These novel strategies provide guidance for devising controllable PBAs/PBDs materials with superior activity and stability during cycling tests not only in Fenton-like reactions but also in other catalytic systems. In addition to the physicochemical property optimization, the relationship between the deliberately designed electronic structure and the catalytic activity of PBAs/PBDs was first explored in depth using 57Fe Mo''ssbauer spectroscopy. Moreover, benefiting from these efficient techniques and conscientious explorations, our research not only elucidated the important descriptors for the intrinsic oxidation pathways but also revealed the significant effect of external energy (ultraviolet and visible light) on the catalytic pathways in PBAs/PBDs-dominant Fenton-like systems. These findings provide a novel inspiration for further application of additional energy. Finally, the recent challenges and development prospects of PBAs/PBDs in AOPs are comprehensively discussed. Overall, this Account provides comprehensive insights into PBAs/PBDs fabrication strategies, physicochemical properties, local electronic structures, and the intrinsic correlation between these characteristics and catalytic mechanisms using advanced analysis techniques and paves the way for the future development of PBAs/PBDs in various catalysis fields.