Advanced oxidation processes (AOPs) have a broad range of potential applications in the treatment of emerging refractory emerging pollutants. However, due to the presence of highly reactive substances such as free radicals that are difficult to capture, it is challenging to investigate the mechanism of AOPs at the elementary reaction level. The conventional methods, such as electron spin resonance (ESR), free radical quantification, and free radical quenching, are plagued by systematic issues that have led to bottlenecks in the field of AOP studies. The development of computational chemistry theory and computer performance provides a new method to study the mechanism of AOPs through density functional theory (DFT) calculation. Due to its excellent cost–performance benefit, DFT calculations for aperiodic small molecules have become popular in the field of AOPs. In this paper, a comprehensive review is presented on the applications of DFT calculations for predicting active sites and exploring reaction selectivity and oxidant activation mechanisms. A systematic classification of methods related to molecular descriptors and transition states is provided. Furthermore, some current research issues are identified, and future development prospects and challenges are discussed.

The pre-designable structure and unique architectures of covalent organic frameworks (COFs) render them attractive as active and porous medium for water crisis. However, the effect of functional basis with different metrics on the regulation of interfacial behavior in advanced oxidation decontamination remains a significant challenge. In this study, we pre-design and fabricate different molecular interfaces by creating ordered pi skeletons, incorporating different pore sizes, and engineering hydrophilic or hydrophobic channels. These synergically break through the adsorption energy barrier and promote inner-surface renewal, achieving a high removal rate for typical antibiotic contaminants (like levofloxacin) by BTT-DATP-COF, compared with BTT-DADP-COF and BTT-DAB-COF. The experimental and theoretical calculations reveal that such functional basis engineering enable the hole-driven levofloxacin oxidation at the interface of BTT fragments to occur, accompanying with electron-mediated oxygen reduction on terphenyl motif to active radicals, endowing it facilitate the balanced extraction of holes and electrons. The synergetic regulation of the electronic structure and interfacial reaction of covalent organic frameworks (COF) for water purification remains a challenge. Here the authors propose that COFs materials possessing molecular interfaces with ordered pi skeletons, suitable pore size, and hydrophilic/hydrophobic channels synergically break through the adsorption energy barrier achieving high removal rates for micropollutants.

Environmental theoretical calculation aims to use computer simulation to assist in solving environmental problems. Herein, we present the guiding principles of environmental theoretical calculation for non-periodic systems. A summary is given of recent progress towards the use of environmental theoretical calculation to reveal the degradation/transformation mechanisms of contaminants in reactions.

Accurately controlling catalytic activity and mechanism as well as identifying structure–activity–selectivity correlations in Fenton-like chemistry is essential for designing high-performance catalysts for sustainable water decontamination. Herein, active center size-dependent catalysts with single cobalt atoms (CoSA), atomic clusters (CoAC), and nanoparticles (CoNP) were fabricated to realize the changeover of catalytic activity and mechanism in peroxymonosulfate (PMS)-based Fenton-like chemistry. Catalytic activity and durability vary with the change in metal active center sizes. Besides, reducing the metal size from nanoparticles to single atoms significantly modulates contributions of radical and nonradical mechanisms, thus achieving selective/nonselective degradation. Density functional theory calculations reveal evolutions in catalytic mechanisms of size-dependent catalytic systems over different Gibbs free energies for reactive oxygen species generation. Single-atom site contact with PMS is preferred to induce nonradical mechanisms, while PMS dissociates and generates radicals on clusters and nanoparticles. Differences originating from reaction mechanisms endow developed systems with size-dependent selectivity and mineralization for treating actual hospital wastewater in column reactors. This work brings an in-depth understanding of metal size effects in Fenton-like chemistry and guides the design of intelligent catalysts to fulfill the demand of specific scenes for water purification.

Singlet oxygen (1O2) plays a crucial role in Fenton-like reactions due to its high efficiency and selectivity in removing trace organic pollutants from complex water matrices. Defect engineering, which allows the efficient exposure of active sites and optimization of electronic structures, has rapidly emerged as a fundamental strategy for enhancing 1O2 yield. Herein, we introduce tunable sulfur vacancy (VS) density into Co9S8 catalysts for peroxymonosulfate (PMS) activation. The modulation of the octahedral Co (CoS6) and tetrahedral Co (CoS4) electronic structures by VS triggers the unexpected selective generation of 1O2. The VS/PMS system exhibits excellent resistance to interference and highly selective degradation of electron-donating organic pollutants. Experimental and theoretical calculations revealed a new evolutionary route for 1O2 involving two phases (Phase I: HSO5− → *O, Phase II: *O + HSO5− →*OO → 1O2). This study provides a molecular-level understanding of VS-mediated catalytic selectivity for high-efficient decontamination applications.

Organophosphorus pesticides are extensively utilized worldwide, but their incomplete dephosphorization poses significant environmental risks. This study investigates the dephosphorization of dimethoate (DMT), a representative organophosphorus pesticide, using a vacuum ultraviolet system. Surprisingly, in addition to hydroxyl radicals (•OH), non-radical processes such as photoexcitation and singlet oxygen atoms (O(1D)) exert more significant effects on DMT dephosphorization. The degradation kinetics of DMT demonstrate a perfect linear correlation with the radical yield in both UV-based and VUV-based advanced oxidation processes (AOPs), with greater efficacy of radical attack observed in the VUV system. This heightened efficiency is attributed to the excitation of DMT to a high-energy excited state induced by UV185 radiation. Additionally, •OH alone is inadequate for achieving complete dephosphorization of DMT. The Fukui index and singly occupied orbital (SOMO) analysis reveal that the O(1D) generated by UV185-induced photolysis of O2 exhibits exceptional selectivity towards P=S bonds, thereby playing an indispensable role in the dephosphorization process of DMT. This study highlights the significant contribution of non-radical pathways in DMT dephosphorization by VUV, which holds great implications for the advancement of photochemical-based AOPs.

Antibiotics have been widely used to treat bacterial diseases. Their wide spread in ecological environment will induce generation of antibiotic-resistant bacteria Therefore, it is critical to create an eco-friendly and effective approach for their removal. Herein, a bimetallic sulfide FeS2@MoS2 with rich sulfur vacancies (SVs) and high percentage of metallic 1T phase MoS2 was prepared by one-step solvothermal method to degrade ofloxacin (OFX) by activated peroxymonosulfate (PMS). FeS2@MoS2-1 (the mass ratio of Fe/Mo is 1) exhibited excellent performance for PMS activation, with 99.26% OFX removed in 20 min (0.2 g/L FeS2@MoS2-1, 0.2 mM PMS, initial pH). The degradation rate constant of kobs was 0.21 min−1 with FeS2@MoS2-1 system, which was about 4.88 and 22.91 times of FeS2/PMS and MoS2/PMS systems under the same experimental conditions respectively. In FeS2@MoS2-1, besides S2−, SVs would also accelerate Fe(III)/Fe(II) circulation through increasing the exposure of Mo(IV) active sites. Additionally, MoS2 transferred from the semi-conductive 2H phase to the metallic 1T phase, which could speed up electron transfer rate significantly. Quenching experiment and EPR test showed that SO4− and O2− were the main active oxygen species. Degradation pathway was proposed through the active sites identification by DFT calculations and intermediates detection by HPLC-MS analyzation. The results showed that OFX were vulnerable to be attacked and broke to form small molecular compounds through hydrogen loss, oxidative cracking, decarboxylation and demethylation four ways. In addition, their bio-toxicity was investigated and results showed that the toxic was diminished. This work indicated that the satisfactory universality, recyclability and stability enabled FeS2@MoS2-1 could be used as an efficient catalyst to activate PMS to degrade refractory organic pollutants in water.

The nanoconfinement effect in Fenton-like reactions shows great potential in environmental remediation, but the construction of confinement structure and the corresponding mechanism are rarely elucidated systematically. Herein, we proposed a novel peroxymonosulfate (PMS) activation system employing the single Fe atom supported on mesoporous N-doped carbon (FeSA-MNC, specific surface area = 1520.9 m2/g), which could accelerate the catalytic oxidation process via the surface-confinement effect. The degradation activity of the confined system was remarkably increased by 34.6 times compared to its analogue unconfined system. The generation of almost 100% high-valent iron-oxo species was identified via 18O isotope-labeled experiments, quenching tests, and probe methods. The density functional theory illustrated that the surface-confinement effect narrows the gap between the d-band center and Fermi level of the single Fe atom, which strengthens the charge transfer rate at the reaction interface and reduces the free energy barrier for PMS activation. The surface-confinement system exhibited excellent pollutant degradation efficiency, robust resistance to coexisting matter, and adaptation of a wide pH range (3.0–11.0) and various temperature environments (5–40 °C). Finally, the FeSA-MNC/PMS system could achieve 100% sulfamethoxazole removal without significant performance decline after 10,000-bed volumes. This work provides novel and significant insights into the surface-confinement effect in Fenton-like chemistry and guides the design of superior oxidation systems for environmental remediation.

Precisely identifying the atomic structures in single-atom sites and establishing authentic structure–activity relationships for single-atom catalyst (SAC) coordination are significant challenges. Here, theoretical calculations first predicted the underlying catalytic activity of Fe–NxC4–x sites with diverse first-shell coordination environments. Substituting N with C to coordinate with the central Fe atom induces an inferior Fenton-like catalytic efficiency. Then, Fe-SACs carrying three configurations (Fe–N2C2, Fe–N3C1, and Fe–N4) fabricate facilely and demonstrate that optimized coordination environments of Fe–NxC4–x significantly promote the Fenton-like catalytic activity. Specifically, the reaction rate constant increases from 0.064 to 0.318 min–1 as the coordination number of Fe–N increases from 2 to 4, slightly influencing the nonradical reaction mechanism dominated by 1O2. In-depth theoretical calculations unveil that the modulated coordination environments of Fe-SACs from Fe–N2C2 to Fe–N4 optimize the d-band electronic structures and regulate the binding strength of peroxymonosulfate on Fe–NxC4–x sites, resulting in a reduced energy barrier and enhanced Fenton-like catalytic activity. The catalytic stability and the actual hospital sewage treatment capacity also showed strong coordination dependency. This strategy of local coordination engineering offers a vivid example of modulating SACs with well-regulated coordination environments, ultimately maximizing their catalytic efficiency.

Vacuum ultraviolet (VUV) based advanced oxidation processes (AOPs) recently attracted widespread interests. However, the role of UV185 in VUV is only considered to be generating a series of active species, while the effect of photoexcitation has long been overlooked. In this work, the role of UV185 induced high-energy excited state for the dephosphorization of organophosphorus pesticides was studied using malathion as a model. Results showed malathion degradation was highly related to radical yield, while its dephosphorization was not. It was UV185 rather than UV254 or radical yield that was responsible for malathion dephosphorization by VUV/persulfate. DFT calculation results demonstrated that the polarity of P-S bond was further increased during UV185 excitation, favoring dephosphorization while UV254 did not. The conclusion was further supported by degradation path identification. Moreover, despite the fact that anions (Cl-, SO42- and NO3-) considerably affected radical yield, only Cl- and NO3- with high molar extinction coefficient at 185 nm significantly affected dephosphorization. This study shed light on the crucial role of excited states in VUV based AOPs and provided a new idea for the development of mineralization technology of organophosphorus pesticides.

Carbon nanotubes (CNTs) and their derivatives have been widely exploited to activate various oxidants for environmental remediation. However, the intrinsic mechanism of CNTs-driven periodate (PI) activation remains ambiguous, which significantly impedes their scientific progress toward practical application. Here, we found that CNTs can strongly boost PI activation for the oxidation of various phenols. Reactive oxygen species analysis, in situ Raman characterization, galvanic oxidation process experiments, and electrochemical tests revealed that CNTs could activate PI to form high-potential metastable intermediates (CNTs–PI*) rather than produce free radicals and 1O2, thereby facilitating direct electron transfer from the pollutants to PI. Additionally, we analyzed quantitative structure–activity relationships between rate constants of phenols oxidation and double descriptors (e.g., Hammett constants and logarithm of the octanol–water partition coefficient). The adsorption of phenols on CNT surfaces and their electronic properties are critical factors affecting the oxidation process. Besides, in the CNTs/PI system, phenol adsorbed the CNT surfaces was oxidized by the CNTs–PI* complexes, and products were mainly generated via the coupling reaction of phenoxyl radical. Most of the products adsorbed and accumulated on the CNT surfaces realized phenol removal from the bulk solution. Such a unique non-mineralization removal process achieved an extremely high apparent electron utilization efficiency of 378%. The activity evaluation and theoretical calculations of CNT derivatives confirmed that the carbonyl/ketonic functional groups and double-vacancy defects of the CNTs were the primary active sites, where high-oxidation-potential CNTs–PI* were formed. Further, the PI species could achieve a stoichiometric decomposition into iodate, a safe sink of iodine species, without the generation of typical iodinated byproducts. Our discovery provides new mechanistic insight into CNTs-driven PI activation for the green future of environmental remediation.

A series of C-doped Bi3O4X (X = Cl, Br, I) photocatalysts with layer-stacked structure was synthesized using glucose as carbon source, and the carbon doping and halogen species on harvesting broader solar spectrum and promoting charge carrier separation were systematically investigated. For pyrene photolysis, the photodegradation rate of pristine materials followed the order of Bi3O4I > Bi3O4Br > Bi3O4Cl, which was attributed to the difference in electronegativity of the halogen elements. The doped carbon boosted photocatalytic performance and the optimal C/Bi3O4I achieved 100% pyrene removal within 20 min, which primarily benefited from the dramatic improvement of the internal electric field (IEF). The improved IEF further increased the separation and transfer efficiency of photogenerated charge carriers. XRD and XPS characterizations confirmed that the doped carbon implanted into the lattice of [X] layers, and mainly affected the X np states. The X np orbitals contributed to the valence band (VB) of Bi3O4X, thus the local occupied states induced by doped carbon formed above VB and significantly decreased the VB potential. Meanwhile, the doped carbon narrowed the band gap and greatly improved visible light utilization. The O2−, h+ and OH were identified as dominant active species for pyrene degradation, and the generation rate of O2− and OH was further measured by the probe technique. Moreover, the photodegradation pathways of pyrene were proposed and the ecotoxicity of intermediates was assessed. This study reveals the effect of halogen species on photocatalytic activity and provides guidance for enhancing IEF by doping inorganic element.

Persulfate-based advanced oxidation processes (AOPs) have obtained increasing attention due to the generation of sulfate radical (SO4•‒) with high reactivity for organic contaminants degradation. Numerous activation methods have been used to activate two common persulfates: peroxymonosulfate (PMS) and peroxydisulfate (PDS). However, the comparisons of activation methods and two oxidants in the comprehensive degradation performance of the target contaminant are still limited. Thus, taking norfloxacin (NOR) as the target contaminant, we proposed five key parameters (the observed pseudo-first-order rate constant, kobs; average mineralization rate, rm; utilization efficiency of catalyst, Ucat; utilization efficiency of oxidant, Uox; and net utilization efficiency of oxidant, Uox’) to quantify the comprehensive degradation performance of NOR. The irradiation affected target pollutants, catalysts, and oxidants, leading to an improved degradation performance of NOR. Various heterogeneous catalysts were compared in terms of the key elements contained. Fe, Co, and Mn-based materials performed better, while carbon-based catalysts performed poorly on NOR degradation. The overall degradation performance of NOR was different for PMS and PDS, which can be ascribed to their varied reaction pathways towards NOR, but stemmed from different properties of PMS and PDS. Besides, the effect of pH on the degradation efficiency of NOR was investigated. A neutral solution was optimal for PMS system, while an acidic solution worked better for PDS system. Finally, we analyzed the molecule structure of NOR by density functional theory (DFT) calculation to study the sites easy to attack. Then, we summarized four typical degradation pathways of NOR in SO4•‒-based AOP systems, including defluorination, piperazine ring cleavage, piperazine ring oxidation, and quinoline group transformation.

Electron paramagnetic resonance (EPR) spectroscopy using sterically hindered amine is extensively applied to detect singlet oxygen (1O2) possibly generated in advanced oxidation processes. However, EPR-detectable 1O2 signals were observed in not only the 1O2-dominated hydrogen peroxide (H2O2)/hypochlorite (NaClO) reaction but surprisingly also the 1O2-absent Fe(II)/H2O2, UV/H2O2, and ferrate [Fe(VI)] process with even stronger intensities. By taking advantage of the characteristic reaction between 1O2 and 9,10-diphenyl-anthracene and near-infrared phosphorescent emission of 1O2, 1O2 was excluded in the Fe(II)/H2O2, UV/H2O2, and Fe(VI) process. The false detection of 1O2 was ascribed to the direct oxidation of hindered amine to piperidyl radical by reactive species [e.g., •OH and Fe(VI)/Fe(V)/Fe(IV)] via hydrogen transfer, followed by molecular oxygen addition (forming a piperidylperoxyl radical) and back reaction with piperidyl radical to generate a nitroxide radical, as evidenced by the successful identification of a piperidyl radical intermediate at 100 K and theoretical calculations. Moreover, compared to the highly oxidative species (e.g., •OH and high-valence Fe), the much lower reactivity of 1O2 and the profound nonradiative relaxation of 1O2 in H2O resulted it too selective and inefficient in organic contaminant destruction. This study demonstrated that EPR-based 1O2 detection could be remarkably misled by common oxidative species and thereby jeopardize the understandings on 1O2.

Peracetic acid (CH3C(O)OOH, PAA)-based heterogeneous advanced oxidation process (AOP) has attacked intensive interests due to production of various reactive species. Herein, Co(OH)2 nanoparticles decorated biochar (Co(OH)2/BC) was fabricated by a simple and controllable method, which was used to degrade tetracycline hydrochloride (TTCH) in water through PAA activation. The results indicated that 100% TTCH (C0 = 10 µmol/L) degradation efficiency was realized within 7 min at pH 7, with a high kinetic rate constant (k1) of 0.64 min−1 by the optimized Co(OH)2/BC. Material characterizations suggested that Co(OH)2 nanoparticle was successfully decorated on biochar, leading to more active sites and electronic structure alteration of biochar, thus greatly promoting the catalytic cleavage of PAA for radicals production. Then, the reactive oxygen species (ROS) quenching experiments and electron paramagnetic resonance (EPR) analysis demonstrated the key species were alkoxyl radicals (R–O•, mainly CH3CO2• and CH3CO3•), HO• and 1O2 in this system. Besides, density functional theory (DFT) calculation on Fukui index further revealed that the vulnerable sites of TTCH and three possible degradation pathways were proposed. This study can provide a new strategy for synthesis functional materials in PAA activation AOPs for removal of antibiotics in water.

Electrochemical disinfection (ED) is effective in removal of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) during wastewater treatment. However, the inner relationship of antibiotic-resistant phenotypes with their genotypes of ARB is still unclear in the ED process. This study explored the disinfection mechanism at the microcosmic level using four Escherichia coli (E. coli) strains with different antibiotic-resistant phenotypes. Results showed that bacteria with multiple antibiotic resistance tended to have stronger viability in disinfection compared with those resistant to fewer antibiotics. Interestingly, antibiotic-resistant phenotypes changed little in the disinfection process, while genotypes closely responded to bacterial resistance of different E. coli. In detail, beta-lactamase resistance genes played a leading role in the cross-resistance between antibiotics and electrochemical oxidation. They were proved to reduce oxidative destruction by increasing the strength of the cell wall and membrane. In addition, diaminopyrimidine and macrolide-lincosamide-streptogramin B resistance genes are also closely related to the bacterial resistance to ED. Combined with the quantitative determination of ARGs, the abundance of IntI1 and aminoglycoside resistance genes can be regarded as indicators for the risk of cross-resistance to antibiotics and electrochemical oxidation. This study provided important references for in depth understanding and accurate control of antibiotic resistance with advanced oxidation processes.

Emerging organic pollutants (EOPs) in water are of great concern due to their high environmental risk, so urgent technologies are needed for effective removal of those pollutants. Herein, a heterogeneous advanced oxidation process (AOP) of peroxymonosulfate (PMS) activation by functional material was developed for degradation of a typical antibiotic, gatifloxacin (GAT). The reactive species including sulfate radical (SO4•−) and singlet oxygen (1O2) in this AOP were regulated by interlayered ions (Na+/H+) of titanate nanotubes that supported on Co(OH)2 hollow microsphere. Both the Na-type (NaTi-CoHS) and H-type (HTi-CoHS) materials achieved efficient PMS activation for GAT degradation, and HTi-CoHS even exhibited a relatively high degradation efficiency of 96.6% within 5 min. Co(OH)2 was considered the key component for generation of SO4•− after PMS activation, while hydrogen titanate nanotubes (H-TNTs) promoted the transformation of peroxysulfate radical (SO5•−) to 1O2 by hydrogen bond interaction. Therefore, when the interlayer ion of TNTs transformed from Na+ to H+, more 1O2 was produced for organic pollutant degradation. H-TNTs with lower symmetry preferred to adsorb PMS molecules to achieve interlayer electron transport through hydrogen bonding, rather than electrostatic interaction of Na+ for Na-TNTs. In addition, the degradation pathway of GAT mainly proceeded by the cleavage of C–N bond at the 8 N site of the piperazine ring, which was confirmed by condensed Fukui index and mass spectrographic analysis. This work gives new sights into the regulation of reactive species in AOPs by the composition of material and promotes the understanding of pollutant degradation mechanisms in water treatment process.

Realizing efficient hydrogenation of N2 molecules in the electrocatalytic nitrogen reduction reaction (NRR) is crucial in achieving high activity at a low potential because it theoretically requires a higher equilibrium potential than other steps. Analogous to metal hydride complexes for N2 reduction, achieving this step by chemical hydrogenation can weaken the potential dependence of the initial hydrogenation process. However, this strategy is rarely reported in the electrocatalytic NRR, and the catalytic mechanism remains ambiguous and lacks experimental evidence. Here, we show a highly efficient electrocatalyst (ruthenium single atoms anchored on graphdiyne/graphene sandwich structures) with a hydrogen radical-transferring mechanism, in which graphdiyne (GDY) generates hydrogen radicals (H•), which can effectively activate N2 to generate NNH radicals (•NNH). A dual-active site is constructed to suppress competing hydrogen evolution, where hydrogen preferentially adsorbs on GDY and Ru single atoms serve as the adsorption site of •NNH to promote further hydrogenation of NH3 synthesis. As a result, high activity and selectivity are obtained simultaneously at −0.1 V versus a reversible hydrogen electrode. Our findings illustrate a novel hydrogen transfer mechanism that can greatly reduce the potential and maintain the high activity and selectivity in NRR and provide powerful guidelines for the design concept of electrocatalysts.

Traditional methods cannot efficiently recover Cu from Cu(II)–EDTA wastewater and encounter the formation of secondary contaminants. In this study, an ozone/percarbonate (O3/SPC) process was proposed to efficiently decomplex Cu(II)–EDTA and simultaneously recover Cu. The results demonstrate that the O3/SPC process achieves 100% recovery of Cu with the corresponding kobs value of 0.103 min–1 compared with the typical •OH-based O3/H2O2 process (81.2%, 0.042 min–1). The carbonate radical anion (CO3•–) is generated from the O3/SPC process and carries out the targeted attack of amino groups of Cu(II)–EDTA for decarboxylation and deamination processes, resulting in successive cleavage of Cu–O and Cu–N bonds. In comparison, the •OH-based O3/H2O2 process is predominantly responsible for the breakage of Cu–O bonds via decarboxylation and formic acid removal. Moreover, the released Cu(II) can be transformed into stable copper precipitates by employing an endogenous precipitant (CO32–), accompanied by toxic-free byproducts in the O3/SPC process. More importantly, the O3/SPC process exhibits excellent metal recovery in the treatment of real copper electroplating wastewater and other metal–EDTA complexes. This study provides a promising technology and opens a new avenue for the efficient decomplexation of metal–organic complexes with simultaneous recovery of valuable metal resources.

Earth abundant transition metal-based materials are widely served as peroxymonosulfate (PMS) activators for degradation of emerging contaminants. However, the agglomeration of catalyst particles and metal ion leaching hinder their practical applications for pollutant decomposition. In this study, a Co3O4-carbonized polyaniline composite (Co3O4/CPANI) was implemented for PMS activation. The Co3O4/CPANI + PMS system exhibited high catalytic performance toward tetracycline (TC) degradation (degradation efficiency of 92.11%, initial TC level of 20 mg/L). Moreover, the practical application potential of Co3O4/CPANI + PMS system was well verified with three antibiotics (i.e., TC, doxycycline (DOX), and ciprofloxacin (CIP)) at highest actual aquatic environmental levels (1.0 and 0.5 mg/L). In the established Co3O4/CPANI + PMS system, both radicals (•O2−, •OH and SO4•-) and non-radical (1O2) contributed to TC degradation, and 1O2 was the dominant reactive oxygen species (ROS). CO groups, oxygen vacancies (OVS), redox pairs of Co2+/Co3+ species, and graphitic N all served as active sites in the PMS activation process, especially, OVS were crucial for the generation of 1O2. This study provides an efficient method for the synthesis of metal-based nanocatalysts with low nanoparticle aggregation and metal leaching which could act as a sustainable PMS activator for the remediation of TC-polluted water environment.