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Heterogeneous Fenton catalysis offers a promising alternative to traditional Fenton oxidation for water treatment as its wider operating pH range and high cyclic performance. However, designing catalysts that can activate H2O2 both actively and selectively to mineralize refractory pollutants remains challenging. Here, a state‐of‐the‐art design principle of constructing spatially separated Fe‐M (M denotes an oxophilic first‐row transition metal) dual single‐atom sites is developed for Fenton‐like catalysis. This strategy enables accelerated redox cycles between the dual metal centers, leading to precise manipulation of Fe···O‐O···M intermediate in H2O2 activation. This, in turn, aids the homolytic decomposition of H2O2 toward selective and efficient •OH generation. Taking Fe‐Cu pairs as an example, the constructed dual sites outperform the individual Fe or Cu sites, demonstrating a higher activation selectivity (94%) for •OH production. Further benefitting from the electronic communications between Fe (electron acceptor) and Cu (electron donor), the SA‐Fe‐Cu‐CN catalyst exhibited an effective H2O2 decomposition with 0.94 mm of •OH yielded within 50 min. Compared to the typical homogeneous system, the SA‐Fe‐Cu‐CN/H2O2 system has higher mineralization capacities toward refractory pollutants and greater pH tolerance. The work provides a new strategy for the design of robust catalysts by creating spatially separated dual single‐atom sites toward multi‐reactant systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • SA-Co-NBC-0.2/PMS system shown excellent performance for abating various OMs. • 1O 2 was the major electrophilic species for OMs removal in SA-Co-NBC-0.2/PMS system. • The transformation products evolution and degradation pathways were proposed. • The toxicity of degradation intermediates was analyzed by QSAR prediction. • The ability of SA-Co-NBC-0.2/PMS system to treat wastewater was comprehensively checked. The global shortage of freshwater and inadequate supply of clean water have necessitated the implementation of robust technologies for wastewater purification, and Fenton-like chemistry is a highly-promising approach. However, realizing the rapid Fenton-like chemistry for high-efficiency degradation of organic micropollutants (OMs) remains challenging. Herein, one novel system was constructed by a Co single-atom catalyst activating peroxymonosulfate (PMS), and the optimal system (SA-Co-NBC-0.2/PMS) achieved unprecedented catalytic performance towards a model OM [Iohexol (IOH)], i.e. , almost 100% decay ratio in only 10 min (the observed rate constant: 0.444 min−1) with high electrophilic species 1O 2 (singlet oxygen) generation. Theoretical calculations unveiled that Co-N 4 sites preferred to adsorb the terminal-O of PMS (more negative adsorption energy than other O sites: –32.67 kcal/mol), promoting the oxidation of PMS to generate 1O 2. Iodine (I)23 (0.1097), I24 (0.1154) and I25 (0.0898) on IOH with higher f – electrophilic values were thus identified as the main attack sites. Furthermore, 16S ribosomal RNA high-throughput sequencing and quantitative structure–activity relationship analysis illustrated the environmentally-benign property of the SA-Co-NBC-0.2 and the tapering ecological risk during IOH degradation process. Significantly, this work comprehensively checked the competence of the SA-Co-NBC-0.2/PMS system for organics abatement in practical wastewater. [ABSTRACT FROM AUTHOR]

Amongst various Fenton‐like single‐atom catalysts (SACs), the zinc (Zn)‐related SACs have been barely reported due to the fully occupied 3d10 configuration of Zn2+ being inactive for the Fenton‐like reaction. Herein, the inert element Zn is turned into an active single‐atom catalyst (SA−Zn−NC) for Fenton‐like chemistry by forming an atomic Zn−N4 coordination structure. The SA−Zn−NC shows admirable Fenton‐like activity in organic pollutant remediation, including self‐oxidation and catalytic degradation by superoxide radical (O2⋅−) and singlet oxygen (1O2). Experimental and theoretical results unveiled that the single‐atomic Zn−N4 site with electron acquisition can transfer electrons donated by electron‐rich pollutants and low‐concentration PMS toward dissolved oxygen (DO) to actuate DO reduction into O2⋅− and successive conversion into 1O2. This work inspires an exploration of efficient and stable Fenton‐like SACs for sustainable and resource‐saving environmental applications. [ABSTRACT FROM AUTHOR]

The spread of sustainable lignin-first biomass valorization has widely emphasized to bridge structure-activity relationships of highly-dispersed metallic-nitrogen-carbons in heterogeneous catalytic reaction, yet still challenging due to poor control of the local coordination environment. In the present work, we prepared the mass production of reactive M-N-C catalysts (M=Co, Fe, Mo, Ni and Mn) from well-defined lignin as a renewable bio-ligand via strong metal-coordination sites. A systematic investigation of decomposing tetracycline (TC) was carried out to evaluate the versatile paths of peroxymonosulfate (PMS) activation by mediating metallic redox sites, working pH adaptability, and cycling lifespan. The Co-N-C activated PMS system delivers an ultrahigh catalytic TC oxidation (98.82 %), followed by the Fe-N-C (96.79 %), Mn-N-C (94.8 %), Ni-N-C (90.17 %) and Mo-N-C (66.12 %). Benefitting from the unique electronic structures, zeta potentials, and multi-valent metallic species, the Co-N-C and Mn-N-C enable the efficient TC removal with stable reaction kinetics over the full pH range of 3−11, in which the Co-N-C also delivers a robust retention of ∼92.7 % even after consecutive five cycles. Through the in-situ trapping, the superoxide radicals (O 2 •−) dominate the TC oxidation by the low-valent Co species, whereas the main reactive oxygen species (ROS) of singlet oxygen (1O 2) is triggered by the Fe-N-C-aided PMS system. Accompanied by the theoretical simulation and charge transfer, a coupled behavior from tunable ROS and direct electron shuttling is exerted to adsorbing PMS on specific spin-state of the metallic spots and subsequent cleaving O–O in PMS within the multiple intermediates. We believe that this work not only dedicates to draw a blueprint of customizing lignin-coordinated metallic catalytic activity in the Fenton-like chemistry, but also affords the in-depth potentials of multifunctional water remediation within a waste-treats-pollutant scenario. [Display omitted] • Lignin as a natural bio-ligand to shape M-N-C catalysts by local metal-coordination. • Steering the reactive M-N-C to ignite high-performance Fenton-like chemistry. • Differing the paths and activities of PMS activation by tunable metal-redox sites. • Co-N-C and Mn-N-C remove TC with stable reaction kinetics over the pH range of 3−11. • The catalytic mechanism of TC removal is proposed with the aid of DFT simulation. [ABSTRACT FROM AUTHOR]

• A series of co-catalysis strategies have been assessed by multiple comparison. • Recent development of amplified devices based on co-catalysis systems were discussed. • The scale-up performances of amplified co-catalysis devices have been assessed. • Future guiding strategies for co-catalysis strategy were outlined via TEA, LCA and ML. Recently, great effects have been made for the co-catalysis strategy to solve the bottlenecks of Fenton system. A series of co-catalysis strategies using various inorganic metal co-catalysts and organic co-catalysts have been developed in various oxidant (i.e., hydrogen peroxide (H 2 O 2) and persulfate) systems with significantly promotion of catalytic performances and lower oxidant consumption (only 5–10 % of conventional Fenton/Fenton-like systems). However, the developments of these co-catalysis strategies from theoretical understandings to practical applications and future guiding strategies were overlooked, which was an essential problem that must be considered for the future scale-up applications of co-catalysis systems. In this paper, these co-catalysis strategies with low-oxidant-consumption characteristics have been reviewed by the comparison of their co-catalysis mechanisms, as well as their advantages and disadvantages. We also discussed the recent developments of amplifying devices based on the co-catalysis systems. The scale-up performances of co-catalysis strategies based on these amplifying devices have also been assessed. In addition, future guiding strategies for the development of co-catalysis strategy with low-oxidant-consumption characteristics have also been first time outlined by the combination of the technical-economic analysis (TEA), life cycle assessment (LCA) and machine learning (ML). Finally, the paper systematically discusses the development opportunities, technical bottlenecks and future development directions of co-catalysis strategies with the prospect of large-scale applications. Basically, this work provides a systematic review on co-catalysis strategy with low-oxidant-consumption characteristic from theoretical understandings to practical applications and future guiding strategies. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] An efficient electrophilic thiocyanation of phenols and anilines in the CeBr 3 / H 2 O 2 system has been developed. The system CeBr 3 / H 2 O 2 generates reactive brominating species which would react with NH 4 SCN to deliver the active SCN cations in situ. The Br- anion can be further oxidized to Br+, thereby furnishing the catalytic cycle. [ABSTRACT FROM AUTHOR]

Acidithiobacillus ferrooxidans (At. ferrooxidans) is a bacterium that has the ability to metabolize iron. It converts Fe2+ into Fe3+ during its metabolic cycle. Hence, the At. ferrooxidans spent medium is rich in Fe3+. The presence of Fe3+ contributes to a peroxidase-like activity. Therefore, in this study, an attempt has been made to explore the peroxidase-like activity of the At. ferrooxidans spent medium. It has been observed that the At. ferrooxidans spent medium oxidized 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2). The effect of various process parameters on the peroxidase-like activity has been studied. Optimum peroxidase-like activity is achieved using 5 µl of the spent medium, 0.3 mM TMB concentration, 4 mM H2O2 concentration, 4.2 pH, and 40 °C temperature. The peroxidase-like activity of the At. ferrooxidans spent medium has been used to develop a colorimetric assay for detection of glutathione (GSH). GSH inhibits the peroxidase-like activity of the At. ferrooxidans spent medium in a concentration range of 0–1 mM. The limit of detection (LOD) of GSH, obtained using the calibration plot is 0.69 mM. The developed assay is selective toward GSH, as the presence of amino acids, metals, and sugars have shown a negligible effect on the GSH sensing ability. [ABSTRACT FROM AUTHOR]

Differences in physical structure (e.g. , size, morphology, and exposed facets) will lead to divergence in the understanding of Fenton-like mechanisms. Herein, an iron oxide nanosheet predominated by (3 1 1) facet was prepared by the ultrasonic-assisted method to reveal the single factor of the catalytic descriptors. The adsorption energy of H 2 O 2 on the (3 1 1) facet was only −0.99 eV, which was lower than that on other facets such as (4 0 0) and (2 2 0). Moreover, the energy barriers for the H 2 O 2 activation on (4 0 0), (2 2 0) and (3 1 1) facets were 0.82, 0.64 and 0.30 eV, respectively. This will facilitate the adsorption and activation of H 2 O 2 on the (3 1 1) facet during hydroxyl radicals (HO•) formation. Furthermore, intermediate O 2 •- adsorbed on the (3 1 1) facet will act as a precursor to form the first-excited-state singlet oxygen (1O 2) for advanced oxidation of pollutants. Additionally, the nanosheet structure and good electrochemical properties of the Fe 2 O 3 -sheet will also facilitate electron transfer in Fe 2 O 3 -sheet/H 2 O 2 system. Overall, this study provides a comprehensive view on the relationship between exposed facets and the efficiency of H 2 O 2 activation, and optimizes the design of catalysts with high Fenton-like activity in the deep purification of wastewater. [Display omitted] • Iron oxide nanosheet dominated by (3 1 1) facet was prepared by ultrasonic method. • Relationship between the facets and the efficiency of H 2 O 2 activation was explored. • The energy barrier for the H 2 O 2 activation was the lowest on the (3 1 1) facet. • The first-excited-state singlet oxygen was generated on the (3 1 1) facet. [ABSTRACT FROM AUTHOR]

In this work, crystalline boron is applied as a green co-catalyst to accelerate the redox processes in the Fe(III)/PMS(peroxymonosulfate) system. The semi-metallic B-B bonds in the icosahedra B 12 unit of boron will donate electrons to reduce Fe(III) to initiate Fenton-like PMS activation to generate hydroxyl radical (•OH), sulfate radical (SO 4 •−) and high-valence Fe(IV). Meanwhile, surface boron can directly cleave the peroxide O-O bonds of PMS molecules to produce •OH. The contributions of radical and Fe(IV) can be regulated by Fe(III) dosage, and parallel radical and nonradical oxidation will enable non-selective degradation of diverse organic contaminants with high PMS utilization efficiency. Moreover, Fe(III) accelerates the self-clean of boron surface and secures continuous exposure of active sites. Spontaneously, boron experiences stepwise oxidation and hydrolysis into soluble products without generating toxins. The novel Boron/Fe(III)/PMS system overcomes the rate-limiting step in Fenton chemistry and realizes exceptional efficiency and stability in long-term operations. [Display omitted] • Boron can strongly boost iron/PMS system to non-selectively oxidize diverse organic contaminants. • Reactive radicals and Fe(IV) were produced for the oxidation of organic contaminants. • Boron stepwise donates electrons for direct and indirect Fenton-like activation of PMS. • Boron self-cleaning capability maintains a reactive boron surface for long-term operations. • Boron outperforms all previously reported co-catalysts for boosting the iron/PMS system. [ABSTRACT FROM AUTHOR]

Fluorescent carbon dots (CDs) have aroused great interest in the nanomedicine due to their excellent chemical stability and biological compatibility. However, carbon dots-based nanoplatform integrated with targeted cancer imaging and responsive drug delivery are still challenging. Herein, we synthesized strongly green-fluorescent, cancer-cell-targeted and cationic carbon dots (HP-CDs) via hydrothermal method, by using hyaluronic acid (HA) and polyetherimide together as the starting materials. The nanoprobe could be specifically internalized with cancer cells, due to the recognition of surface HA with highly-expressed CD44 receptor. Ferrocenylseleno-dopamine (FcDA) was particularly designed as new generation drug of Fenton-like reagents, assembled on the surface of HP-CDs to obtain CDs@FcDA nanoprobe. In CDs@FcDA nanoprobe, FcDA significantly quenched CDs fluorescence due to photo-induced electron transfer. Upon the cellular specific uptake, ferrocene moiety of the nanoprobe would be oxidized into ferrocenium cation by intracellular H 2 O 2 in a typical Fenton-like reaction, which resulted in charge reversal and drug release from HP-CDs surface. The quenched nanoprobe fluorescence was thus recovered and achieved the cancer-cell-specific imaging. Meantime, the Fenton chemistry produced toxic •OH, leading to the cancer cell apoptosis. Importantly, the composites of CDs@FcDA exhibited lower IC 50 value than that of free FcDA for HeLa cell lines, indicating greater therapeutic efficiency of the drug nanoplatform. Moreover, oxidized ferrocenium could react with endogenous glutathione (GSH) and be reversibly restored to the reduced ferrocene, which formed a Fenton-chemistry cycle regulated by H 2 O 2 and GSH in cancer microenvironment. Therefore, the HA-functionalized CDs@FcDA nanoprobe proposed in this work represents an attractive tool for redox-gated imaging and cancer-cell-responsive drug delivery. A self-targeted and redox-gated nanoprobe was designed by using ferrocenylseleno-functionalized fluorescent carbon dots to achieve cancer-cell responsive theranostics. [Display omitted] • A self-targeted and FcDA-functionalized fluorescent probe of CDs@FcDA is presented for cancer-cell responsive theranostics. • FcDA-based Fenton-like chemistry facilitates the "turning-on" fluorescence imaging and redox-gated drug delivery. • The composites of CDs@FcDA exhibited lower IC 50 value than that of free FcDA for Fenton therapy of cancer cells. [ABSTRACT FROM AUTHOR]