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The freshwater scarcity and inadequate access to clean water globally have rallied tremendous efforts in developing robust technologies for water purification and decontamination, and heterogeneous catalysis is a highly-promising solution. Sub-nanometer-confined reaction is the ultimate frontier of catalytic chemistry, yet it is challenging to form the angstrom channels with distributed atomic catalytic centers within, and to match the internal mass transfer and the reactive species' lifetimes. Here, we resolve these issues by applying the concept of the angstrom-confined catalytic water contaminant degradation to achieve unprecedented reaction rates within 4.6 Å channels of two-dimensional laminate membrane assembled from monolayer cobalt-doped titanium oxide nanosheets. The demonstrated degradation rate constant of the target pollutant ranitidine (1.06 ms−1) is 5–7 orders of magnitude faster compared with the state-of-the-art, achieving the 100% degradation over 100 h continuous operation. This approach is also ~100% effective against diverse water contaminates with a retention time of <30 ms, and the strategy developed can be also extended to other two-dimensional material-assembled membranes. This work paves the way towards the generic angstrom-confined catalysis and unravels the importance of utilizing angstrom-confinement strategy in the design of efficient catalysts for water purification. Subnanometer-confined reaction is the frontier of catalytic chemistry, yet it is challenging to form the angstrom channels with distributed atomic catalytic centers within, and to match the internal mass transfer and the reactive species' lifetimes. Here, the authors resolve these issues by applying the concept of the angstrom-confined catalytic water contaminant degradation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Assembling LMO into a catalytic membrane improved performance. • LMO membrane/PMS system achieved 85–96% degradation of several PPCPs. • The (001) surfaces and (100) edges of LMO membrane could spontaneously activate PMS. • LMO membrane performance was stable for 29 h via radical and nonradical pathways. • DFT calculations showed reaction mechanisms of different LMO active sites. Application of peroxymonosulfate (PMS)-based Fenton-like heterogeneous catalysis in water treatment remains scarce due to mass transfer limitation and poor yield of reactive oxygen species (ROS). Herein, assembling reactive CoAl-layered metal oxide (LMO) into the gravity-driven catalytic membrane was carried out to overcome the inherent limitations. Indeed, compared to the conventional batch reactor (less than 35% removal), the LMO membrane/PMS system achieved effective degradation (94.17%) of the probe chemical ranitidine along with several other selected pharmaceuticals and personal care products (PPCP, >80%). This, as predicted by density functional theory calculations, could be attributed to remarkable activation of PMS by the exposed (001) surfaces and (100) edges of CoAl-LMO, spontaneously generating ROS for PPCP degradation. Electron charge density difference analysis estimated efficient charge accumulation and depletion between PMS and LMO, implying strong interaction and charge transfer in the LMO membrane/PMS system. Notably, ROS quenching experiments and electron paramagnetic resonance spectroscopy confirmed the theoretical findings, which showed that PPCP degradation in the LMO membrane/PMS system is caused by both the radicals (SO 4 •− + •OH = 51.97%) and nonradicals (1O 2 = 20.58%) pathways. The LMO membrane achieved long-term stable performance (>90% removal), and the analysis of the used membrane suggested an increase in the relative distribution of oxygen vacancies or ≡Co–OH species, which is favourable for PMS activation. Overall, this study offers a simple strategy for efficient removal of several PPCPs, which could be applied sustainably in water treatment. [ABSTRACT FROM AUTHOR]

• Mesoporous CuCo 2 O 4 @CNTs (M-CuCo 2 O 4 @CNTs) exhibited a long-lasting catalytic reactivity. • M-CuCo 2 O 4 @CNTs with strong surface adsorption capacity avoid the risk of cobalt-metal leaching. • E H -pH diagram revealed the evolution mechanism of M-CuCo 2 O 4 @CNTs at various pH conditions. • A new perspective for the oxidation behavior and eco-toxicity change of ranitidine (RAN) was proposed. • Theoretical calculations coupled with experiments demonstrated the mechanism of PMS activation. The sluggish redox cycle occurring during the oxidation processes and the biological toxicity caused by the leaching of dissociated cobalt ions dramatically hinder the practical application of cobalt-based catalysts. Herein, we synthesized the hydroxylated multi-walled CNTs coated with mesoporous CuCo 2 O 4 (M-CuCo 2 O 4 @CNTs) to enhance peroxymonosulfate (PMS) activation. The introduction of CNTs enabled M-CuCo 2 O 4 @CNTs with a much better thermal stability. M-CuCo 2 O 4 @CNTs with dual electron-rich active sites (≡Co and ≡Cu) exhibited a long-lasting reactivity for the rapid degradation of micropollutants under mild conditions. In the process of PMS activation, the Cu+/Cu2+ redox couple as an electron donor participated in the conversion of Co3+ to Co2+ through rapid charge transfer. More importantly, this functional material with a highly interconnected conductive network and a strong surface adsorption effect significantly limited the leaching of cobalt ions. Meanwhile, the acute toxicity (LC 50 and EC 50) and the chronic toxicity (ChV) of the intermediates of RAN were significantly reduced compared with RAN after the treatment of the M-CuCo 2 O 4 @CNTs/PMS reaction system. DFT calculations were coupled with experiments to prove that PMS molecules were more favorable to be activated at ≡Co sites compared with ≡Cu sites. Finally, this study offered a new perspective for the activation mechanism of PMS-induced heterogeneous oxidation and an attractive alternative for micropollutants elimination in water treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nanoconfinement catalysis is implemented within Co-Cu ONS membrane nanochannels. • Co-Cu ONS membrane achieves ∼ 100% removal of organic pollutants within 86 ms. • The degradation rate is 103−5 times faster compared with the best state-of-the-art. • Oxygen vacancies facilitate electron transfer between metal cations and PMS. • DFT calculations illustrate the mechanism of nanoconfinement catalysis. Practical applications for the degradation of organic contaminants by conventional batch-mode heterogeneous advanced oxidation processes remain elusive due to mass-transfer limitations of short-lived reactive oxygen species (ROS). Nanoconfinement catalysis has received increasing attention because of enhanced reaction efficiency and mass and electron transfer. Here, we implemented the concept of nanoconfinement catalysis using a two-dimensional membrane. Ultrathin cobalt-copper oxide nanosheets (Co-Cu ONS) rich in active sites and oxygen vacancies were prepared through a facile solution reduction method. The assembled Co-Cu ONS membrane with active sites confined within membrane nanochannels spontaneously activates peroxymonosulfate and facilitates the generation of ROS and the redox cycles of metal cations. Therefore, an ultimate degradation efficiency (∼100%), ultrafast (∼86 ms) decomposition of organic pollutants, and excellent catalytic stability (greater than120 h) were achieved. The degradation rate is 103−5 times faster than the best state-of-the-art. This approach offers an attractive alternative for water purification with membrane-based nanoconfinement catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three-dimensional ordered mesoporous Co 3 O 4 (OM-Co 3 O 4) was synthesized. • OM-Co 3 O 4 exhibited excellent catalytic performance for ranitidine (RAN) removal. • OM-Co 3 O 4 achieved the RAN removal efficiency of 99.2% within 7 min. • PMS activation by OM-Co 3 O 4 involved non-radical and radical pathways. • Oxygen vacancies facilitated the catalytic performance of OM-Co 3 O 4. Peroxymonosulfate (PMS)-induced advanced oxidation processes hold great promise for the in-depth treatment of many challenging pollutants. Herein, three-dimensional ordered mesoporous Co 3 O 4 (3D OM-Co 3 O 4) was synthesized with a KIT-6 template to boost PMS activation for the rapid removal of a target pollutant of ranitidine (RAN). At the optimal conditions, 3D OM-Co 3 O 4 achieved the RAN removal efficiency of 99.2% and the RAN mineralization efficiency of 63.7% within 7 min. PMS activation by 3D OM-Co 3 O 4 involved simultaneous non-radical and radical pathways, with the latter accounting for 73.2% of the total RAN removal efficiency. Density functional theory calculations demonstrated that compared with Co 3 O 4 nanoparticles, the adsorption energy of PMS molecules bonded to 3D OM-Co 3 O 4 was increased from −0.213 eV to −0.297 eV due to its ordered mesoporous structure. The regeneration of 3D OM-Co 3 O 4 by a reduction treatment indicated that its catalytic stability was associated with rapid charge transfer between the Co(III)/Co(II) redox couple. The possible degradation pathways revealed the oxidation behavior of RAN in the 3D OM-Co 3 O 4 /PMS heterogeneous system. This study provides a new perspective for the mechanism of PMS-induced heterogeneous catalytic oxidation and a novel method for enhancing the synergistic effect between Co 3 O 4 nanoparticles. [ABSTRACT FROM AUTHOR]

[Display omitted] • BN-Co 3 O 4 nanosheet cluster (NC) was synthesized by a facile two-step method. • BN-Co 3 O 4 NC/PMS exhibited a remarkably catalytic performance for ranitidine removal. • PMS activation by BN-Co 3 O 4 NC was mainly due to the reduction via radical pathway. • DFT calculations demonstrated the mechanism of PMS activation. • BN-Co 3 O 4 NC offered confined channels to fast the heterogeneous catalysis. Peroxymonosulfate (PMS) induced advanced oxidation processes hold great promise for heterogeneous oxidation reactions. In this study, boron nitride (BN)-Co 3 O 4 nanosheet cluster (NC) was fabricated to facilitate PMS activation with a nanoconfined heterogeneous catalysis effect for the rapid removal of ranitidine (RAN) under mild conditions. The obtained BN-Co 3 O 4 NC cluster exhibited efficient catalysis performance with a 99.5% removal efficiency for ranitidine in 5 min, and meanwhile this novel catalyst could be applied under a wide pH range (pH: 3–9) with still high degradation efficiencies. The porous structure of BN-Co 3 O 4 NC provided a large number of channels for RAN and PMS molecules to enter the catalyst's inner confinement space, resulting in a remarkable enhancement of catalytic performance. The kinetic rate constant for RAN degradation by the BN-Co 3 O 4 NC/PMS system with 3–33 fold less catalyst dosage is much larger (1.58–213 fold) compared with the state-of-the-art. PMS activation by BN-Co 3 O 4 NC was mainly due to the pathway of reduction via active radicals. Density functional theory calculations specified that the concomitant active radicals such as ∙OH and SO 4 ∙− were mainly derived from PMS activation via O-O bond cleavage. This work provides a new perspective for regulating the structure of Co 3 O 4 and elucidating the mechanism of PMS-induced heterogeneous catalytic oxidation. [ABSTRACT FROM AUTHOR]