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In the pursuit of efficient singlet oxygen generation in Fenton-like catalysis, the utilization of single-atom catalysts (SACs) emerges as a highly desired strategy. Here, a discovery is reported that the single-atom Fe coordinated with five N-atoms on N-doped porous carbon, denoted as Fe-N5/NC, outperform its counterparts, those coordinated with four (Fe-N4/NC) or six N-atoms (Fe-N6/NC), as well as state-of-the-art SACs comprising other transition metals. Thus, Fe-N5/NC exhibits exceptional efficacy in activating peroxymonosulfate for the degradation of organic pollutants. The coordination number of N-atoms can be readily adjusted by pyrolysis of pre-assembly structures consisting of Fe3+ and various isomers of phenylenediamine. Fe-N5/NC displayed outstanding tolerance to environmental disturbances and minimal iron leaching when incorporated into a membrane reactor. A mechanistic study reveals that the axial ligand N reduces the contribution of Fe-3d orbitals in LUMO and increases the LUMO energy of Fe-N5/NC. This, in turn, reduces the oxophilicity of the Fe center, promoting the reactivity of *OO intermediate-a pivotal step for yielding singlet oxygen and the rate-determining step. These findings unveil the significance of manipulating the oxophilicity of metal atoms in single-atom catalysis and highlight the potential to augment Fenton-like catalysis performance using Fe-SACs.

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Antimony (Sb) decontamination in water is necessary owing to the worsening pollution which seriously threatens human life safety. Designing bismuth-based photocatalysts with hydroxyls have attracted growing interest because of the broad bandgap and enhanced separation efficiency of photogenerated electron/hole pairs. Until now, the available photocatalysis information regarding bismuth-based photocatalysts with hydroxyls has remained scarce and the contemporary report has been largely limited to Bi3O(OH)(PO4)2 (BOHP). Herein, Bi3O(OH)(AsO4)2 (BOHAs), a novel ultraviolet photocatalyst, was fabricated via the co-precipitation method for the first time, and developed to simultaneous photocatalytic oxidation and adsorption of Sb(III). The rate constant of Sb(III) removal by the BOHAs was 32.4, 3.0, and 4.3 times higher than those of BiAsO4, BOHP, and TiO2, respectively, indicating that the introduction of hydroxyls could increase the removal of Sb(III). Additionally, the crucial operational parameters affecting the adsorption performance (catalyst dosage, concentration, pH, and common anions) were investigated. The BOHAs maintained 85% antimony decontamination of the initial yield after five successive cycles of photocatalysis. The Sb(III) removal involved photocatalytic oxidation of adsorbed Sb(III) and subsequent adsorption of the yielded Sb(V). With the acquired knowledge, we successfully applied the photocatalyst for antimony removal from industrial wastewater. In addition, BOHAs could also be powerful photocatalysts in the photodegradation of organic pollutants studies of which are ongoing. It reveals an effective strategy for synthesizing bismuth-based photocatalysts with hydroxyls and enhancing pollutants' decontamination.

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5-hydroxymethylfurfural (HMF) is a valuable and essential platform chemical for establishing a sustainable, eco-friendly fine-chemical and pharmaceutical industry based on biomass. The cost-effective production of HMF from abundant C6 sugars requires mild reaction temperatures and efficient catalysts from naturally abundant materials. Herein, we report how fulvic acid forms complexes with Al3+ ions that exhibit solar absorption and photocatalytic activity for glucose conversion to HMF in one-pot reaction, in good yield (~60%) and at moderate temperatures (80 °C). When using representative components of fulvic acid, catechol and pyrogallol as ligands, 70 and 67% HMF yields are achieved, respectively, at 70 °C. Al3+ ions are not recognised as effective photocatalysts; however, complexing them with fulvic acid components as light antennas can create new functionality. This mechanism offers prospects for new green photocatalytic systems to synthesise a range of substances that have not previously been considered.

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The iron mineral-catalyzed degradation of cephalosporin antibiotics with H2O2 occurs ubiquitously in nature. Despite numerous studies, the effects of environmental conditions on reactive species production and degradation processes of cephalosporins remain unclear. Here, we report the iron mineral of goethite as the efficient and heterogenous catalyst for the degradation of cefradine (CRD) via H2O2 activation under different conditions involving pH and visible light irradiation. Results show that the CRD removal rate is highly dependent on pH and visible light irradiation. Interestingly, when the pH ranges from 4.0 to 7.0, the degradation intermediates of CRD under dark are the same as under visible light conditions in the goethite/H2O2 system. And, the ratio of CRD degradation rate constant (kLight/kDark) reaches a maximum at pH 5.0, suggesting that CRD existing as zwitterion species is preferable for its removal with photoassistance. The mechanism investigation reveals that both •OH and ≡[FeIVO]2+ oxidants are generated during the reaction process, and •OH is the major oxidant at acidic pH, while ≡[FeIVO]2+ is more likely to be formed with photoassistance at near-neutral pH. According to UPLC-MS/MS analysis, CRD degradation likely happens via hydrogen atom abstraction from cyclohexadienyl by •OH, thioether and olefin oxidation by ≡[FeIVO]2+, and FeIII-catalyzed hydrolytic cleavage of ß-lactam ring. These findings highlight the vital roles of pH and photoassistance in the heterogeneously activated H2O2 with goethite for CRD degradation.

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A majority of clay minerals contain Fe, and the redox cycling of Fe(III)/Fe(II) in clay minerals has been extensively studied as it may fuel the biogeochemical cycles of nutrients and govern the mobility, toxicity and bioavailability of a number of environmental contaminants. There are three types of Fe in clay minerals, including structural Fe sandwiched in the lattice of clays, Fe species in interlayer space and adsorbed on the external surface of clays. They exhibit distinct reactivity towards contaminants due to their differences in redox properties and accessibility to contaminant species. In natural environments, microbially driven Fe(III)/Fe(II) redox cycling in clay minerals is thought to be important, whereas reductants (e.g., dithionite and Fe(II)) or oxidants (e.g., peroxygens) are capable of enhancing the rates and extents of redox dynamics in engineered systems. Fe(III)-containing clay minerals can directly react with oxidizable pollutants (e.g., phenols and polycyclic aromatic hydrocarbons (PAHs)), whereas structural Fe(II) is able to react with reducible pollutants, such as nitrate, nitroaromatic compounds, chlorinated aliphatic compounds. Also structural Fe(II) can transfer electrons to oxygen (O2), peroxymonosulfate (PMS), or hydrogen peroxide (H2O2), yielding reactive radicals that can promote the oxidative transformation of contaminants. This review summarizes the recent discoveries on redox reactivity of Fe in clay minerals and its links to fates of environmental contaminants. The biological and chemical reduction mechanisms of Fe(III)-clay minerals, as well as the interaction mechanism between Fe(III) or Fe(II)-containing clay minerals and contaminants are elaborated. Some knowledge gaps are identified for better understanding and modelling of clay-associated contaminant behavior and effective design of remediation solutions.

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Selective activation of the C(sp3 )-H bond is an important process in organic synthesis, where efficiently activating a specific C(sp3 )-H bond without causing side reactions remains one of chemistry's great challenges. Here we report that illuminated plasmonic silver metal nanoparticles (NPs) can abstract hydrogen from the C(sp3 )-H bond of the Cα atom of an alkyl aryl ether ß-O-4 linkage. The intense electromagnetic near-field generated at the illuminated plasmonic NPs promotes chemisorption of the ß-O-4 compound and the transfer of photo-generated hot electrons from the NPs to the adsorbed molecules leads to hydrogen abstraction and direct cleavage of the unreactive ether Cß -O bond under moderate reaction conditions (≈90 °C). The plasmon-driven process has certain exceptional features: enabling hydrogen abstraction from a specific C(sp3 )-H bond, along with precise scission of the targeted C-O bond to form aromatic compounds containing unsaturated, substituted groups in excellent yields.

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Catalytic ammoxidation of alcohols into nitriles is an essential reaction in organic synthesis. While highly desirable, conducting the synthesis at room temperature is challenging, using NH3 as the nitrogen source, O2 as the oxidant, and a catalyst without noble metals. Herein, we report robust photocatalysts consisting of Fe(III)-modified titanium dioxide (Fe/TiO2) for ammoxidation reactions at room temperature utilizing oxygen at atmospheric pressure, NH3 as the nitrogen source, and NH4Br as an additive. To the best of our knowledge, this is the first example of catalytic ammoxidation of alcohols over a photocatalyst using such cheap and benign materials. Various (hetero) aromatic nitriles were synthesized at high yields, and aliphatic alcohols could also be transformed into corresponding nitriles at considerable yields. The modification of TiO2 with Fe(III) facilitates the formation of active •O2- radicals and increases the adsorption of NH3 and amino intermediates on the catalyst, accelerating the ammoxidation to yield nitriles. The additive NH4Br impressively improves the catalytic efficiency via the formation of bromine radicals (Br•) from Br-, which works synergistically with •O2- to capture H• from Cα-H, which is present in benzyl alcohol and the intermediate aldimine (RCH═NH), to generate the active carbon-centered radicals. Further, the generation of Br• from the Br- additive consumes the photogenerated holes and OH• radicals to prevent over-oxidation, significantly improving the selectivity toward nitriles. This amalgamation of function and synergy of the Fe(III)-doped TiO2 and NH4Br reveals new opportunities for developing semiconductor-based photocatalytic systems for fine chemical synthesis.

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Direct photocatalytic CO2 reduction from primary sources, such as flue gas and air, into fuels, is highly desired, but the thermodynamically favored O2 reduction almost completely impedes this process. Herein, we report on the efficacy of a composite photocatalyst prepared by hyper-crosslinking porphyrin-based polymers on hollow TiO2 surface and subsequent coordinating with Pd(II). Such composite exhibits high resistance against O2 inhibition, leading to 12% conversion yield of CO2 from air after 2-h UV-visible light irradiation. In contrast, the CO2 reduction over Pd/TiO2 without the polymer is severely inhibited by the presence of O2 ( ≥ 0.2 %). This study presents a feasible strategy, building Pd(II) sites into CO2-adsorptive polymers on hollow TiO2 surface, for realizing CO2 reduction with H2O in an aerobic environment by the high CO2/O2 adsorption selectivity of polymers and efficient charge separation for CO2 reduction and H2O oxidation on Pd(II) sites and hollow TiO2, respectively.

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Surface-plasmon-mediated phenylacetylide intermediate transfer from the Cu to the Pd surface affords a novel mechanism for transmetalation, enabling wavelength-tunable cross-coupling and homo-coupling reaction pathway control. C-C bond forming Sonogashira coupling and Glaser coupling reactions in O2 atmosphere are efficiently driven by visible light over heterogeneous Cu and Pd nanoparticles as a mixed catalyst without base or other additives. The reaction pathway can be controlled by switching the excitation wavelength. Shorter wavelengths (400-500 nm) give the Glaser homo-coupling diyne, whereas longer wavelength irradiation (500-940 nm) significantly increases the degree of cross-coupling Sonogashira coupling products. The ratio of the activated intermediates of alkyne to the iodobenzene is wavelength dependent and this regulates transmetalation. This wavelength-tunable reaction pathway is a novel way to optimize the product selectivity in important organic syntheses.

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High-risk arsenic contamination found in aqueous system is reported across the world and causing severe environmental issues. In this study, the Mg-Al Layered Double Hydroxide (LDH) modified by sulphur species (LDH-S) was found exhibiting high effectivity and selectivity in As(V) removal owing to the strong interaction between embedded HS- and AsO43-. The LDH-S with Mg to Al ratio 2-1 give the best performance with As(V) adsorption capacity 40.8 mg/g, which is 715% higher than that of pristine LDH (2-1). The adsorbent exhibits a high tolerance to concentrated competitive anions. In the continuous flow test, the adsorbent can reduce the As(V) concentration from 20 ppm to below-ppb-level indicating the potential in industry application. The adsorption mechanism is experimentally investigated and examined by Density Function Theory (DFT) calculation. The result illustrates that, differ from the traditional ion exchange mechanism of LDH, the enhanced removal capacity and selectivity of LDH-S for As(V) is attributed to the strong affinity between H atom from HS- ion (in the interlayer region of LDH) and the O atom from AsO43-.

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Selective oxidation of alcohols is an essential reaction for fine chemical production. Here, the photocatalytic oxidation of benzyl alcohol by zinc oxide (ZnO) nanocrystals was investigated to clarify the mechanism of selective oxidation with this process. Reactivity when in contact with three distinct ZnO nanocrystal shapes: nanocones, nanorods and nanoplates, was studied in order to compare crystal facet-specific effects in the reaction system. The same non-hydrothermal and non-hydrolytic aminolysis method was used to synthesise all three nanocrystal shapes. The ZnO catalysts were characterized using by a range of techniques to establish the key properties of the prominent ZnO crystal facets exposed to the reaction medium. The ZnO nanocrystals photocatalysed the benzyl alcohol oxidation reaction when irradiated by a 370 - 375 nm LED output and each ZnO crystal morphology exhibited different reaction kinetics for the oxidation reaction. ZnO nanocones displayed the highest benzyl alcohol conversion rate while nanorods gave the lowest. This established a facet-dependent kinetic activity for the benzyl alcohol reaction of (101¯1) > (0001) > (101¯0). Experimental and density functional theory computation results confirm that the {101¯1} facet is a surface that exposes undercoordinated O atoms to the reaction medium, which explains why the reactant benzyl alcohol adsorption on this facet is the highest. Light irradiation can excite valence band electrons to the conduction band, which are then captured by O2 molecules to yield superoxide (O2•-). In a non-aqueous solvent, the photogenerated holes oxidise benzyl alcohol to form a radical species, which reacts with O2•- to yield benzaldehyde. This results in 100% product selectivity for benzaldehyde, rather than the carboxylic acid derivative.

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Gold nanoparticles (Au NPs) supported on a nanostructured gamma alumina (γ-Al2O3) fiber can exhibit excellent catalytic activity for the conversion of 5-hydroxymethylfurfural to produce its ester derivative, dimethyl 2,5-furandicarboxylate (FDMC). γ-Al2O3 was synthesized using a PEG surfactant to generate oxide fibers that randomly stack together into irregular shapes. The average particle sizes of the Au NPs are 1-6 nm, where the catalytically active Au (111) surface is the exposed facet. This 3D nanocatalyst architecture enhances the 5-hydroxymethylfurfural (HMF) oxidative esterification because HMF reactant molecules can readily diffuse into this fibrous structure and adsorb to active catalytic sites, while ester product molecules can diffuse out. Up to 99% HMF conversion and 90% FDMC selectivity can be obtained at a low reaction temperature of 45 °C, and the catalyst shows excellent recyclability. Increasing the Au content in the catalyst minimizes the requirement of a base for HMF conversion. Thus, the Au NPs supported on γ-Al2O3 can drive HMF esterification to FDMC efficiently with high product selectivity under very mild reaction conditions, omitting the need for an additional esterification step of the HMF acid.

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We report a platinum nanocluster/graphitic carbon nitride (Pt/g-C3N4) composite solid catalyst with a photocatalytic anaerobic oxidation function for highly active and selective transformation of alcohols to ketones. The desirable products were successfully obtained in good to excellent yields from various functionalized alcohols at room temperature, including unactivated alcohols. Mechanistic studies indicated that the reaction could proceed through a Pt-mediated hole oxidation initiating an α-alcohol radical intermediate followed by a two-electron oxidation pathway. The merit of this strategy offers a general approach towards green and sustainable organic synthetic chemistry.

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The practical applications of non-aqueous lithium-oxygen batteries are impeded by large overpotentials and unsatisfactory cycling durability. Reported here is that commonly encountered fatal problems can be efficiently solved by using a carbon- and binder-free electrode of titanium coated with TiO2 nanotube arrays (TNAs) and gold nanoparticles (AuNPs). Ultraviolet irradiation of the TNAs generates positively charged holes, which efficiently decompose Li2 O2 and Li2 CO3 during recharging, thereby reducing the overpotential to one that is near the equilibrium potential for Li2 O2 formation. The AuNPs promote Li2 O2 formation, resulting in a large discharge capacity. The electrode exhibits excellent stability with about 100 % coulombic efficiency during continuous cycling of up to 200 cycles, which is due to the carbon- and binder-free composition. This work reveals a new strategy towards the development of highly efficient oxygen electrode materials for lithium-oxygen batteries.

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In this study, we report a Janus- or twins-type honeycomb 3D porous nitrogen-doped carbon (NC) nanosheet array encapsulating ultrafine CoP/Co2P nanorods supported on Ti foil (CoP/Co2P@NC/Ti) as a self-supported electrode for efficient hydrogen evolution. The synthesis and formation mechanism of 3D porous NC nanosheet array assembled into a honeycomb layer with ultrafine CoP/Co2P single-crystal nanorods encapsulated is systematically presented. The CoP/Co2P@NC/Ti electrode exhibits low overpotentials (η10) of 31, 49, and 64 mV at a current density of -10 mA cm-2 in 0.5 M H2SO4, 1.0 KOH, and 1.0 M PBS, respectively, exceeding the overwhelming majority of the documented transition metal phosphide-based electrocatalysts. Density functional theory calculation reveals that the superior electrocatalytic performance for hydrogen evolution reaction could be ascribed to the strong coupling effects of the reactive facets of CoP and Co2P with the 3D porous NC nanosheet, making it exhibit a more thermo-neutral hydrogen adsorption free energy.

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Hydrotalcite materials are generally utilized for anionic pollutants due to its interlayered anion exchange ability. Their potentiality for cationic contaminants is rarely explored. In this study, disulfide (S2-) intercalated LDH material demonstrated capability to remove both heavy metal cations and oxyanions simultaneously from water. The S2- intercalation of LDH significantly improved its adsorption capability towards both heavy metal cations (Co2+ and Ni2+) and oxyanion (CrO42-). The adsorption amount of S-LDH towards Co2+ and Ni2+ reached 88.6mg/g and 76.2mg/g, which are 405% and 281% higher than that of pristine LDH. For CrO42- removal, the adsorption amount reached 34.7mg/g, 402% higher than that of pristine LDH. The cations capture mechanism mainly depends on the novel layer sheet cation substitution mechanism based on irreversible precipitation and the generation of metal sulfide precipitates. Meanwhile, the interlayered S2- can be easily replaced by CrO42- to realize the simultaneous removal of both heavy metal cations and oxyanions. In the fixed-bed column experiments, 448 bed volume (BV) (672 mL) of simulating electroplating wastewater can be efficiently treated by yielding only 1 BV(15 mL) of chemical sludge, which is practically acceptable. This work provided a highly practical adsorption technology based on the S2- modification hydrotalcite material for the purification of heavy metal ions contaminated wastewater.

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Transition-metal-doping can improve some physical properties of titanium dioxide (TiO2) nanowires (NWs), which leads to important applications in miniature devices. Here, we investigated the elastic moduli of single-crystalline pristine and Fe-doped rutile TiO2 NWs using the three-point bending method, which is taken as a case study of impacts on the elastic properties of TiO2 NWs caused by transition-metal-doping. The Young's modulus of the pristine rutile TiO2 NWs decreases when the cross-sectional area increases (changing from 246 GPa to 93.2 GPa). However, the elastic modulus of the Fe-doped rutile NWs was found to increase with the cross-sectional area (changing from 91.8 GPa to 200 GPa). For NWs with similar geometrical size, the elastic modulus (156.8 GPa) for Fe-doped rutile NWs is 24% smaller than that (194.5 GPa) of the pristine rutile TiO2 NWs. The vacancies generated by Fe-doping are supposed to cause the reduction of elastic modulus of rutile TiO2 NWs. This work provides a fundamental understanding of the effects of transition-metal-doping on the elastic properties of TiO2 NWs.

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It is challenging but important to understand the mechanical properties of one-dimensional (1D) nanomaterials for their design and integration into nanodevices. Generally, brittle ceramic nanowires (NWs) cannot withstand a large bending strain. Herein, in situ bending deformation of titanium dioxide (TiO2) NWs with a bronze/anatase dual-phase was carried out inside a transmission electron microscopy (TEM) system. An ultralarge bending strain up to 20.3% was observed on individual NWs. Through an in situ atomic-scale study, the large bending behavior for a dual-phase TiO2 NW was found to be related to a continuous crystalline-structure evolution including phase transition, small deformation twinning, and dislocation nucleation and movements. Additionally, no amorphization or crack occurred in the dual-phase TiO2 NW even under an ultralarge bending strain. These results revealed that an individual ceramic NW can undergo a large bending strain with rich defect activities.

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A carbon electrode with low cost and high stability exhibited competitiveness for its practical application in organic-inorganic hybrid perovskite solar cells (PSCs). Nonetheless, issues such as poor interface contact with an adjacent perovskite layer and obvious hysteresis phenomenon are bottlenecks that need to be overcome to make carbon-based PSCs (C-PSCs) more attractive in practice. Herein, we report an effective method to enhance the interfacial charge transport of C-PSCs by introducing the CuSCN material into the device. Two types of CuSCN-assisted devices were studied in this work. One was based on the deposition of an ultrathin CuSCN layer between the perovskite absorber layer and the carbon cathode (PSK/CuSCN/C), and the other was by infiltrating CuSCN solution into the carbon film (PSK/C-CuSCN) by taking advantage of the macroporous structure of the carbon. We have found that the CuSCN incorporation by both methods can effectively address the hysteretic feature in planar C-PSCs. The origin for the hysteresis evolution was unraveled by the investigation of the energy alignment and the kinetics of interfacial charge transfer and hole trap-state density. The results have shown that both types of CuSCN-containing devices showed improved interfacial charge carrier extraction, suppressed carrier recombination, reduced trap-state density, and enhanced charge transport, leading to negligible hysteresis. Furthermore, the CuSCN-incorporated C-PSCs demonstrated enhanced device stability. The power conversion efficiency remained 98 and 91% of the initial performance (13.6 and 13.4%) for PSK/CuSCN/C and PSK/C-CuSCN, respectively, after being stored under a high humidity (75-85%) environment for 10 days. The devices also demonstrated extraordinary long-term stability with a negligible performance drop after being stored in air (relative humidity: 33-35%) for 90 days.

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A study on the mechanical properties of one-dimensional layered titanate nanomaterials is crucial since they demonstrate important applications in various fields. Here, we conducted ex situ and in situ atomic-scale investigation on the bending properties of a kind of ceramic-layered titanate (Na2Ti2O4(OH)2) nanowire using transmission electron microscopy. The nanowires showed flexibility along the 100 direction and could obtain a maximum bending strain of nearly 37%. By analysing the defect behaviours, the unique bending properties of this ceramic material were found to correlate with a novel arrangement of dislocations, an active dislocation nucleation and movement along the axial direction resulting from the weak electrostatic interaction between the TiO6 layers and the low b/a ratio. These results provide a pioneering and key understanding on the bending behaviours of layered titanate nanowire families and potentially other one-dimensional nanomaterials with layered crystalline structures.