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Pyridinic nitrogen vacancy in carbon nitride for photo-self Fenton-like purification of organic contaminants. [Display omitted] • Carbon nitride with pyridinic nitrogen vacancy was successfully prepared. • Pyridinic nitrogen vacancy promotes charge transfer and activating O 2 into H 2 O 2. • Pyridinic nitrogen vacancy accelerates carbon nitride to adsorb organic contaminants. • Photo-self Fenton-like reaction for photocatalytic degradation of organics. This work reports a carbon nitride with pyridinic nitrogen-vacancy (N 2C V-CN), which purifies organic contaminants via an in-situ photo-self Fenton-like reaction. Experiments and calculations demonstrated that the nitrogen-vacancy induces lone-paired (LP) and symmetry-unpaired electrons, promoting the formation of low-energy LP-π hybridized orbitals and helping to overcome the pairing energy required for oxygen to accept electrons. Furthermore, the nitrogen-vacancy accelerates film and intra-particle diffusion rates of organic contaminants on N 2C V-CN, creating beneficial conditions for reactive oxide species to mineralize organic contaminants. Under sunlight and atmospheric oxygen, a photo-self Fenton-like reaction involving proton-coupled electron transfer occurred on the surface of N 2C V-CN. Furthermore, by integrating photocatalysis with flocculation, about 99.1 % suspended substance, 45.5 % chemical oxygen demand, and 38.4 % biological oxygen demand were reduced from polluted river-water. Constructing N 2C V-CN and understanding its crucial role offer theoretical and methodological insights into the in-situ purification of contaminated water bodies. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Nδ− → Wδ+ coordinate-covalent bonds construct an intimate S-scheme heterojunction in WO 3 /CN. • H 2 O 2 produced in-situ by hole-water oxidation and electron-oxygen reduction reactions. • A coupling of Ciprofloxacin removal and H 2 O 2 production during photocatalysis. • Experiments and DFT calculations revealed the processed in utilizing solar energy and molecular oxygen for water decontamination. Photo self-Fenton catalyst is a promising candidate for solar energy conversion and environmental remediation. Here we reported a Tungsten trioxide/carbon nitride (WO 3 /CN) in which the surficial amino groups on CN are inserted into the WO 3 matrix, forming coordinate covalently Nδ− → Wδ+ in construction of an intimate S-scheme heterojunction. The intimantance promotes the transfer of photocarriers under light irradiation. The nanohybrids produced hydrogen peroxide (H 2 O 2) in a rate about 20 times of pristine CN. A dual-path architecture in which H 2 O 2 are produced via hole-water oxidation and electron-oxygen reduction was poposed. It is founded that ciprofloxacin also involved in production of H 2 O 2 by their deprotonation to superoxide anions, and holes and hydroxyl radicals effectively attack the weak sites in skeleton of ciprofloxacin. This work suggests a great significance of strategy in self-producing of H 2 O 2 in utilizing solar energy and molecular oxygen for water, particularly the surface water decontamination. [ABSTRACT FROM AUTHOR]

Three existent states of carbon were introduced in FeOCl, namely graphite carbon, carbon dots and lattice carbon. The excellent photo-Fenton performance of C-FeOCl were attributed to the exposure of CUISs on the inner/outer surfaces of FeOCl and the efficient transportation-separation of photogenerated electrons in the horizontal and vertical directions of FeOCl. [Display omitted] The photo-Fenton process is promising for sincerely treating contaminated water. In this work, carbon-decorated iron oxychloride (C-FeOCl) is synthesized as a photo-Fenton catalyst for removing tetracycline (TC) from water. Three actual states of carbon are identified and their different roles in enhancing photo-Fenton performance are revealed. All carbon on/in FeOCl, including graphite carbon, carbon dots and lattice carbon, enhance visible light adsorption. More importantly, a homogeneous graphite carbon on the outer surface of FeOCl accelerates the transportation-separation of photo-excited electrons along the horizontal direction of FeOCl. Meanwhile, the interlayered carbon dots offer a Fe O C bridge in helping the transportation-separation of photo-excited electrons along the vertical direction of FeOCl. In this way, C-FeOCl acquires isotropy in conduction electrons to ensure an efficient Fe(II)/Fe(III) cycle. These interlayered carbon dots extend the layer spacing (d) of FeOCl to about 1.10 nm, exposing the internal iron centers. The lattice carbon significantly increases the amounts of coordinatively unsaturated iron sites (CUISs) in activating hydrogen peroxide (H 2 O 2) to hydroxyl radical (OH). Density functional theory (DFT) calculations confirm this activation on inner and external CUISs with a significantly low activation energy of about 0.33 eV. [ABSTRACT FROM AUTHOR]

[Display omitted] • Successful introduction of NCDs in different existent sites of TNTs via a facile synthesis. • Different roles played by NCDs-IT and NCDs-OT enhanced the performance of TNTs toward simultaneous removal of Cu2+ and NOR. • Outstanding photocatalytic performance of NCDs-TNTs benefited from synergies between NCDs-IT and NCD-OT. • Self-synchronous doping of adsorbed Cu2+ further promoted the oxidation of NOR on NCDs-TNTs. • Probable degradation pathways of NOR were deduced through the combination of 3D EEMs and MS. In this work, nitrogen-doped carbon dots (NCDs) were introduced in different existent sites of titanate nanotubes (TNTs) by a facile synthesis, and their effects on surface potential, photoelectrochemical properties and simultaneous removal of coexisted Cu2+ and norfloxacin (NOR) performance in water were systematically investigated. Constructed NCDs-TNTs composite displayed superior performance towards the adsorption (ion exchange/coordination) of Cu2+ and adsorption-oxidization of NOR over the two individuals, mainly benefiting from the collaboration of NCDs in different existent states. The existence of Ti N H chemical linkage was identified between TNTs and NCDs-OT (NCDs on the outer surface of TNTs), which not only modulates the surface potential to favor the external diffusion of Cu2+ or NOR+ from aqueous solution to the negatively charged NCDs-TNTs, but also facilitates the intraparticle transfer of contaminants to the reactive sites. In addition, the up-conversion light property of NCDs-OT and the interstitial NCDs-IT (NCDs on the inner surface of TNTs) doping in TNTs interact together to enable NCDs-IT-TNTs to fully absorb and utilize all visible light. The photoexcited electrons were further trapped by NCDs-OT to promote the photogenerated carrier separation. Adsorbed Cu2+ could also improve the performance of NCDs-TNTs toward NOR oxidization, mainly owing to the self-synchronous doping of adsorbed Cu2+ broadening light absorption area and acting as mediators for delivering electrons. This work provides unique insights into the structural design of composite materials for such combined contamination remediation in water. [ABSTRACT FROM AUTHOR]

Photocatalytic process of Bi 0.8 Mn 0.2 OBr for CV degradation. [Display omitted] • The Mn-doping BiOBr generated intermediate state in band gap. • Oxygen vacancies and Mn-doping synergistic ameliorating separation of the photo-generated charge. • The intermediate energy states and oxygen vacancies play important role in charge separation. • DFT calculation confirmed the oxygen vacancies beneficial to molecular oxygen activation. • The in-depth mechanisms insight of charge separation and molecular oxygen activation. High-efficiency separation of photogenerated charges and molecular oxygen activation is very important for photocatalytic removal of organic pollutants. However, the current understanding of the effect mechanism of metal substitution for the separation of photo-generated charges and molecular oxygen activation is still poor. Herein, efficient manganese (Mn)-doped BiOBr hollow microspheres synthesis, systematic characterizations, and theoretical calculation discovered that Mn-doping could not only induce produce oxygen vacancies (OVs), but also can act as active sites for catalytic reactions. The induced production of OVs and Mn2+/Mn3+ by Mn optimal doping introduced into BiOBr can synergistic promote the separation of photogenerated charges and molecular oxygen activation leads to significantly enhances degradation of crystal violet (CV). Upon analysis, Mn-doping introducing unsaturated d-orbital with bridging O2– formation π-donation accelerated the separation of photo-generated charges. Meanwhile, the larger overlap of Mn-3d orbitals with O 2 -2p orbitals forms a π-donation bond with charge transfer from metal to O 2 leading to the oxygen–oxygen (O O) bond length and molecular oxygen activation. Finally, we proposed a possible mechanism to explain the highly efficient photocatalytic degradation performance of the acquired photocatalysts. This study provides not only a novel strategy for the rational design of highly active photocatalysts, but also in-depth insights into the separation of photo-generated charges and molecular oxygen activation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Successful development of bimetallic MOFs with ligand missing defects as excellent photo-Fenton catalysts. • Regulating Lewis acidity for more H 2 O 2 active sites. • Tuning local electron density of Fe sites to promote the conversion of H 2 O 2. • Lower activation energy barrier between H 2 O 2 and active sites. The photo-Fenton performance of Fe-based metal organic frameworks (Fe-MOFs) largely depends on the amount and the local electron density of metal coordinately unsaturated sites (M CUSs). However, a majority of Fe active sites are fully bound by organic ligands leading to decreased Fe CUSs. Additionally, the symmetrical electronic distribution of iron-oxo (Fe-O) clusters and the fast electron-hole recombination are unbeneficial for the directional electron transfer and the following electron accumulation on Fe CUSs. Herein, the structure of Fe-O clusters onto the framework of MIL-88B was controllably regulated via change of Ce doping amount, among which Fe 0.8 Ce 0.2 -MIL-88B exhibited highest removal efficiency of tetracycline (TC). That was mainly ascribed to the following two points: for one, the induced ligand missing defects ameliorated the pore structures and generated more M CUSs; for another, the lower electronegativity of Ce than Fe and the role of ligand missing defects as electron trap state collectively increased the local electron density at Fe CUSs. As a result, the increased M CUSs provided more active sites for H 2 O 2 coordination and the highly concentrated electrons density at Fe CUSs afforded the substantial electron donation towards robust H 2 O 2 dissociation into ∙OH. Furthermore, the increased mesoporous size favored highly-efficient utilization of ∙OH. This work provides a facile strategy to improve photo-Fenton performance of Fe-MOFs. [ABSTRACT FROM AUTHOR]