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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]

Utilization of visible light and the separation of electron–hole pairs is the forever theme of photocatalysis. In this work, a series of carbon quantum dots decorated bismuth oxychloride (CQDs/BiOCl) were prepared by solvothermal method, and served as photocatalysts for Rhodamine B (RhB) degradation under visible light. CQDs/BiOCl-8 (8 mL CQDs) can remove 97% RhB (20 mg/L) within 40 min, which is 11.3 times higher than pure BiOCl. This can be attributed to the fact that the excitation-independent up-conversion fluorescent characteristics of CQDs enable BiOCl to be excited by visible light. Furthermore, CQDs acted as electron libraries, which enhanced the separation of photoinduced electron–hole pairs in BiOCl. Quenching experiments confirmed that the superoxide (·O2−) and hole (h+) were main reactive oxygen species (ROS) for RhB degradation. This study provides a strategy to design highly efficient photocatalysts for environmental remediation. [ABSTRACT FROM AUTHOR]

A new strategy to realize efficient removal of organics from water through photo-self-Fenton was investigated. Characterizations and calculations demonstrated that a novel twin carbon nitride with abundant surficial N-defects and compressed π-π layer stacking can be constructed by thermal polymerization of urea under suitable basicity. Synergistically, the twins exhibited an in-situ H 2 O 2 producing at a rate as high as 26.36 mM h−1 g−1 at 420 nm that exceeded most reported C 3 N 4 , and their mineralization rates for Tetracycline Hydrochloride, Bisphenol A, Ciprofloxacin, and Rhodamine B reached 8.8, 15.2, 9.1, and 13 times higher than that of pristine C 3 N 4. It is concluded that enriching both of photogenerated electrons and molecular oxygens on specific sites plays a crucial role during photocatalysis-self-Fenton process. Particular attentions have to be paid to build structures achieving one and two-electron reduction of O 2 , and activation of H 2 O 2 to •OH simultaneously. [Display omitted] • Thermal polymerization of urea in KCl-KOH obtained a defective twin C 3 N 4. • In-situ production of H 2 O 2 and mineralization of organic pollutants through a photocatalysis-self-Fenton system. • Ingenious incorporation of compressed π–π layer stacking and surface-remodeled N-defect in carbon nitride. • Elucidation of the mechanisms for charge migration and molecular oxygen reduction. [ABSTRACT FROM AUTHOR]

In this work, Ag/AgCl/FeOCl (Ag–Fe) catalysts were successfully prepared via multistep routes in which Ag was uniformly anchored to the enriched Cl sites provided by exfoliated FeOCl nanosheets. Among these Ag–Fe catalysts, 5% Ag–Fe exhibited the highest pseudo first-order kinetic constant 0.1056 min−1 for photo-Fenton degradation of Rhodamine B (RhB), which was 11 times higher than that of FeOCl (0.0096 min−1). Ag–Fe catalysts exposed more coordinatively unsaturated Fe active sites to coordinate with H 2 O 2 due to the cleavage of Fe–Cl bond. The exposed coordinatively unsaturated Fe(III) active sites could capture the photoinduced electrons and reduce them to Fe(II), which boosted the separation efficiency of photogenerated charge carriers. Meanwhile, the photogenerated electrons of Ag0 transferred to the FeOCl, promoting the reduction of Fe(III) to Fe(II). In addition, the intensified visible light adsorption (SPR effect) was achieved after introducing Ag/AgCl nanoparticles on exfoliated FeOCl. Hydroxyl radicals (·OH) and holes (h+) were determined as the main reactive oxidative species (ROS) in the photo-Fenton degradation process. [Display omitted] • Highly dispersed of Ag/AgCl on exfoliated FeOCl nanosheets (Ag–Fe) was synthesized by a multistep method. • Enhanced photo-Fenton catalytic activity for RhB degradation was achieved under visible light. • Ag–Fe possessed rich coordinatively unsaturated Fe active sites to coordinate with more H 2 O 2. • The photogenerated electrons from Ag/AgCl accelerated the cycle of Fe(II)/Fe(III). [ABSTRACT FROM AUTHOR]

Fe-based metal organic frameworks (Fe-MOFs) being a newly developed photo-Fenton catalyst, have gained ever-increasing attention for environmental remediation, but have been limited by high synthesis cost (high energy-consumption and low yield). In this work, economical and scalable synthesis of Fe-BDC 1 (BDC denotes as terephthalic acid) was achieved via facile stirring under ambient condition, and its adsorptive, photocatalytic, Fenton-like and photo-Fenton performances were comprehensively explored against contaminants removal. In comparison, synthesized Fe-BDC 2 with the common solvothermal method, the yield of Fe-BDC 1 increased 3.4 times. Also, its adsorption capacity towards Rhodamine B (Rh. B) increased about 5.85 times. Moreover, the significantly improved degradation of Rh. B was observed in the Fenton-like and photo-Fenton systems with the increased reaction rate constants up to 4.90 and 2.33 times, respectively. This enhanced catalytic performance of Fe-BDC 1 was mainly attributed to the enlarged specific surface area (SSA) and favorable electron separation and migration, resulting into the accelerated ≡Fe(II)/≡Fe(III) cycle and increased yield of reactive oxidative species (ROSs). Additionally, the unique light-induced adsorption enhancement further strengthened the contaminants removal. Fe-BDC 1 as photo-Fenton catalyst was found superior over conventional catalysts in terms of advantages including: low dose requirement of catalysts (decrease in an order of magnitude) and H 2 O 2 , wide pH working range (3.0–9.0), excellent reusability and stability, universal removal behavior against all organic pollutants, and remarkable synergism between photocatalysis and Fenton-like process with synergistic factor of 77.23%. Moreover, the Fe coordinative unsaturated sites (Fe CUSs) and ·OH were determined as the active sites and the main ROSs, respectively, responsible for highly efficient pollutant degradation. This work gives a feasible solution for the preparation of Fe-MOFs with low synthesis cost and high yield, paving ways for their practical mass application in heterogeneous photo-Fenton oxidation. [Display omitted] • Successfully synthesis of Fe-MOFs with low cost and high yield. • Significantly enhanced adsorption, Fenton-like and photo-Fenton performances were acquired. • Visible light induced adsorption enhancement further strengthen contaminates removal. • The synergism between photocatalytic and Fenton-like process was demonstrated. • Favorable electron separation and migration accelerated ≡Fe(II)/≡Fe(III) cycle. [ABSTRACT FROM AUTHOR]

• Successful development of novel low-crystalline bimetallic MOFs as excellent photo-Fenton catalysts. • Achievement of intensified synergism between hetero-metal nodes in the low-crystalline bimetallic MOFs. • Low-crystalline state, further strengthened the role of doped metal. • The electron-rich Fe sites were formed in the low-crystalline MOFs. • Low-crystalline MOFs enable exposure of more metal CUSs, beneficial for H 2 O 2 coordination. In this study, the low-crystalline bimetallic metal-organic frameworks (MOFs) of L-MIL-53(Fe, Mn) and L-MIL-53(Fe, Cu) (MIL: Material of Institute Lavoisier) were successfully developed as photo-Fenton catalysts, exhibiting significantly enhanced degradation performance (15.2 and 2.49 times increase in reaction rate constant, respectively) for ciprofloxacin (CIP) in contrast to their crystalline counterparts. That were mainly attributed to the intensified synergism between hetero-metal nodes. Specifically, taking L-MIL-53(Fe, Mn) as an example, the formed electron-rich Fe sites along with the strengthened roles of Mn for enlarged specific surface area, enhanced visible-light absorption and separation and transportation of photo-induced carriers in the low-crystalline state, are responsible for acceleration of Fe(II)/Fe(III) and Mn(II)/Mn(III) cycles, beneficial for H 2 O 2 activation. Moreover, increased metal coordinately unsaturated sites (CUSs) are favorable for more H 2 O 2 coordination. This work gives a deep insight into the heterogeneous photo-Fenton mechanism of the bimetallic MOFs in their low-crystalline state. [ABSTRACT FROM AUTHOR]