Chlorinated volatile organic compounds (Cl-VOCs), including polychloromethanes, polychloroethanes and polychloroethylenes, are widely used as solvents, degreasing agents and a variety of commercial ...products. These compounds belong to a group of ubiquitous contaminants that can be found in contaminated soil, air and any kind of fluvial mediums such as groundwater, rivers and lakes. This review presents a summary of the research concerning the production levels and sources of Cl-VOCs, their potential impacts on human health as well as state-of-the-art remediation technologies. Important sources of Cl-VOCs principally include the emissions from industrial processes, the consumption of Cl-VOC-containing products, the disinfection process, as well as improper storage and disposal methods. Human exposure to Cl-VOCs can occur through different routes, including ingestion, inhalation and dermal contact. The toxicological impacts of these compounds have been carefully assessed, and the results demonstrate the potential associations of cancer incidence with exposure to Cl-VOCs. Most Cl-VOCs thus have been listed as priority pollutants by the Ministry of Environmental Protection (MEP) of China, Environmental Protection Agency of the U.S. (U.S. EPA) and European Commission (EC), and are under close monitor and strict control. Yet, more efforts will be put into the epidemiological studies for the risk of human exposure to Cl-VOCs and the exposure level measurements in contaminated sites in the future. State-of-the-art remediation technologies for Cl-VOCs employ non-destructive methods and destructive methods (e.g. thermal incineration, phytoremediation, biodegradation, advanced oxidation processes (AOPs) and reductive dechlorination), whose advantages, drawbacks and future developments are thoroughly discussed in the later sections.
•Chlorinated volatile organic compounds (Cl-VOCs) are ubiquitous contaminants.•The sources, human health impacts and remediation methods of Cl-VOCs are reviewed.•Future directions on risk and exposure level evaluations of Cl-VOCs are pointed.•State-of-the-art remediation technologies of Cl-VOCs are thoroughly discussed.
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A transition-metal-free approach was disclosed for intermolecular aryl C–N bonds formation between phenols and cyclic anilines via cross-dehydrogenative coupling (CDC) amination that was mediated by ...visible light, wherein K2S2O8 served as an external oxidant. The salient features of this protocol include circumventing the requirement for prefunctionalized starting materials and achieving single regioselectivity of amination adducts at room temperature.
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Highly active photocatalysts driving chemical reactions are of paramount importance toward renewable energy substitutes and environmental protection. As a fascinating Aurivillius phase material, ...Bi2MoO6 has been the hotspot in photocatalytic applications due to its visible light absorption, nontoxicity, low cost, and high chemical durability. However, pure Bi2MoO6 suffers from low efficiency in separating photogenerated carriers, small surface area, and poor quantum yield, resulting in low photocatalytic activity. Various strategies, such as morphology control, doping/defect‐introduction, metal deposition, semiconductor combination, and surface modification with conjugative π structures, have been systematically explored to improve the photocatalytic activity of Bi2MoO6. To accelerate further developments of Bi2MoO6 in the field of photocatalysis, this comprehensive Review endeavors to summarize recent research progress for the construction of highly efficient Bi2MoO6‐based photocatalysts. Furthermore, benefiting from the enhanced photocatalytic activity of Bi2MoO6‐based materials, various photocatalytic applications including water splitting, pollutant removal, and disinfection of bacteria, were introduced and critically reviewed. Finally, the current challenges and prospects of Bi2MoO6 are pointed out. This comprehensive Review is expected to consolidate the existing fundamental theories of photocatalysis and pave a novel avenue to rationally design highly efficient Bi2MoO6‐based photocatalysts for environmental pollution control and green energy development.
γ‐Bi2MoO6 has been the hotspot in the field of photocatalysis due to its distinctive intrinsic properties. This Review summarizes recent modulation strategies and major photocatalytic applications of γ‐Bi2MoO6. Importantly, the current research status and the challenges and potentials of this material are also highlighted. The aim is to pave a novel avenue to rationally design highly efficient Bi2MoO6‐based photocatalysts.
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A general electrochemical system for reductive hydrodefunctionalization is described, employing the inexpensive and easily available triethylamine (Et
3
N) as a sacrificial reductant. This protocol ...is characterized by facile operation, sustainable conditions, and exceptionally wide substrate scope covering the cleavage of C-halogen, N-S, N-C, O-S, O-C, C-C and C-N bonds. Notably, the selectivity and capability of reduction can be conveniently switched by simple incorporation or removal of an alcohol as a co-solvent.
A facile electro-reductive hydrodefunctionalization system employing triethylamine as a sacrificial reductant is described, and the selectivity and capability of reduction can be conveniently switched by simple change of the reaction solvent.
Compared with general redox chemistry, electrochemistry using the electron as a potent, controllable, yet traceless alternative to chemical oxidants/reductants usually offers more sustainable options ...for achieving selective organic synthesis. With its environmentally benign features gradually being uncovered and studied, organic electrosynthesis is currently undergoing a revival and becoming a rapidly growing area within the synthetic community. Among the electrochemical transformations, the anodically enabled ones have been far more extensively exploited than those driven by cathodic reduction, although both approaches are conceptually attractive. To stimulate the development of cathodically enabled organic reactions, this review summarizes the recently developed reductive electrosynthetic protocols, discussing and highlighting reaction features, substrate scopes, applications, and plausible mechanisms to reveal the recent trends in this area. Herein, cathodic reduction-enabled preparative organic transformations are categorized into four types: reduction of (1) unsaturated hydrocarbons, (2) heteroatom-containing carbon-based unsaturated systems, (3) saturated C-hetero or C–C polar/strained bonds, and (4) hetero-hetero linkages. Apart from net electroreductive reactions, a few examples of reductive photo-electrosynthesis as well as paired electrolysis are also introduced, which offer opportunities to overcome certain limitations and improve synthetic versatility. The electrochemically driven, transition metal-catalyzed reductive cross-couplings that have been comprehensively discussed in several other recent reviews are not included here.
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•Comprehensive summary of the advancements made in the field of reductive organic electrosynthesis since 2017.•Perspectives on the current trends, challenges, and opportunities in cathodic reduction-enabled organic electrosynthesis.•Suggestions for the development of efficient, sustainable, and practical reductive protocols in organic electrosynthesis.
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Metal organic frameworks (MOFs), as an original kind of organic–inorganic porous material, are constructed with metal centers and organic linkers via a coordination complexation reaction. Among ...uncountable MOF materials, iron‐containing metal organic frameworks (Fe‐MOFs) have excellent potential in practical applications owing to their many fascinating properties, such as diverse structure types, low toxicity, preferable stability, and tailored functionality. Here, recent research progresses of Fe‐MOFs in attractive features, synthesis, and multifunctional applications are described. Fe‐MOFs with porosity and tailored functionality are discussed according to the design of building blocks. Four types of synthetic methods including solvothermal, hydrothermal, microwave, and dry gel conversion synthesis are illustrated. Finally, the applications of Fe‐MOFs in Li‐ion batteries, sensors, gas storage, separation in gas and liquid phases, and catalysis are elucidated, focusing on the mechanism. The aim is to provide prospects for extending Fe‐MOFs in more practical applications.
Iron‐containing metal organic frameworks (Fe‐MOFs) have attracted intensive attention due to their unique topological structure and exploitable properties. Owing to the functional applications in electrochemical devices and its adsorbent and photo‐electrocatalyst properties, Fe‐MOFs have become an emerging hot topic for high‐performance energy conversion devices, gas/liquid separation, and advanced catalysis.
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•Hollow N/Co codoped carbon spheres are successfully prepared.•PS@bimetal-ZIFs are synthesized and used as the sacrifice templates.•The structure properties of Co-HNCS can be well ...regulated.•The optimal catalyst is a promising candidate for oxygen reduction reaction.
To explore efficient non-noble metal-based electrocatalysts for oxygen reduction reaction (ORR), herein we developed a facile bottom-up approach for the fabrication of a hollow porous carbon sphere codoped with ultra-small Co nanoparticles and uniform nitrogen distribution (Co-HNCS) via one-step pyrolysis of a core-shell type precursor composing of polystyrene (PS) core and bimetallic ZIF (zeolite imidazolate framework) shell. The bimetallic Co-Zn-ZIFs (BMZIFs) was selected as the sacrifice template due to not only its high nitrogen content and regular porosity but also the superiority that Zn species in BMZIFs can both spatially separate Co species to suppress the aggregation of ultra-small Co NPs and be evaporated to afford extra pores during high-temperature pyrolysis. As expected, by adjusting the starting molar ratio of Zn to Co, we were able to prepare Co-HNCS-x (x represent the molar ratio of Co to total starting metal feeding) that exhibited unique hollow structure with large surface areas, enhanced mass transport, high porosities, tunable particle sizes and graphitization degrees, abundant highly active CoNx sites, and thus significantly improved ORR performance. Particularly, the optimal Co-HNCS-0.2 exhibited the remarkable ORR activity (the onset and half-wave potentials were 0.94 and 0.82Vvs. RHE, respectively) via an efficient four-electron-dominant ORR process in alkaline medium, which outperformed that of commercial Pt/C (20wt%, the onset and half-wave potentials were 0.93 and 0.80Vvs. RHE, respectively) and most of previously reported Co-based catalysts. Moreover, it also displayed much superior stability and tolerance to methanol as compared to Pt/C, further highlighting the merit of this facile synthesis approach. Our findings might inspire new thoughts on the development of precious-metal-free, highly-efficient and cost-effective ORR electrocatalysts derived from MOF.
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Here we describe a straightforward and efficient approach for regiospecific introduction of an allyl group into cycloalkanol molecules employing a visible-light-mediated ring-opening strategy. A wide ...range of distally allylated or formylated ketones is furnished from 1-aryl cycloalkanol precursors of variable ring sizes, providing a concise and practical access for the modification of complex natural products. Preliminary mechanistic studies demonstrate that the key O-centered radicals mediate the sequential ring cleavage and allylation/formylation.
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The possibility of using inner cavities within metal-organic frameworks (MOFs) as templates for the fabrication of tiny metal nanoparticles (NPs) was attempted in this work. An unprecedented design ...of Pd@Ag core-shell NPs on MOFs
a seed mediated growth strategy is reported and attributed to the presence of activated physisorbed hydrogen atoms on embedded Pd NPs as reducing agents to selectively direct the deposition of Ag onto Pd while minimizing the Ag self-nucleation. The obtained Pd@Ag core-shell NPs exhibited a significant increase in selectivity in the partial hydrogenation of phenylacetylene as compared to their monometallic counterparts, due to the surface dilution and electron modification of the surface Pd sites by Ag deposition. Pd@Ag NPs also possessed an unprecedented high stability and recyclability in the catalytic reactions, related to the nano-confinement effect and the strong metal-support interaction offered by the MOF framework.
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