Latest ArticlesGraphitic carbon nitride (g-C3N4) has been widely studied as a visible light responsive photocatalyst in recent years, due to its facile synthesis, low cost, high stability, and appropriate bandgap/band positions. In this review, we firstly introduce and compare various exfoliation approaches of bulk g-C3N4 into ultrathin g-C3N4 nanosheets. Then, many modification strategies of g-C3N4 nanosheets are also reviewed, including heterojunction construction, doping, defect control, and structure design. Thereafter, the charge transfer mechanism in g-C3N4 nanosheets based heterojunctions is present, e.g., Z-scheme, S-scheme and other forms. Besides, the photocatalytic applications of g-C3N4 nanosheets based photocatalysts are summarized including environmental remediation, energy generation and storage, organic synthesis, and disinfection. This review ends with a summary and some perspectives on the challenges and new directions in exploring g-C3N4 nanosheets-based photocatalysts.
Selective oxidation of biomass-derived monosaccharide into high value-added chemicals is highly desirable from sustainability perspectives. Herein, we demonstrate a surface-functionalized carbon nanotube-supported gold (Au/CNT-O and Au/CNT-N) catalyst for base-free oxidation of monosaccharide into sugar acid. Au/CNT-O and Au/CNT-N surfaces successfully introduced oxygen- and nitrogen-containing functional groups, respectively. The highest yields of gluconic acid and xylonic acid were 93.3% and 94.3%, respectively, using Au/CNT-N at 90 ℃ for 240 min, which is higher than that of using Au/CNT-O. The rate constants for monosaccharide decomposition and sugar acid formation in Au/CNT-N system were higher, while the corresponding activation energy was lower than in Au/CNT-O system. DFT calculation revealed that the mechanism of glucose oxidation to gluconic acid involves the adsorption and activation of O2, adsorption of glucose, dissociation of the formyl C-H bond and formation of O-H bond, and formation and desorption of gluconic acid. The activation energy barrier for the glucose oxidation over Au/CNT-N is lower than that of Au/CNT-O. The nitrogen-containing functional groups are more beneficial for accelerating monosaccharide oxidation and enhancing sugar acid selectivity than oxygen-containing functional groups. This work presents a useful guidance for designing and developing highly active catalysts for producing high-value-added chemicals from biomass.
Lithium-halogen batteries (LHBs), including lithium iodide (Li-I2) and lithium bromide (Li-Br2) batteries, are receiving more attention for offering high energy density and excellent kinetic performance. However, LHBs commercialization is seriously hindered by the high solubility of halides, causing lower capacity and poor cyclability. This research covers the fabrication of a highly stable cathode of amorphous carbon coated CMK-3/LiI/LiBr nanocomposite for metal lithium batteries. The nanopores and coated layer can physically trap the dissolution of active materials. The amorphous carbon generated from polyacrylonitrile carries abundant nitrogen heteroatoms for the stable anchorage of halogens and halides via strong chemical adsorption. In addition, iodine can act as a complexing agent with bromine to reduce solvation energy. Consequently, the as-prepared CMK-3/LiI/LiBr/carbon (CIBP) nanocomposite cathode demonstrates an ultra-high reversible capacity of 407.4 mAh/g at the current density of 1.0 C performing up to 300 stable cycles.
Li-ion batteries with solid polymer electrolytes (SPEs) are safer than conventional liquid electrolytes due to the absence of highly flammable liquid electrolytes. However, their performance is limited by the poor Li+ transport in SPEs at room temperature. Anion-containing polymer-chains incorporated SPEs (ASPEs) are therefore developed to enhance Li+ diffusion kinetics. Herein, we propose a novel and feasible strategy to incorporate the anion-containing polymer-chains, such as lithiated perfluorinated sulfonic acid (PFSA), into polyvinylidene fluoride (PVDF) polymer-based SPEs. The immobile anion groups from the PFSA-chains impede the migration of mobile anion groups dissociated from the Li salt. The transference number is thus raised from ~0.3 to 0.52 with the introduction of anion-containing polymer-chains into SPEs. The electrostatic repulsion among anion-containing chains also reduces the close chain stacking and brings 159% increase in the ionic conductivity to 0.83 × 10−3 S/cm at 30 ℃ in contrast with the pure PVDF-based SPE. In addition, LiFeO4/Li batteries with ASPEs exhibit 55% capacity boost at 0.5 C in contrast to the capacity of batteries with pure-PVDF SPEs, and also offer more than 1000 charge/discharge cycles. Our research findings potentially offer a facile strategy to design thermal stable SPEs with superior Li+ transport behaviors towards developing high-performance SPEs-based batteries.
Electrochromic devices (ECDs) have exhibited promising applications in the fields of energy-saving intelligent buildings and next-generation displays because of their simple structure, low power consumption, and multicolor displays. W18O49/polyaniline (PANI) hybrid films are prepared and assembled to ECDs. Compared with pure PANI and W18O49 films, the hybrid film exhibits superior electrochemical and electrochromic performance, including high optical modulation (70.2%), large areal capacity (79.6 mF/cm2), and good capacitance retention. The excellent electrochemical and electrochromic performance is ascribed to the formation of the donor (PANI)-acceptor (W18O49) pair, the porous structure in the nanowires, and the large surface area, which enhance electron delocalization of the W18O49/PANI, improve the ion diffusion rate, and increase the charge storage sites. Furthermore, benefitting from the outstanding optical, electrical, and multifunctional properties, the W18O49/PANI hybrid film-based ECD platform is expected to play an important role in electrochromism and energy storage.
Benzene is a volatile organic compound that can seriously harm human health, while it can serve as a precursor to produce chemicals of more complex structures in chemical industry. Capturing benzene using adsorbents is of great importance for human health, when the separation of hydrocarbons including benzene from crude oil was referred to as one of the “seven chemical separations to change the world”. In this work, we reported the efficient and selective separation of benzene from BTX and cyclohexane by hydrogen bonding self-assembly nonporous adaptive crystals AdaOH for the first time under mild and user-friendly conditions. Separation of benzene and cyclohexane (v/v = 1:1) can be achieved by AdaOH with a purity of benzene up to 96.8%. Separation of BTX (v/v; benzene:toluene:o-xylene:m-xylene:p-xylene= 1:1:1:1:1) can be achieved by AdaOH with a purity of benzene increased from 20% to 82.9%. Our results suggest that separation of benzene using the activated AdaOH as a non-porous adaptive crystal for selectively and efficiently capturing benzene can solve the challenge in separation of benzene from other chemicals such as cyclohexane in chemical industry, and can be helpful for removal of benzene that is released from the vehicles to air. The advantages of commercially availability, easy preparation, high separation efficiency and selectivity for benzene might endow this material with enormous potential for practical uses in areas like petrochemical industry.
Palladium-catalyzed cycloaddition reactions via Pd-π-allyl zwitterions have been established as significant synthetic transformations to enable numerous carbon- or heterocycles compounds that are key constituents of various biologically active natural products and pharmaceuticals. In addition to the well-known Pd-π-allyl zwitterions,including palladium-trimethylenemethane and Pd-1,3/1,4-zwitterions,chemists have recently discovered new applications of several long ago reported but less-studied Pd-π-allyl zwitterions,which can straightforwardly and efficiently construct novel cyclic architectures. Meanwhile,some impressive newly designed zwitterions have been also developed. Those zwitterions are diverse and can serve as transient and highly reactive intermediates for the subsequent cyclization with various acceptors. In this review,we highlight recent advances in applications of these two types of zwitterions in the synthesis of complex polycyclics and medium-sized cyclic compounds.
Oxygen-isotopic labelings play important roles in identifying and understanding chemical and biological processes. Direct C=O to C=18O or C=17O conversion in a single step leading to labeled compounds can alleviate synthetic burdens without the need for resynthesis. Here we describe a photocatalytic oxygen-isotopic labeling protocol that can efficiently and selectively install 18O and 17O on carbonyls of ketones and aldehydes via oxygen isotope exchange with oxygen-isotopic waters (H218O or H217O) as the sources of oxygen isotopes, in which light and oxygen-enabled sodium alkanesulfinates catalyzed this process. This strategy was extended to the in-situ formed ketones from the photocatalytic aerobic oxidation of alkyl arenes and secondary alcohols. Furthermore, reduction of the oxygen-isotopically labeled aldehydes with NaBH4 provided the corresponding oxygen-isotopically labeled primary alcohols. We believe that the oxygen-isotopically labeling method will be widely used in chemistry, biology and medicine fields.
An eco-friendly and convenient method is developed herein for the synthesis of S-aryl dithiocarbamates via visible-light-induced SET process of an EDA complex between thianthrenium salt functionalized arenes and dithiocarbamate anions under mild aqueous micellar conditions. This strategy indirectly realizes the method for constructing S-aryl dithiocarbamates through site-selective C−H functionalization of arenes. Most importantly, the reaction proceeded smoothly without addition of any photocatalyst, and the by-product thianthrene is recycled in quantity, ultimately minimizing the production of chemical waste. This protocol provides a promising synthesis candidate for the construction of valuable S-aryl dithiocarbamates, which also opens up a new avenue for micellar photocatalysis.
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