Latest ArticlesNanodiamond (ND) has long been recognized as an effective carbocatalyst for synthesizing styrene via direct dehydrogenation (DDH). However, the induced drastic pressure drop of its powder form limits its industrial application in heterogeneous catalytic process. In this work, we report a facile hexamethylenetetramine nitrate (HN)-assisted thermal impregnation (HNTI) strategy for fabricating a novel nanodiamond-based monolithic foam (ND/CNT-SiC-ms-HN) catalyst through a two-step approach: One is to soak the carbon nanotube-modified SiC foam (CNT-SiC) with the slurry composed of HN, KCl, LiCl, and dispersed ND, and the other is to heat the slurry-soaked CNT-SiC (ND-HN-KCl-LiCl/CNT-SiC) in N2 atmosphere at 750 ℃. The as-synthesized ND/CNT–SiC-ms-HN monolithic foam features the enriched surface kenotic CO by promoted ND dispersion and O-doping, abundant stuctural defects, and improved nucleophilicity by N-doping, originating from the promoted ND dispersion by thermal impregnation (TI) in KCl-LiCl molten salt (MS) and the presence of HN in the annealing process. As a result, the ND/CNT–SiC-ms-HN monolithic foam catalyst by HNTI strategy exhibits 1.5 folds higher steady-state styrene rate (5.49 mmol g−1 h−1) associated with 98.4% of styrene selectivity compared to the ND-based monolithic foam catalyst (ND/CNT-SiC). Moreover, the ND/CNT–SiC-ms-HN monolithic foam shows excellent long-term stability for the direct dehydrogenation of ethylbenzene to styrene. This work also comes up with a novel way of preparing other highly-dispersed nanocarbons-based monolithic foam catalysts with promising catalytic performance for diverse transformations.
Benefiting from the large Stokes shift between fluorescence and phosphorescence, fluorescence/phosphorescence dual-emitting carbon dots (CDs) have gradually entered at the stage of single-phase white light-emitting diodes (WLEDs) as 'green material'. However, most of the developed dual-emitting CDs have weak phosphorescence, short emission wavelength and narrow emission band, resulting in relatively bluish white light emission and low color rendering index (CRI). Herein, an ultrabroad-band fluorescence/phosphorescence dual-emitting CD-based material (UB-CD@BA) is prepared by thermal treatment of boric acid (BA) and CDs with large conjugated structure. The stable covalent bonding between CDs and BA, as well as three-dimensional spatial restriction effect of self-polymerization BA molecules around CDs during long-term heating efficiently rigidified the single/triplet excited states of CDs from non-radiative deactivation, thus producing strong dual emissive materials with the high phosphorescence quantum yield of 21%. Remarkable, the prepared UB-CD@BA powders exhibit bright pure white light emission with Commission Internationale de l'Eclairage (CIE) coordinates of (0.32, 0.33) and the highest reported full width at half maximum of 250 nm. Based on the unique characteristics of UB-CD@BA, it was used as a color conversion layer to prepare a WLED with CIE coordinates of (0.35, 0.33) and the CRI value of 87.
Photocatalytic oxidative desulfurization (PODS) over efficient earth-abundant catalysts to obtain clean fuel oil is of great importance for the environmental protection. In this work, a series of Ce-doped MIL-125-NH2 photocatalysts were successfully prepared via a simple in-situ doping method and exhibited superior PODS performance of dibenzothiophene (DBT) under mild reaction conditions. The 1.0 mol% Ce/MIL-125-NH2 catalyst achieved 100% sulfur removal within 22 min at 30 ℃ under visible light illumination, which is mainly attributed to the high surface area and the formation of Ce-Ti-oxo clusters due to electronic coupling. The valence transformation of Ce4+/Ce3+ and Ti4+/Ti3+ redox mediators could not only expose abundant Lewis acid sites, but also promote the separation and transfer of photogenerated charges. In addition, increasing the reaction temperature has been demonstrated to be effective in promoting the PODS performance. Additionally, a thermo-enhanced PODS mechanism was proposed over Ce/MIL-125-NH2, demonstrating the great potential of thermal energy to promote the desulfurization activity.
In recent years, Fe3O4 nanomaterials have received much attention in analytical chemistry due to their excellent magnetic and peroxidase-like activity. As the catalytic characteristics of Fe3O4 nanomaterials is similar to those of horseradish peroxidase (HRP), Fe3O4 nanomaterials are also used as peroxidase mimics and have achieved a certain development in many fields based on latest research results. To improve the stability and catalytic ability of simple Fe3O4 nanomaterials, various modification strategies of Fe3O4 nanomaterials have been developed. The recent advances of these strategies have been presented and discussed. In addition, this paper introduces the application of Fe3O4 nanozymes in the detection of food and industrial pollutants, as well as in the field of biosafety.
Vascularization and bone regeneration are closely related in the process of bone remodeling, and designing a bioactive scaffold with pro-angiogenic and osteogenic properties may accelerate the repair of bone defects. In this work, an iron-based metal–organic framework (MIL-88) was developed as a carrier for loading a pro-angiogenic small molecular drug (dimethyloxallyl glycine, DMOG), and then embedded into the PLGA nanofibrous scaffolds to repair cranial defects in rats. Imaging and histological evaluation indicated that PLGA/MIL@D scaffold markedly enhanced vascularization and bone regeneration in vivo. Moreover, in vitro assay showed that co-delivery system significantly promoted angiogenesis by stimulating endothelial cell migration, tube formation, and enhanced osteogenesis by promoting expression of osteoblast related proteins. In addition, PLGA/MIL@D scaffold promotes angiogenesis by activating the hypoxia-inducible factor-1 (HIF-1)/vascular endothelial growth factor (VEGF) signaling pathway. Altogether, this bioactive PLGA/MIL@D scaffold can combine angiogenesis with osteogenesis, and will be a bright strategy for the repair of bone defects.
An unprecedent [4 + 3] cycloaddition of furoketenimines with furocarbenoids has been disclosed for the divergent and efficient synthesis of cycloheptafuran and cycloheptapyrrole scaffolds. Zinc chloride acted as promoters for both the formation of these two transient intermediates from isocyanides and ene-yne-ketones, and the subsequent construction of seven-membered ring. Three rings and five bonds were constructed successively in this three-component one-pot domino reaction.
Owing to its outstanding photoactivity, ferrioxalate is originally used as an actinometer and subsequent work has discovered that photochemistry of ferrioxalate is also fundamentally or technically important in atmospheric chemistry and water treatment. While the overall products generated from photolysis of ferrioxalate are known to include Fe(Ⅱ), a series of oxidizing (e.g., •OH, O2•−/HO2•−) or reducing (C2O4•−/CO2•−) radicals and H2O2, however, at the molecular level, the primary step of the photoreaction of ferrioxalate remains as an unsolved mystery due to the difficulty in examining such ultrafast processes. Benefiting from the development of time-resolved spectroscopy, this old question has been studied with increasing vigor recently, by means of such ever-more-sophisticated techniques (e.g., flash photolysis, time-resolved X-ray absorption spectroscopy (XAS), femtosecond infrared (IR) absorption spectroscopy, ultrafast photoelectron spectroscopy (PES)). There are two contrary views on the primary reaction mechanism: (1) Intramolecular electron transfer (ET) precedes the cleavage of the metal-ligand bond; (2) The dissociation of C–C or Fe–O bond occurs before intramolecular ET. Thus, this review presents a comprehensive summary about the overall reaction mechanism and molecular level mechanism of ferrioxalates. In chronological order, we have elaborated two predominant but controversial views from the perspectives of different experimental approaches. Some challenges and research opportunities in this active field are also briefly discussed.
In the present work, a stable two-dimensional (2D) P2Si monolayer was predicted. The monolayer is semimetallic/metallic under the PBE/HSE06 functional and is mechanically isotropic. The stability of the P2Si monolayer has been proved via cohesive energy, mechanical criteria, molecular dynamics simulation, and phonon dispersion respectively, and the monolayer possesses high carrier mobility which is three times that of MoS2. On the other hand, the catalytic performance of the P2Si monolayer modified with a single transition metals (M = Sc-Cu) atom for the electrochemical reduction of CO2 was investigated, and the monolayer can catalyze CO2 with three constraints: stable molecular dynamics, high migration potential of metal atoms, and suitable band gap for electrocatalyst after metal doping exhibiting excellent catalytic stabilization activity and CRR selectivity. In addition, the reduction product of V@P2Si is HCOOH with an overpotential as low as 0.75 V, and the most suitable reaction path is *CO2 → *CHOO → O*CHOH → * + HCOOH with the final reduction product HCOOH obtained. As a whole, the above results endow the P2Si monolayer to be a good 2D material holding great promises for applications in nanoelectronics and CO2 reduction catalysts.
Benzimidazoles are very important chemical materials in the pharmaceutical industry, and the most common synthetic route is cyclization of o-phenylenediamine with carbon sources, in which utilization of inexpensive and abundant CO2 as C1 source is very impressive. Porous aromatic frameworks (PAFs) with highly desired skeletons have attracted great attentions in gas capture and catalysis. Herein, B-based PAF-165 and PAF-166 are designed and synthesized via Friedel-Crafts alkylation reaction, which present high surface areas as well as high stability. Benefiting from the abundant electron-deficient B centers, both PAFs exhibit excellent selective CO2 adsorption abilities. The presence of sterically hindered B units in PAFs can act as Lewis acid active sites for the frustrated Lewis pairs (FLPs) in situ formation with o-phenylenediamine, thus promoting the synthesis of benzimidazole. The optimal reaction conditions for o-phenylenediamine cyclization with PAF catalysts are explored, and the reaction mechanism is also proposed. This work provides feasible ideas for incorporating FLPs within porous materials as reusable heterogeneous catalysts for CO2 capture and conversion.
Coating inorganic ceramic particles on commercial polyolefin separators has been considered as an effective strategy to improve thermostability of separator. However, the introduction of the coating layer could induce pore blockage on the surface of the polyolefin separator. Herein, a ceramic composite layer that consists of alumina nanoparticles (n-Al2O3) and halloysite nanotubes (HNTs) is designed to modify the polyethylene (PE) separator (the modified separator is denoted as AH-PE). The HNTs with hollow nanotubular structure construct a light skeleton and provide fast ion transport channels while Al2O3 particles function as heat-resistant fillers to inhibit the shrinkage of the separator at elevated temperatures. The total thickness of AH-PE separator is only 14 µm. Consequently, the mass increment of AH-PE separator decreases from 5 g/m2 to 3.5 g/m2, and the Gurley value reduces by 23%, compared with Al2O3 coated PE separator (A-PE). Due to the synergistic effects of Al2O3 and HNTs, AH-PE separator exhibits highly improved thermal stability (almost no shrinkage at 170 ℃ for 30 min), high Li+ transference number (up to 0.47), and long cycle life of 450 h for Li|Li cells. Moreover, the LiFePO4/Li cells assembled with AH-PE separators demonstrate improved rate capability and safety performance.
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