Latest ArticlesHydrogen peroxide (H2O2) synthesis generally involves the energy-intensive anthraquinone process. Alternatively, electrochemical synthesis provides a green, economical, and environmentally friendly route to prepare H2O2 via the two-electron oxygen reduction reaction, but this process requires efficient catalysts with high activity and selectivity simultaneously. Here, we report an N, O co-doped carbon xerogel-based electrocatalyst (NO-CX) prepared by a simple and economical method. The NO-CX catalyst exhibits a high H2O2 selectivity over 90% in a potential range of 0.2–0.6 V and a high H2O2 production rate of 1410 mmol gcat−1 h−1. The density functional theory calculations demonstrate that the coupling effect between N and O can effectively induce the redistribution of surface charge and the edge carbon atom adjacent to an ether group and a graphite nitrogen atom is the active site. This work provides a straightforward and low-cost process to produce highly selective H2O2 catalysts, which is in place for the expansion of electrocatalytic synthesis of useful chemicals.
Diabetic wounds lead to a decrease in quality of life and an increase in mortality. Current treatment strategies include preventing bacterial adhesion while improving microcirculation. As a new type of wound dressing that imitates natural skin, hydrogel has gradually emerged with its excellent properties. However, existing hydrogels rarely achieve satisfactory results in promoting wound repair and antibacterial simultaneously. In this case, we prepared methacrylic anhydride chemically modified hyaluronic acid as a hydrogel matrix, added polyhexamethylene biguanide as an antibacterial component, and loaded sodium alginate/salidroside composite microspheres which could sustainably release salidroside and thus promote angiogenesis. Hybrid hydrogel (HAMA/PHMB-Ms) was synthesized via photocrosslinking, and its chemical structure, particle size distribution and microstructure were characterized. The satisfactory antibacterial properties of the HAMA/PHMB(15%)-Ms hydrogel were studied in vitro, and its antibacterial rates against E. coli and S. aureus were 97.85% and 98.56%, respectively. In addition, after demonstrating its good biocompatibility, we verified that the HAMA/PHMB-Ms hydrogel has increased granulation tissue formation, more collagen deposition, more subcutaneous capillary formation, and better wound healing than blank control, HAMA and HAMA/PHMB hydrogel on the back wound model of diabetic mice. The results confirmed that HAMA/PHMB-Ms hydrogel was a promising material for the treatment of the diabetic wounds.
Homogeneous gold catalysis has demonstrated the preponderant capability of realizing a broad range of synthetically versatile alkyne functionalization over the last two decades. Though catalytic asymmetric alkyne transformation has focused on the principle of using gold catalysts either associated with chiral phosphine ligand or combined with chiral counterion, a variety of breakthroughs have been reported with the application of gold-complex and chiral organocatalyst cooperative catalysis strategy, which could enable the challenging transformations that cannot be realized by mono-catalysis with excellent stereoselectivity. This review will cover two general protocols in this field, including relay catalysis and synergistic catalysis, with emphasis on the detailed cooperative catalysts models to illustrate the roles of the two catalysts and highlight the potential synthetic opportunities offered by asymmetric cooperative catalysis.
A novel Mo-doped CuO catalyst is developed and used for low-temperature NH3-SCR reaction. Compared with the undoped CuO sample, the Mo doped CuO catalyst shows an increased SCR performance with above 80% NOx conversion at 175 ℃. The XRD and Raman results have confirmed the incorporation of Mo metal ions into CuO lattice to form Mo-O-Cu species which may be related to the enhanced SCR activity. The XPS and UV–vis results reveal the creation of electron interaction between Cu and Mo in this Mo-O-Cu system which provides an increased amount of Lewis and Brønsted acid sites, thereby promoting the adsorption capacity of NH3 and NOx as verified by NH3-TPD and NOx-TPD characterization. Besides, it also promotes the formation of oxygen vacancies, leading to the increasing of chemisorbed oxygen species, which improves the NO oxidation to NO2 activity. Furthermore, in situ DRIFTS technology was also used to study the reaction mechanism of this Mo doped CuO catalyst. The formed NO2 could react with NHx (x = 3, 2) species to enhance the low-temperature NH3-SCR activity via the "fast-SCR" reaction pathway. The nitrate and nitrite ad-species may react with NH3 and NH4+ ad-species through the L-H pathway.
Challenges of achieving efficient photodimerization of azaanthracene derivatives remain due to the low selectivity and slow reaction rate. In this paper, cucurbit[10]uril (CB[10]), with the largest rigid and hydrophobic cavity among CB[n]s, was used to affect the photodimerization reaction of four water-soluble 1-(2-)substituted azaanthracene derivatives (1-4). It revealed that 1-4 could form 1:2 host-guest complexes with CB[10] in aqueous solution. Irradiation of 1 in the presence of 0.5 equiv. of CB[10] selectively produced a head-to-tail (anti-HT) photodimer product. As for 2-4, CB[10] acted as a nanoreactor accelerating their photodimerization reaction in water. Our results suggest that photodimerization of azaanthracene derivatives could be promoted by the CB[10]-based host-guest strategy with high efficiency and selectivity.
A stimuli-responsive supramolecular polymer network has been constructed based on the host-guest interactions between the copolymer poly-P[5]A with pendent pillararene units and bis(sulfonium) diction guest G2. The formation mechanism of the supramolecular polymer network has been explored by the intensive study. With the addition of the competitive molecules and heating, the supramolecular polymer network could be dissociated and lead to clear changes in NMR spectroscopy and viscosity property.
Advanced oxidation processes (AOPs) are promising technology to remove organic pollutant in water. However, the main problem in the AOPs is the low generation of hydroxyl radical (•OH) owing to the low decomposition efficiency of hydrogen peroxide (H2O2). Herein, the spinel type cobalt acid manganese (MnCo2O4) with flower morphology was fabricated through a co-precipitation method. In situ Fourier transform infrared spectroscopy confirms that the MnCo2O4 with the optimal molar ratio of Co and Mn precursors (CM3, Co: Mn = 3) has more Lewis acid sites compared with single metal oxide catalysts (Co3O4 and Mn2O3), leading to the excellent performances for H2O2 decomposition rate constant on CM3, which is about 15.03 and 4.21 times higher than those of Co3O4 and Mn2O3, respectively. As a result, the obtained CM3 shows a higher ciprofloxacin degradation ratio than that of Co3O4 and Mn2O3. Furthermore, CM3 shows an excellent stability during several cycles. This work proposes effective catalysts for ciprofloxacin decomposition and provides feasible route for treating practical environmental problems.
Treatment of antibiotics contaminated water remains a global environmental challenge. In this study, tetracycline (TC) was found to effectively sensitize pure TiO2 for visible light photocatalytic degradation via a ligand-to-metal charge transfer mechanism. The sensitization was attributed to the formation of TC-TiO2 complex and the overlap of the molecular orbitals of TC and the conduction band of TiO2. The intermediate degradation products of TC, however, did not sensitize TiO2, which was the reason for the low mineralization rate. Nevertheless, our results showed that the intermediate degradation products of TC had significantly reduced bactericidal effects and less induction of antibiotic-resistance genes (ARGs). This study showcases an effective treatment of antibiotics-containing wastewater using the most common photocatalyst TiO2 with reduced risk in the spread of ARGs.
The increasing occurrence of pesticide micropollutants highlights the need for innovative water treatment technologies, particularly for small-community and household applications. Electro-oxidation is being widely studied in this area, unfortunately, safe, stable and efficient electrocatalytic anodes without released heavy metal ions are still highly required. In this study, we fabricated a Pt/Ti anode by high energy pulse magnetron sputtering (HiPIMS-PtTi) which was used to decompose dichlorvos (DDVP) and azoxystrobin (AZX) in water. The results show that the reaction rate constant (kENR) on HIPIMS was 35.7 min–1 (DDVP) and 41.3 min–1 (AZX), respectively, superior to electroplating Pt/Ti anode (EP-PtTi). The identification of radicals (•OH, 1O2, •O2−) and micro-area analyses evidenced that Pt atoms were embedded into the TiO2 lattice on the surface of Ti plate by high-energy ions, which resulted in more adsorbed hydroxyls, and higher production of •OH under polarization conditions. Besides, the electro-oxidation intermediates of DDVP and AZX were identified and the degradation pathways were speculated: (1) indirect oxidation dominated by •OH attack, and (2) direct electron transfer reaction of pesticides on the anode surface. The cooperated reactions achieve the complete degradation and highly efficient mineralization of DDVP and AZX.
Ni(0)-catalyzed regio- and diastereodivergent [4 + 2] annulation of biphenylenes with α, β unsaturated ketones is described. This solvent-controlled diastereodivergent reaction integrates C-C bond cleavage of biphenylene and C=C double bond insertion selectivity, offering a mild approach to all possible diastereoisomers of 9, 10-dihydrophenanthrene derivatives from the same starting materials.
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