Search

Semi-hydrogenation of alkynes to alkenes using electrochemical approaches is an appealing alternative to conventional thermocatalytic strategies, as it efficiently utilizes water as the hydrogen source at ambient temperature. However, the precise modulation of atomic and electronic structures of catalytic Pd active sites remains a persistent challenge, particularly in enhancing the conversion yield of alkynes and improving the selectivity of alkenes. Here, we synthesize Pd nanoparticles anchored onto the surface of the defective two-dimensional Fe2O3 support, referred to as Pd/Fe2O3 catalysts, to conduct the electrocatalytic semi-hydrogenation of alkynes. Intriguingly, we observed the reconstruction of the atomic structure and configuration of Pd nanoparticles in the Pd/Fe2O3 catalysts due to metal–support interaction, caused by the hybridization of Pd d and O p orbitals. This interaction significantly weakens the binding strength of Pd sites in the Pd/Fe2O3 catalysts to the chemisorbed 4-aminophenylacetylene and reactive hydrogen intermediates. Consequently, Pd/Fe2O3 catalysts achieve a high conversion rate (99%) and selectivity (99%) in the semi-hydrogenation of 4-aminophenylacetylene coupled with high faradaic efficiency, outperforming both benchmark commercial Pd/C and other reference catalysts. Additionally, terminal alkynes featuring diverse functionalized groups, including those with easily reducible or passivated functionalities, can be efficiently semi-hydrogenated using Pd/Fe2O3 catalysts. [ABSTRACT FROM AUTHOR]

Selective catalytic oxidation of NH3 (NH3-SCO) is a promising method to reduce NH3 pollution. The Pt-based catalysts exhibited excellent activity in the NH3-SCO reaction under low temperatures. However, it was easy for the NH3 to be oxidized to N2O and NOx (NO and NO2) over the Pt-based catalyst, causing a low N2 selectivity. The CuSO4, which could supply both Brønsted and Lewis acid sites on the catalyst, was used to promote N2 selectivity. The N2 adsorption–desorption, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), inductively coupled plasma mass spectrometry (ICP-MS), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), NH3-temperature programmed desorption (NH3-TPD), H2-temperature programmed reduction (H2-TPR) and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were used to characterize the catalyst. The addition of CuSO4 could suppress the formation of N2O and NOx, thus the highest N2 selectivity on the catalyst increased from 21.2% to 78.1%. An imide mechanism was the main reaction mechanism on the Pt/TiO2 catalyst. After adding CuSO4, the NH3-SCO reaction over the CuSO4-Pt/TiO2 catalyst mainly followed an i-SCR mechanism where NH3 was oxidized to N2O and NOx, and then the newly formed N2O and NOx were reacted with NH3/NH4+ adsorbed on the Lewis and Brønsted acid sites via an NH3-SCR reaction over the catalyst, and finally N2 was formed. The acid sites performed an important role in the formation of N2 and this work should provide an effective method to promote N2 selectivity in a NH3-SCO reaction. [ABSTRACT FROM AUTHOR]

Photochromic materials coupled with photoswitchable luminescence functionalities are of particular interest due to their potential applications in switches and optical memory devices. However, the construction of such materials, especially those with two-color emission states, is still challenging. In this context, a rare Zn7 cluster-based host–guest MOF material, (bbmp)[Zn7(IPA)6(OH)4(H2O)2] (1) (H2IPA = isophthalic acid, bbmp·2I = 4,4′-([1,1′-biphenyl]-4,4′-diyl)bis(1-methylpyridin-1-ium) diiodide), was prepared by encapsulating an organic cation into an anionic MOF produced from zinc cations and isophthalic acid ligands, which exhibits reversible naked detectable photochromic properties varying from yellow to green upon UV-Vis light irradiation. The photoactive guest bbmp2+ and the short O⋯N+ distances between the oxygen atoms of the carboxylate groups and the pyridine ring play a crucial role in the photochromism of this compound. More interestingly, the luminescence color of this cluster-based host–guest material can be reversibly switched from green to blue upon irradiation, exhibiting photoswitchable luminescence properties. [ABSTRACT FROM AUTHOR]

In this work, a new kind of CdS–ZnO core–shell nanorods with controlled ZnO shell are first synthesized by a simple chemical deposition method in aqueous solution. The thickness and distribution of the ZnO shell can be accurately adjusted, and intimate contact interfaces between CdS and ZnO are well constructed. The optimal CSZ0.5 core–shell heterostructure exhibits a photocatalytic H2 evolution rate of 805.5 μmol h−1 without co-catalysts (3 mg of catalyst, equal to 268.5 mmol g−1 h−1), which is 12 and 895 times higher than that of CdS and ZnO, respectively, and is the maximum value among CdS-based photocatalysts under similar experimental conditions. The significant enhancement in the photocatalytic H2 evolution rate can be mainly attributed to three positive factors: the single-crystalline structure of CdS, the Z-scheme mechanism formed between CdS and ZnO, and the introduced ascorbic acid. The first two factors effectively promote the separation and migration of charge carriers, and the latter factor realizes efficient hydrogen spillover for CdS/ZnO to accelerate the photocatalytic hydrogen evolution reaction. In addition, the homogeneous ZnO shell grown on the CdS core efficiently suppresses the photo-corrosion of CdS, which endows CdS/ZnO with outstanding photostability. [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) is a robust water treatment technique due to its energy-efficient, low cost, and environmentally safe features. Recently, the utilization of faradaic electrode materials to construct hybrid capacitive deionization (HCDI) is considered to be one of the effective ways to address the drawbacks of the inferior desalination capacity of conventional CDI. Here, for the first time, a Na3MnTi(PO4)3/C (NTMP/C) composite was prepared via a sol–gel-calcination method and used as a faradaic electrode in HCDI. The NTMP nanoparticles were encapsulated in a carbon matrix, which could reduce the ion diffusion distance as well as ensure rapid ion transmission. In addition, taking the advantage of the high ratio of pseudo-capacitive performance and the two-species redox reaction of Ti4+/Ti3+ and Mn3+/Mn2+ couples, the obtained NTMP/C composite displayed a large ion removal capacity (72.2 mg g−1) (IRC), ultrafast ion removal rate (IRR) (21.6 mg g−1 min−1) and excellent cycle stability. Moreover, the mechanism of the Na+ removal of NTMP/C in the desalination process was investigated via electrochemical and ex situ structural characterization. This study indicates that NTMP/C can be an alternative faradaic electrode material towards CDI applications. [ABSTRACT FROM AUTHOR]

In this work, a novel strategy, one-step vulcanization of Cd(OH)Cl nanorods in the presence of ZnCl2 and Na2PdCl4, is successfully developed to synthesize CdS/ZnS/PdS nanotubes (NTs) for the first time. In this method, the three components (CdS, ZnS and PdS) are fully combined together at the nano-scale in the CdS/ZnS/PdS NTs, creating a large number of intimate contact interfaces. As a result, the optimized CdS/ZnS/PdS NTs exhibit a significantly enhanced photocatalytic H2 evolution rate of 1021.1 μmol h−1 (10 mg of catalyst), which is 11.4 and 16.3 times higher than that of pristine CdS NTs and ZnS nanoparticles (NPs), respectively, and is the maximum reported value for CdS-based photocatalysts under similar experimental conditions. Moreover, the apparent quantum efficiency of the optimal sample can reach 26.1% at 365 nm wavelength. The improved photocatalytic performance can be attributed to the synergistic effects of the hollow tubular structure, the CdS/ZnS heterostructure and the PdS co-catalyst. Due to the hollow tubular structure, both the inner and outer surfaces of CdS/ZnS/PdS NTs can act as reaction sites to rapidly consume electrons and holes, effectively suppressing their recombination. Both the CdS/ZnS heterostructure and PdS co-catalyst can efficiently promote the separation and transfer of charge carriers. This work may provide a new method for the design and construction of new photocatalysts with highly efficient H2 production. [ABSTRACT FROM AUTHOR]

A solvent-dependent oxidative dearomatization-induced divergent [5+2] cascade approach to bicyclo[3.2.1]octanes was described. This novel protocol enables a facile synthesis of a series of diversely functionalized ent-kaurene and cedrene-type skeletons in good yields and excellent diastereoselectivities. [ABSTRACT FROM AUTHOR]

Photochromic materials coupled with photoswitchable luminescence functionalities are of particular interest due to their potential applications in switches and optical memory devices. However, the construction of such materials, especially those with two-color emission states, is still challenging. In this context, a rare Zn 7 cluster-based host-guest MOF material, (bbmp)[Zn 7 (IPA) 6 (OH) 4 (H 2 O) 2 ] (1) (H 2 IPA = isophthalic acid, bbmp·2I = 4,4'-([1,1'-biphenyl]-4,4'-diyl)bis(1-methylpyridin-1-ium) diiodide), was prepared by encapsulating an organic cation into an anionic MOF produced from zinc cations and isophthalic acid ligands, which exhibits reversible naked detectable photochromic properties varying from yellow to green upon UV-Vis light irradiation. The photoactive guest bbmp 2+ and the short O⋯N + distances between the oxygen atoms of the carboxylate groups and the pyridine ring play a crucial role in the photochromism of this compound. More interestingly, the luminescence color of this cluster-based host-guest material can be reversibly switched from green to blue upon irradiation, exhibiting photoswitchable luminescence properties.