Monthly Archives: September 2023

Highly Durable PtNi Alloy on Sb‐Doped SnO2 for Oxygen Reduction Reaction with Strong Metal‐Support Interaction

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Highly Durable PtNi Alloy on Sb-Doped SnO2 for Oxygen Reduction Reaction with Strong Metal-Support Interaction

PtNi/Sb0.11SnO2 with high durability was synthesized by adjusting the doping amount of antimony. The prepared PtNi/Sb0.11SnO2 retained excellent catalytic activity and hardly reduced half-wave potential in acidic conditions after 10,000 cycles, which displayed its high durability.


Abstract

Carbon-supported Pt is currently used as catalyst for oxygen reduction reaction (ORR) in fuel cells but is handicapped by carbon corrosion at high potential. Herein, a stable PtNi/SnO2 interface structure has been designed and achieved by a two-step solvothermal method. The robust and conductive Sb-doped SnO2 supports provide sufficient surfaces to confine PtNi alloy. Moreover, PtNi/Sb0.11SnO2 presents a more strongly coupled Pt-SnO2 interface with lattice overlap of Pt (111) and SnO2 (110), together with enhanced electron transfer from SnO2 to Pt. Therefore, PtNi/Sb0.11SnO2 exhibits a high catalytic activity for ORR with a half-wave potential of 0.860 V versus reversible hydrogen electrode (RHE) and a mass activity of 166.2 mA mgPt −1@0.9 V in 0.1 M HClO4 electrolyte. Importantly, accelerated degradation testing (ADT) further identify the inhibition of support corrosion and agglomeration of Pt-based active nanoparticles in PtNi/Sb0.11SnO2. This work highlights the significant importance of modulating metal-support interactions for improving the catalytic activity and durability of electrocatalysts.

Exploring the Divergent Reactivity of Vinyl Radicals Emanating from Alkynes and Thiols via Photoredox Catalysis

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Exploring the Divergent Reactivity of Vinyl Radicals Emanating from Alkynes and Thiols via Photoredox Catalysis

This review describes the behaviour of vinyl radicals produced through photoredox catalysis and how different reactivity patterns have been achieved by manipulating its chemistry. The focus has been on constructing various valuable scaffolds through 1,1-difunctionalization, 1,2-difunctionalization, and cyclization reactions.


Abstract

Organic chemistry has seen a surge in visible-light-driven transformations, which offer unique reaction pathways and access to new synthetic possibilities. We aim to provide a comprehensive understanding of state-of-the-art photo-mediated alkyne functionalization, with a focus on the reactive behavior of vinyl radicals. This review outlines our contributions to the field, including developing new methods for forming carbon-carbon and carbon-heteroatom bonds.

Improvements in the Electrochemical Performance of Sodium Manganese Oxides by Ti Doping for Aqueous Mg‐Ion Batteries

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Improvements in the Electrochemical Performance of Sodium Manganese Oxides by Ti Doping for Aqueous Mg-Ion Batteries

Sodium manganese oxides as positive electrode materials for aqueous magnesium-ion batteries have attracted extensive attention. However, the structural stability of sodium manganese oxides is poor, thus we proposed a production process of titanium-doped sodium manganese oxides and used it as positive electrode materials for aqueous magnesium-ion batteries to obtain good electrochemical performance.


Abstract

In recent times, the research on cathode materials for aqueous rechargeable magnesium ion battery has gained significant attention. The focus is on enhancing high-rate performance and cycle stability, which has become the primary research goal. Manganese oxide and its derived Na−Mn−O system have been considered as one of the most promising electrode materials due to its low cost, non-toxicity and stable spatial structure. This work uses hydrothermal method to prepare titanium gradient doped nano sodium manganese oxides, and uses freeze-drying technology to prepare magnesium ion battery cathode materials with high tap density. At the initial current density of 50 mA g−1, the NMTO-5 material exhibits a high reversible capacity of 231.0 mAh g−1, even at a current density of 1000 mA g−1, there is still 122.1 mAh g−1. It is worth noting that after 180 cycles of charging and discharging at a gradually increasing current density such as 50–1000 mA g−1, it can still return to the original level after returning to 50 mA g−1. Excellent electrochemical performance and capacity stability show that NMTO-5 material is a promising electrode material.

The Growing Field of Photoswitchable Macrocycles: A Promising Way to Tune Various Properties with Light

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The Growing Field of Photoswitchable Macrocycles: A Promising Way to Tune Various Properties with Light

Photoswitchable macrocycles: Recent development of azobenzene, diarylethene, (Stiff-)stilbene or dihydroazulene-based photoswitchable macrocycles, for which conformation, dynamic, photo or thermal isomerization can be controlled by multiple photoswitching units, coordination-driven self-assembly, anion/cation binding or pH modulation, is reviewed, along with applications in encapsulation and release, in the reversible modulation of chemical, biological, electronic, fluorescent and chiroptical properties by light.


Abstract

Thanks to supramolecular interactions of macrocyclic compounds with their guest ions or molecules, macrocycles have found wide applications in molecular and chiral recognition, separation, transportation, molecular machines, and so on. Photoswitchable macrocycles are especially appealing and attracting more and more interest because the embedded molecular photoswitch enables dynamic control of molecular shape, conformation, and different properties by light, a non-invasive, remote and highly tunable stimulus. With available photochromic compounds, various photoswitchable macrocycles have been developed. In this review paper, we describe the recently reported photoswitchable macrocyclic compounds, with a focus on the control of the macrocyclic structure, dynamic, photo or thermal isomerization, as well as their applications on encapsulation and release of ionic or aromatic species, on the reversible modulation of chemical, biological, electronic, fluorescent and chiroptical properties by light.

Chiral and Luminescent Organic Radicals

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Chiral and Luminescent Organic Radicals

Chiral luminescent radicals: Based on the origin of chirality, we classified the currently reported chiral luminescence radicals into three categories, intrinsic chiral luminescent radicals, luminescent radicals with chiral substitutions, and field-regulation-induced chiral luminescent radicals. This brief review of their properties aims to provide basic guidelines for the development of these systems and to support further development of novel chiral luminescent radical systems.


Abstract

Chiral luminescent materials are a class of materials capable of emitting circularly polarized light (CPL). Radicals are unique open-shell compounds with exceptional photoelectromagnetic properties that can be exploited in constructing novel chiral luminescent materials. This Concept discussed three main catalogues for producing organic CPL radicals, intrinsic chiral luminescent radicals, luminescent radicals with chiral substitutions, and field-regulation-induced chiral luminescent radicals. The brief review of their properties aims at providing basic guidelines and supporting further development of novel chiral luminescent radical systems.

Structural design of π‐d conjugated TMxB3N3S6 (x = 2, 3) monolayer toward electrocatalytic ammonia synthesis

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Single−atom catalysts (SACs) have attracted wide attentions to be acted as potential electrocatalysts for nitrogen reduction reaction (NRR). However, the coordination environment of the single transition metal (TM) atoms is essential to the catalytic activity for NRR. Herein, we proposed four types of 3-, 4-coordinated and π−d conjugated TMxB3N3S6 (x = 2, 3, TM = Ti, V, Cr, Mn, Fe, Zr, Nb, Mo, Tc, Ru, Hf, Ta, W, Re and Os) monolayers for SACs. Based on density functional theory (DFT) calculations, I-TM2B3N3S6 and III-TM3B3N3S6 are the reasonable 3-coordinated and 4-coordinated structures screening by structure stable optimizations, respectively. Next, the structural configurations, electronic properties and catalytic performances of 30 kinds of the 3-coordinated I-TM2B3N3S6 and 4-coordinated III-TM3B3N3S6 monolayers with different single transition metal atoms were systematically investigated. The results reveal that B3N3S6 ligand is an ideal support for TM atoms due to existence of strong TM−S bonds. The 3-coordinated I-V2B3N3S6 is the best SAC with the low limiting potential (UL) of −0.01 V, excellent stability (Ef = −0.32 eV, Udiss = 0.02 V) and remarkable selectivity characteristics. This work not only provides novel π−d conjugated SACs, but also gives theoretical insights into their catalytic activities and offers reference for experimental synthesis.

Ligating Catalytically Active Peptides onto Microporous Polymers: A General Route Toward Specifically‐Functional High‐Surface Area Platforms

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A versatile post-synthetic modification strategy to functionalize a high surface area microporous network (MPN-OH) by bioorthogonal inverse electron-demand Diels-Alder (IEDDA) ligation is presented. While the polymer matrix is modified with a readily accessible norbornene isocyanate (Nb-NCO), a set of functional entities, presenting the robust asymmetric 1,2,4,5-tetrazine (Tz) allows easy functionalization of the MPN by chemoselective Nb/Tz ligation. A generic route is demonstrated, modulating the internal interfaces by introducing carboxylates, amides or amino acids as well as an oligopeptide d-Pro-Pro-Glu organocatalyst. The MPN-Peptide construct largely retains the catalytic activity and selectivity in an enantioselective enamine catalysis, proving remarkable availability in different solvents, offers heterogeneous organocatalysis in bulk and shows stability in recycling settings.

Why The Perfectly Symmetric Cobalt‐Pentapyridyl Loses the H2 Production Challenge: Theoretical Insight into Reaction Mechanism and Reduction Free Energies

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Researchers have extensively investigated photo-catalytic water reduction utilizing Cobalt-based catalysts with poly-pyridyl ligands. While catalysts exhibiting distorted poly-pyridyl ligand demonstrate higher H2 production yields, those with ideal octahedral coordination display poor performance. This outcome suggests the crucial role of ligand framework in catalytic activity, yet reasons behind the disparity in H2 production rates for catalysts with octahedral geometries remain unclear. We theoretically examined the water reduction mechanism of Co-based poly-pyridyl catalyst, CoPy5, having perfect octahedral coordination. We clarified the effect of octahedral coordination by utilizing each intermediate step of ECEC mechanism. We determined spin states, solvent response, electronic structures, and reduction free energies. CoPy5 with perfect octahedral coordination, alongside its distorted counterparts, exhibit similar spin states as the reaction progresses through each intermediate step. However, the first reduction free energy obtained for the CoPy5 is slightly higher than that of its distorted counterparts. Following the second protonation, resulting H2 molecule experiences limited diffusion from the Co center due to the compact structure of the CoPy5, which blocks the Co center for the next H2 production cycle. Catalysts having distorted octahedral geometries facilitate fast removal of H2 into the solvent. Thus, the reaction center becomes immediately available for subsequent H2 production.

Chain‐walking polymerization of ethylene and 1‐octene with ortho‐phenyl‐based α‐diimine Ni (II) catalysts

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Chain-walking polymerization of ethylene and 1-octene with ortho-phenyl-based α-diimine Ni (II) catalysts

The ortho-phenyl-substituted Ni catalysis system based on α-diimine with variable electronic nature are highly active toward ethylene polymerization to synthesize high molecular weight polyethylene, and conducted the chain-walking polymerization of 1-octene to produce highly branched polyolefins.


A class of ortho-phenyl-substituted Ni (II) α-diimine complexes with variable electronic nature in the 4-phenyl position, {[(4-Me-2-(4-R-C6H4)C6H3N=C)2Naphth]NiBr2, R = OMe (C1); R = Me (C2); R = H (C3)}, was prepared and characterized. These nickel dibromide complexes were confirmed by X-ray crystallography analysis and crystallized as a centrosymmetric bromine-bridged dimer in a distorted tetrahedral geometry at the two Ni (II) centers connected by a four-membered ring. Because of the conjugation effect and steric hindrance effect of ortho-phenyl substituent, these Ni-Et2AlCl systems via controlled chain-walking ethylene polymerization performed with high catalytic activities of up to 3.10 × 106 g PE (mol Ni h)−1 to yield high molecular weight branched PEs with narrow M w/M n values (PDI ≤ 2.39). This Ni (II) system also conducted the chain-walking polymerization of 1-octene, resulting in highly branched polyolefins (up to 107 branches/1000C).

Novel core–shell magnetic nanoparticles@Zeolitic imidazolate with glycerol‐nickel for the synthesis of dihydropyrimidinones

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Novel core–shell magnetic nanoparticles@Zeolitic imidazolate with glycerol-nickel for the synthesis of dihydropyrimidinones

A novel Fe3O4-ZIF-8@Glycerol-Ni nanocatalyst was synthesized. Highly efficient catalytic activity was acquired for synthesizing dihydropyrimidinones with ethanol as suitable solvent in the reaction.


The present study reported a novel and eco-friendly synthesis of Fe3O4@ZIF-8@Glycerol-Ni nanocatalyst via a multistep process. The as-prepared catalyst was used due to its high efficiency, low cost, and biocompatibility for the fabrication of dihydropyrimidinones by Biginelli multicomponent reactions of aryl aldehyde, ethyl acetoacetate, and urea under ambient status. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Brunauer-Emmet-Teller (BET), vibrating sample magnetometry (VSM), scanning electron microscopy and energy dispersive X-ray (SEM-EDS), inductively coupled plasma (ICP), elemental mapping analysis (EMA), thermogravimetric analysis (TGA), Raman, and transmission electron microscopy (TEM) techniques were successfully utilized to evaluate the nanocatalyst. The advent of the peaks confirmed the presence of nickel on the catalyst's surface due to the oxygen and nickel, and the nanoparticle size is 10–15 nm. Eventually, nano-heterogeneous catalyst exhibits high performance as well as good selectivity in the synthesis of dihydropyrimidinones. Also, it can be recycled up to multiple fresh runs with no significant loss of catalytic efficiency.