Science China Chemistry最新文献

Circularly polarized organic light-emitting diode (CP-OLED) has attracted increasing interest for its efficient ability to generate circularly polarized light directly. So far, many CP-OLEDs were successfully fabricated with chiral emitters or chiral hosts. In this study, a new strategy based on chiral electron transporting layer is proposed to construct CP-OLEDs. A pair of chiral electron transporting materials, 1,3,5-tris((R/S)-4-isopropyl-4,5-dihydrooxazol-2-yl)benzene ((R/S)-TOxⁱPr), are firstly designed and synthesized. The crystalline films of (R/S)-TOxⁱPr show circularly polarized photoluminescence with photoluminescence dissymmetry factors of −0.067 and +0.041, respectively. The CP-OLEDs based on (R/S)-TOxⁱPr and three types of achiral emitters all exhibit circularly polarized electroluminescence, showing feasibility and strong versatility of this new strategy. The mechanism is attributed to in-situ electrical excitation instead of simply light filtering of non-circularly polarized light. This work demonstrates a new approach for realizing circularly polarized electroluminescence which may provide a valuable strategy to develop CP-OLEDs.

The emergence of solid-state batteries (SSBs) has generated significant interest in the field of energy storage, primarily due to their advantages such as high safety, high energy density and long lifetime. Solid state electrolytes (SSEs) play a crucial role in SSBs, which not only affects the ion transport efficiency, but also relates to the overall performance and stability of the batteries. In recent years, SSEs based on covalent organic frameworks (COFs) have become a research focus in the battery field because of their unique structural characteristics and excellent performance. This review aims to provide an overview of the application and latest progress of COF-based SSEs in the field of advanced batteries. Firstly, the structural features of COFs and their advantages as SSEs are briefly introduced, followed by a summary of the types of COF-based SSEs (including neutral COF-based SSEs and ionic COF-based SSEs). The latest research progress in lithium ion batteries (LIBs), lithium metal batteries (LMBs), proton exchange membrane fuel cells (PEMFCs) and other advanced batteries recently is also discussed. Finally, we summarize and outlook the current research status, the challenges faced in practical application, the future research directions and application prospects of COF-based SSEs.

A regioselective C-C bond cleavage/aminocarbonylation cascade is presented. In recent years, tremendous progress has been made in the alkoxyl radical-mediated C-C bond cleavage of unstrained monocarbocycles. In contrast, the deconstruction and functionalization of bicyclic skeletons has been less developed and has mainly focused on the ring expansion process. Inspired by the aromatization-driven C-C bond cleavage, here we demonstrate a ring-opening/aminocarbonylation cascade under copper catalysis, in which the formation of a stable γ-lactam or succinimide skeleton reverses the selectivity of C-C cleavage. Remarkably, the photo and thermal assistance is not required when the succinimide skeleton is formed during the ring opening process. DFT calculations revealed that this unexpected ring-opening process is thermodynamically and kinetically favourable.

Radical-involved allylation reactions have emerged as a powerful platform for construction of carbon-carbon and carbonheteroatom bonds, facilitating the strategic incorporation of diverse allyl moieties. Nevertheless, this burgeoning field still faces ongoing challenges, including limitations of radical precursors and coupling partners, and difficulties in achieving enantiocontrol. Herein, we report for the first time a highly enantioselective radical allylation involving β-keto esters with vinyl cyclopropanes utilizing a synergistic dual photoredox/nickel catalysis under visible light irradiation. The mild and redox-neutral catalytic protocol demonstrates an extensive substrate compatibility and good functional tolerance, providing access to enantioenriched β-keto esters featuring quaternary α-stereocenter with good yields and high enantioselectivities. Preliminary mechanistic studies have uncovered that the success of the reaction hinges on the dual roles of nickel catalyst, including in situ formation of photoredox sensitive substrate/Ni complex and the ensuing asymmetric radical addition step.

Synthesis of value-added chemicals from biomass is an essential strategy to mitigate the global dependency on fossil resources and achieve the aim of carbon neutrality. Thereinto, ethanol and acetic acid are crucial biomass-derived platform molecules. Recently, catalytic upgrading ethanol and acetic acid into C4 energy-intensive fuels and chemicals via the elongation of carbon backbone has received widespread attention. The primary focus of this review is to systematically describe the recent breakthrough in the conversion of ethanol or acetic acid to C4 chemicals including 1,3-butadiene, n-butenes, isobutene or n-butanol. Special attentions will be given to heterogeneous catalyst design strategies, reaction parameters on the catalytic performance along with the relevant mechanism investigations, as well as their future challenges and opportunities. The present review will provide the detailed insights into the synthesis of C4 chemicals from biomass-derived ethanol and acetic acid and shed a light on the development of highly efficient catalysts.

Plastics have become omnipresent in modern life due to their versatility and durability. However, this convenience comes at the cost of substantial waste generation. The inherent chemical stability of plastics complicates its recycling, leading to environmental pollution and ecological threats. This mini-review highlights recent advancements in addressing this challenge by oxidative transformation of polyethylene (PE) into new functional polymers, value-added chemicals, and carbon-based materials. We first discuss the introduction of hydroxyl, carbonyl groups onto PE with a focus on the functionalization degree and selectivity. Subsequently, approaches for PE oxidation into dicarboxylic acids and short-chain oxidized PE are described and compared, with an emphasis on the tandem reactions for converting mixed dicarboxylic acids into other value-added chemicals. We also briefly discuss the oxidative transformation of PE into carbon-based materials and summarize the progress in qualitative and quantitative analysis of oxidation products. Finally, we conclude this mini-review by highlighting the challenges and opportunities in the field.

Structure determination plays the most crucial role in the discovery of novel functional materials, because only by knowing the intrinsic structures can we accurately and completely understand their properties and applications. However, most new materials are obtained in polycrystalline form or even as mixtures with multiple phases when first synthesized, presenting significant challenges in their structure determination and phase elucidation. Fortunately, the developed three-dimensional electron diffraction (3DED/MicroED) has provided a promising solution to overcome these challenges. In this study, we have constructed a state-of-the-art 3DED/MicroED data acquisition equipment by integrating a hybrid-pixel detector with a script developed for SerialEM, and thus successfully developed an automated 3DED/MicroED method for the high-throughput structure determination. To demonstrate its effectiveness, a multiphase sample with complex porous structures is employed, showcasing that individual phases and their structures can be identified and determined, respectively. One remarkable finding is the identification of an impurity metal-organic framework (MOF) that is completely invisible to traditional powder X-ray diffraction in a supposedly “pure” commercial MOF sample. Additionally, our method also enables the atomic-resolution structure determination of flexible covalent organic framework materials, which are highly sensitive to electron beams. Moreover, a new microporous aluminoborate is discovered using this rapid structure determination method. These experimental results highlight the enormous potential of our 3DED/MicroED method in the field of new materials discovery, offering a powerful tool for the structure determination of polycrystalline functional materials.

Styrene-butadiene rubber (SBR) is an indispensable material in modern society, and the necessity for enhanced mechanical properties in SBR persists, particularly to withstand the rigors of challenging environmental conditions. To surmount the limitations of conventional cross-linking modes, mechanical bonds stabilized by host-guest recognition are incorporated as the cross-linking points of SBR to form mechanically interlocked networks (MINs). Compared with covalently cross-linked network, the representative MIN exhibits superior mechanical performance in terms of elongation (1392%) and breaking strength (4.6 MPa), whose toughness has surged by 17 times. Dissociation of host-guest recognition and subsequent sliding motion provide an effective energy dissipation mechanism, and the release of hidden length is also beneficial to enhance toughness. Furthermore, the introduction of the rotaxane cross-links made the network more pliable and possess damping and elastic properties, which can return to initial state with one minute rest interval. We aspire that this direct introduction method can serve as a blueprint, offering valuable insights for the enhancement of mechanical properties in conventional commercial polymer materials.

Ethylene oxide (EO) and ethylene glycol (EG) are two important commodity chemicals and are industrially produced from petroleum-derived ethylene via thermocatalytic processes. The overoxidation of ethylene and the implementation of high temperature and pressure lead to substantial CO₂ emission. Renewable energy-driven electrocatalysis provides a low-carbon route for upgrading ethylene under mild conditions, especially when it couples with ethylene electrosynthesis from CO₂. In this minireview, we summarize recent achievements in the selective electrocatalytic oxidation of ethylene to EO and EG. Three main reaction routes including direct electrocatalytic oxidation with water, indirect electrocatalytic oxidation with halide mediators, and tandem electrocatalytic and thermocatalytic oxidation with hydrogen peroxide intermediate, are discussed. Some representative catalyst systems and reactor designs are exemplified. We discuss the existing scientific and technical challenges of electrocatalytic ethylene upgrading in terms of reaction rate, selectivity, and long-term stability, and propose future research directions and opportunities for pushing the process towards practical application.

CO₂ hydrogenation to higher alcohols (C₂₊OH) is an effective way to realize carbon recycling, which can not only reduce the CO₂ amounts in atmosphere and mitigate the greenhouse effect, but also provides a new route to synthesize important chemicals. However, this process is a challenge because the inert CO₂ molecule is difficult to be activated and undergo C–C coupling. The key to achieve selective conversion of CO₂ to C₂₊OH is to design high-performance catalytic systems and unravel the reaction mechanism. In this review, we report several typical CO₂ hydrogenation-to-C₂₊OH catalyst materials, including noble-metal catalysts, Cu-based catalysts, Co-based catalysts and Mo-based catalysts, and evaluate the effects of various promoters on the catalytic performance and reaction mechanism. It will provide not only fundamental insights into the CO₂ hydrogenation-to-C₂₊OH reaction mechanism, but also guidance for the development of related high-performance catalysts.