Science China Chemistry最新文献

Epoxy resins are widely valued for their ease of processing and versatile applications, yet they often face a critical trade-off between extended processing windows and rapid curing kinetics. While conventional latent curing systems have partially mitigated this issue, they still struggle with excessive brittleness. To overcome these limitations, we develop an imidazole-based latent curing agent that is synergistically blocked using dynamic covalent bonds and metal coordination. Specifically, one end of the imidazole is functionalized with a polyurethane oligomer, while the other is coordinated with copper ions. This design ensures an extended pot life while preserving ultra-low viscosity, which is suitable for the liquid molding process of composite structures. Upon thermal activation, both blocking agents rapidly dissociate, facilitating efficient curing. The resulting epoxy network incorporates metal coordination bonds, hydrogen bonding, and microphase separation, which work together to significantly enhance toughness that much higher than existing systems without compromising strength. We further demonstrate its potential for high-performance carbon fiber reinforced composites by successfully fabricating a full-scale automotive engine hood, highlighting the effectiveness and scalability of our material processing strategy.

Clusteroluminescence (CL) refers to the emergent luminescence observed in certain nonconjugated structures, particularly in polymer systems. In most cases, CL exhibits excitation-dependent emission, which is commonly explained by multiple intrachain and interchain through-space conjugation (TSC). However, in some systems, a permanent and excitation-independent emission is observed, which cannot be fully explained by the current TSC mechanism. In this work, through a systematic investigation of polyethylene glycol (PEG) with different molecular weights, we discovered the coexistence of two types of emission in high-molecular-weight PEG: (Type I) a distinct, excitation-independent emission with well-resolved fine structure at 395 nm, and (Type II) a broad, excitation-dependent long-wavelength emission. The Type II emission is generally attributed to through-space n-n conjugation within oxygen clusters. In contrast, combined theoretical and photophysical studies indicate that the origin of Type I emission is negative hyperconjugation between neighboring oxygen atoms and sp³ carbons. This work not only demonstrates the crucial role of negative hyperconjugation in CL but also clarifies the importance of polymerization in amplifying weak electronic interactions, thereby enabling emergent photophysical properties in polymers.

Electrochemical CO₂ reduction reaction (CO₂RR) is crucial for sustainable carbon cycling, while its efficiency is hindered by sluggish kinetics, competitive hydrogen evolution reaction (HER), and CO₂ mass transport limitation. Metal-organic frameworks (MOFs) feature tunable structures, high porosity, and diverse functionalities, making them highly valuable for the CO₂RR. They can not only serve as direct CO₂RR catalysts, producing C₁ or C₂₊ products via their metal nodes, organic linkers, or guest species, but also function as effective modulators of the reaction microenvironment. Notably, MOFs can improve the local CO₂ concentration through adsorption and molecular sieving, modulate surface hydrophobicity to stabilize the triple-phase boundary (TPB) and suppress HER, as well as precisely tune ion conduction to reduce the resistance and stabilize key reaction intermediates. This review summarizes recent advancements in MOF-based catalysts for CO₂RR, exploring their diverse active sites for C₁ and C₂₊ products formation, highlighting strategies for performance enhancement through microenvironment modulation, and proposing future research directions for employing MOFs to advance CO₂RR.

Neutral zinc-air batteries (ZABs) have emerged as a promising energy storage technology owing to their intrinsic safety, low cost, and environmental compatibility. However, several critical challenges, including sluggish oxygen electrocatalysis, interfacial pH instability, and limited reversibility of discharge products-continue to hinder their development. In this feature article, we summarize recent progress made by our group in establishing a multiscale regulation framework for neutral ZABs. This framework integrates electrolyte formulation, interfacial engineering, cathode architecture design, and hybrid battery strategies, all aimed at enhancing energy efficiency and cycling stability in neutral environments. Our findings provide new mechanistic insights into interfacial reaction control, electrolyte structure optimization, and discharge product regulation under near-neutral conditions. We also outline the remaining scientific challenges and discuss future directions toward the development of efficient and durable neutral ZABs through holistic electrolyte-electrode integration.

Organic nanotubes have garnered significant attention over recent decades due to their potential applications across various fields. Despite this, the synthesis of stable organic nanotubes with precise stereochemical control remains challenging. While dynamic covalent chemistry has proven to be a powerful tool for efficiently constructing stable organic nanotubes, precise stereochemical control of low-symmetry chiral nanotubes is still an area requiring further exploration. Here we report the synthesis of a low-symmetry chiral organic nanotube through dynamic covalent self-assembly of a rim-differentiated pentathiol-functionalized pillar[5]arene (p5-SH). Dimerization of this highly symmetric building block generates a covalently linked low-symmetry organic nanotube ([p5-S]₂). A pair of enantiomers, P′M-[p5-S]₂ and M′P-[p5-S]₂, was separated and characterized. The assembly and disassembly of [p5-S]₂ are redox-regulated, with disulfide bonds functioning as molecular switches. Furthermore, the synergistic effects of dual pillar[5]arene cavities in [p5-S]₂ create a deep cavity with a rigid asymmetric architecture. This structure significantly enhances the nanotube’s ability to recognize linear alkyl chains in solution, making it a promising candidate for various applications in materials science and nanotechnology.

Efficient extraction of uranyl [U(VI)O₂²⁺] from fluoride-containing wastewater is important for both uranium mining and fuel rod manufacturing. However, it remains challenging due to the strong interaction between U(VI)O₂²⁺ and F⁻, which results in the formation of water-soluble and stable [UO₂F_n]²⁻ⁿ (n = 0, 1, 2, 3, 4) complexes. Herein, we propose an innovative nanospace-confined adsorption electrocatalytic strategy (NAES) that enables efficient extraction of U(VI)O₂²⁺ from fluoride-containing wastewater. This is realized by rationally introducing amidoxime groups (R) into the interlayer region of a cobalt layered double hydroxide electrocatalyst (creating Co-LDH-R). The amidoxime groups selectively bind U(VI)O₂²⁺, which is further electrocatalytically converted to a K₅(UO₂)₂F₉ solid by the action of the Co²⁺ sites of Co-LDH-R through an electrocatalytic redox process in the presence of K⁺ and F⁻. Co-LDH-R can stably extract U(VI)O₂²⁺ from fluoride-containing wastewater streams, with a remarkable capacity of 7255.15 mg/g after 72 h, positioning it as one of the most effective U(VI) extractants reported to date. The generated solid K₅(UO₂)₂F₉ can be collected for storage or further processing. Therefore, our work offers a promising new pathway for uranium resource recovery under practical conditions.

Nitrate pollution and carbon emissions, driven by anthropogenic nitrogen cycle imbalance and fossil fuel overuse, pose serious threats to environmental and human health. Electrocatalytic C-N coupling of CO₂ with nitrogen-containing species offers a sustainable route for urea synthesis, contributing to nitrogen recycling and carbon neutrality. However, developing electro-catalysts with high activity, selectivity, and stability remains challenging. Recent advances in rationally designed copper (Cu)-based catalysts have deepened the understanding of C-N coupling mechanisms and structure-performance relationships. This review highlights recent progress in Cu-based electrocatalysts for urea synthesis (mainly for CO₂ and nitrate coupling), focusing on three key strategies: electronic structure modulation, defect engineering, and multi-site synergy. The reaction pathways are first summarized, followed by discussions on catalyst design principles aimed at optimizing intermediate adsorption, lowering C-N coupling barriers, and facilitating proton-coupled electron transfer. In-situ characterizations are employed to elucidate the mechanistic roles of these strategies. Finally, the key challenges and future directions for the application of Cu-based catalysts are outlined.

Achieving ultrahigh-affinity molecular recognition in aqueous media remains a key challenge in supramolecular chemistry. We report the synthesis of (+)-CA-C[4]B, a water-soluble chiral macrocycle derived from enantiopure BINOL, featuring eight carboxylate groups on its rims to enhance cavity depth and binding affinity. In aqueous media, (+)-CA-C[4]B exhibits ultrahigh 1:1 host-guest binding affinities up to 10¹³ M⁻¹ and 1:2 binding affinities up to 10¹⁶ M⁻². Notably, it supports dual-mode 1:2 binding: face-to-face for planar aromatic guests and head-to-head for spherical guests like adamantane. Combined with its high recognition affinities, superior fluorescence (quantum yield 43%) and circularly polarized luminescence (|g_lum| = 2.6 × 10⁻³), (+)-CA-C[4]B offers transformative potential for chiral supramolecular materials.