ChemCatChem最新文献

Chitosan, a renewable marine polysaccharide derived from chitin, holds significant potential for conversion into high-value chitooligosaccharides with superior bioactivity and water solubility. However, the intrinsically poor solubility and low bioavailability of native chitosan severely limit its efficient utilization, necessitating the development of effective depolymerization strategies. This review comprehensively examines enzymatic depolymerization as a sustainable and efficient alternative to conventional chemical and physical methods, offering superior specificity, mild reaction conditions, and environmental compatibility. We begin with a critical comparison of these strategies to underscore the need for the development of biocatalytic approaches. Subsequently, we explore the diversity of chitosan-degrading enzymes across various glycosyl hydrolase families, detailing their catalytic mechanisms, cleavage specificities, and key structural domains governing substrate recognition and hydrolysis. The review further summarizes protein engineering strategies, including directed evolution, semi-rational design, and rational design, used to enhance chitosanase activity, thermostability, and product specificity. Finally, we discuss persistent challenges, such as the lack of crystal structures for certain enzyme families and the complexity of enzyme-substrate interactions. Future research will focus on resolving uncharacterized chitosanase structures, deepening mechanistic understanding of enzyme-substrate interactions, and integrating artificial intelligence with synthetic biology to develop robust biocatalysts tailored for industrial applications.

A series of Cu^I–acetylide complexes with a cheap and robust phenanthroline ligand, that is, (phen)CuCCR (R = H, Ph), were found to have a promising catalytic activity toward alkynylation of formaldehyde. Phenylacetylene and acetylene were selectively converted into the corresponding mono-propargylic alcohols with moderate to high yields without addition of base, while traditional heterogeneous catalysts yield 1,4-butynediol (BYD) almost quantitatively. The Cu^I complex was recovered via a biphasic system, allowing easier extraction of the reaction products with water. Two possible reaction pathways via mononuclear and dinuclear active complexes are proposed, where the former is likely more relevant.

Electrochemical CO₂ reduction to multicarbon C₂₊ products requires efficient C─C coupling while maintaining catalytically favorable Cu states under strongly reducing conditions. Herein, Ga-modified core–shell Cu₂O catalysts are constructed by a wet-chemical reduction method to couple Cu-valence regulation with oxygen-defect generation within a phase-preserved Cu₂O framework. Ga incorporation retains the ca. 200 nm core–shell morphology but perturbs the local Cu─O environment, increases the Cu⁺/Cu⁰ ratio from 2.54 to 3.45, and raises the defect-associated O 1s contribution from 75.13% to 82.94%. In a flow cell containing 1.0 M KOH, the optimized Ga/Cu₂O-II catalyst delivers a C₂₊ Faradaic efficiency of 73.5%, a C₂₊ partial current density of 251 mA cm⁻², and an FE_C2+/FE_C1 ratio of 6.8 at −1.26 V versus RHE; the ethanol Faradaic efficiency reaches 37.9%. After 12 h electrolysis, the Cu⁺/Cu⁰ ratio remains 2.94 and FE_C2+ remains above 60%. The combined structural, electrochemical, and post-reaction results support a dual-regulation picture in which a Cu⁺-rich Cu⁺/Cu⁰ surface favors carbon-intermediate retention and C─C coupling, while oxygen-deficient sites increase the population of accessible adsorption environments and facilitate conversion of oxygen-containing intermediates. This work demonstrates a simple strategy for stabilizing a catalytically productive mixed-valence/defect state of Cu₂O for high-rate C₂₊ electrosynthesis.

Developing high-performance and magnetically recoverable photocatalysts through rational structural engineering is an effective strategy for improving the photocatalytic degradation of antibiotic pollutants. In this work, a Bimodified ZnFe₂O₄/biochar composite (BBZ) was successfully synthesized via a facile hydrothermal method by combining magnetic ZnFe₂O₄ nanoparticles with biomassderived biochar. The optimized 0.09BBZ delivered the best adsorptionphotocatalytic performance for tetracycline (TC), with 87.3% removal within 180 min under visible light, 74.9% and 10.1% higher than pristine biochar and ZnFe₂O₄/biochar (BZ), respectively. Characterizations confirmed Bidoping and biochar synergistically improved physicochemical properties via widened visible-light absorption, narrowed bandgap, accelerated interfacial charge transfer and inhibited electronhole recombination, boosting photocatalytic activity. Moreover, BBZ possessed favorable magnetic recyclability and stability, retaining 75% TC removal after five cycles. This work demonstrates that the combined strategy of elemental modification and biochar coupling provides an effective route for regulating the electronic structure and photocatalytic properties of ZnFe₂O₄-based materials, offering a promising photocatalyst for the efficient removal of antibiotic contaminants from water.

Selective oxidation of aliphatic alcohols is a pivotal yet challenging C─H activation reaction. While non-adiabatic concerted proton-electron transfer (CPET) theoretically accelerates kinetics, efficient base-free heterogeneous catalysts remain elusive. Herein, we report Pt-Ca²⁺/dendritic mesoporous silica nanosphere (DMSN) catalysts prepared via sequential Ca²⁺ impregnation and Pt immobilization. The optimized catalyst exhibited exceptional performance in the aqueous-phase oxidation of isononyl alcohol (3,5,5-trimethylhexanol), achieving 95.1% conversion and 99.7% selectivity (120°C, 24 h) toward isononanoic acid. Surface hydrophobization effectively suppressed Ca²⁺ leaching, enabling high activity retention over four catalytic cycles. Mechanistic investigations reveal that Ca²⁺ plays a dual role: providing alkaline sites for alcoholic hydroxyl group deprotonation while templating a structural water network within confined channels to facilitate non-adiabatic CPET during C─H activation—a function mirroring the pivotal role of Ca²⁺ within the Mn₄CaO₅ cluster of Photosystem II in facilitating water splitting.

Global ammonia production is dominated by the energy-intensive Haber-Bosch process, motivating the development of sustainable electrochemical alternatives. While lithium- and calcium-mediated systems in organic solvents have relatively high yields, aqueous electrochemical nitrogen reduction (N₂ER) remains inefficient. Density functional theory (DFT) studies have significantly advanced the understanding of N₂ER in aqueous solution; however, most have focused on thermodynamic and/or kinetic analyses to elucidate reaction mechanisms, while orbital-level insights remain largely unexplored. Here, we combine DFT calculations with intrinsic bond orbital analysis to examine orbital evolution during 13 protonation steps of N₂ER. This approach identifies the orbitals responsible for proton accommodation in each intermediate. We find that nine of the 13 steps involve nitrogen lone-pair orbitals. These results suggest that protonation kinetics in aqueous N₂ER are strongly influenced by interactions between nitrogen lone pairs and the local solvation environment, including cations and hydrogen bonding. Moreover, surface modifications, which profoundly affect the reactivity of the metal–nitrogen σ bond but have a lesser influence on nitrogen lone-pair orbitals are not expected to have a direct impact on the protonation kinetics of N₂ER. Thus, rational manipulation of the local electrochemical environment, rather than solely modifying the catalyst surface, may be essential for improving N₂ER performance.