Journal of the American Chemical Society
·
2020
·
IF 14.612
Hai-Fang Li,Wenbo Cao,Xiaoxiao Ma,Xiaobo Xie,Yu Xia,Zheng Ouyang
The [2 + 2] photocycloaddition of alkenes and carbonyls is of fundamental interest and practical importance, as this process is extensively involved in oxetane-ring constructions. Although individual carbonyl group or alkene moiety has been utilized as photoactive species for oxetane formations upon ultraviolet photoexcitation, direct excitation of the entire noncovalent complex involving alkene and carbonyl substrates to achieve [2 + 2] photocycloadditions is rarely addressed. Herein, complexes with noncovalent interactions between benzophenone and C═C bonds in unsaturated lipids have been successfully characterized, and for the first time a [2 + 2] cycloaddition leading to the formation of oxetanes has been identified under visible-light irradiation. The mechanism of this reaction is distinctly different from the well-studied Paternò–Büchi reaction. The entire complexes characterized as dimeric proton-bonded alkene and carbonyl substrates can be excited under visible light, leading to electron transfer from the alkene moiety in fatty acyls to the carbonyl group within the complex. These results provide new insight into utilizing noncovalent complexes for the synthesis of oxetanes in which the excitation wavelength becomes independent of each individual substrate.
研究领域:
有机化学
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光化学
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材料科学
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LANGMUIR
·
2026
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IF 4.4
Honglin Li,Yingqi Duan,Qingwen Feng,Linjiao Wei,Jingbin Zeng,Ziyue Chen,Qingtong Zhang,Yanpeng Chen,Zifeng Yan
Ag–Cu tandem catalysis provides an effective strategy to enhance C2+ selectivity in the electrochemical CO2 reduction reaction (CO2RR) by integrating CO generation and utilization for C–C coupling. Here, we report a series of Ag@Cu2O, Ag@CuO, and Ag@CuO-BDC core–shell catalysts designed to regulate the CO generation, Cu-oxidation states, and surface structures. The Ag@Cu2O catalysts exhibit pronounced tandem effects, suppressing CH4 formation while enhancing the C–C coupling on the Cu sites. Notably, Ag@Cu2O-30 achieves a high C2H4/CH4 Faradaic efficiency ratio of 6.5 at −1.8 V (vs RHE) with an increased C2H4 partial current density of 12.3 mA cm–2. Oxidation to Ag@CuO further modifies the Cu species distribution, facilitating CO and CO2 diffusion while reducing H2 formation. Moreover, constructing Cu-BDC-MOF followed by electrochemical reconstruction generates additional oxygen vacancies and stabilizes Cu+ species, enhancing C2H4 selectivity and stability but with increased CH4 formation and reduced current density. This study highlights Ag–Cu tandem catalysis and structural regulation of Cu as effective strategies for achieving selective reduction of CO2 toward C2H4.
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CERAMICS INTERNATIONAL
·
2025
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IF 5.6
Yanlei Li,Haibo Ouyang,Cuiyan Li,Bohan Sun,Tianzhan Shen,Qianqian Chen
Hafnium carbide (HfC) nanomaterials hold significant potential for enhancing the performance of ultra-high temperature ceramic matrix composites. However, achieving the synergistic optimization of their mechanical and ablation resistance properties through controllable synthesis remains a challenge. To address this issue, this study employed a nickel-catalyzed pyrolysis method using hafnium tetrachloride (HfCl 4 ) and furfuryl alcohol as precursors. By precisely controlling the catalyst concentration within a carbon/carbon (C/C) preform, the controlled synthesis of HfC nanowires (HfC NWs ) with two distinct diameters (500 nm and 1000 nm) was successfully achieved. Subsequently, corresponding C/C-HfC-SiC composites (denoted as HS-1 and HS-2) were fabricated via the polymer impregnation and pyrolysis (PIP) process. The results demonstrate that the HS-1 composite modified with 500 nm HfC NWs exhibits the most superior performance: its flexural strength was significantly increased by 51.84 % compared to the unmodified sample, and it displayed the best ablation resistance after 60 s of exposure to an oxyacetylene flame. In-depth characterization revealed that this enhancement originates from the dense three-dimensional network formed by the finer nanowires, which effectively traps ceramic particles and facilitates the formation of a denser, more protective oxide layer. This work elucidates the critical role of nanowire diameter control and provides valuable insights for designing high-performance composites for extreme environments.
研究领域:
材料科学
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陶瓷基复合材料
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纳米材料
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高温材料工程
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ADVANCED MATERIALS
·
2026
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IF 29.1
Chao Peng,Xiong Wang,Lang Chen,Shuang-Feng Yin
Selective photocatalytic upgrading of glycerol to glycolaldehyde is intrinsically challenging because, under a conventional C–C cleavage scenario, the carbon-based selectivity of a C2 product is, in principle, capped at 66.67%. Here, a size-regulated Pd on TiO 2 platform as an efficient photocatalyst realized selective oxidation of glycerol into glycolaldehyde with selectivity up to 87.54%. As the Pd size increases from single atoms to nanoparticles, both glycerol conversion and glycolaldehyde selectivity increase monotonically, reaching 36.52% conversion and a glycolaldehyde formation rate of 12.05 mmol g ‒1 h ‒1 . Combined in situ spectroscopy, isotope-labeling experiments, and density functional theory calculations reveal that increasing Pd size switches glycerol adsorption from a symmetric terminal–terminal mode to an asymmetric terminal–secondary mode, thereby promoting C–C activation and enabling a radical-mediated cleavage-recoupling route toward glycolaldehyde. Isotopic liquid chromatography-mass spectrometry verifies C–C recombination after bond cleavage, which accounts for the glycolaldehyde selectivity exceeding the conventional 66.67% carbon limit, water as a direct contributor to •OH generation, and oxygen incorporation into the products. This work establishes a mechanistic framework in which metal size alters the interfacial adsorption geometry and reaction energy, thereby providing a general strategy for the selective photocatalytic valorization of polyol biomass molecules.
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GREEN CHEMISTRY
·
2023
·Vol. 25
·期 13
·5150-5159
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IF 9.8
Yuzhen Hu,Yanbin Cui,Shuoxiao Zhao,Xuelai Zhao,Xiaohong Hu,Zhenlong Song,Wei Fan,Qi Zhang
Selective cleavage of C–C bonds in the lignin structure is crucial for the depolymerization of lignin and producing value-added chemicals. In this study, we reported that Pd/CeO2 catalysts can selectively catalyze the Cα–Cβ bond cleavage of oxidized lignin model components and authentic lignin in an aqueous phase under mild conditions (50 °C, ambient pressure). A variety of β-O-4 and β-1 ketones with representative Cα–Cβ bonds were successfully cleaved yielding aromatic acids and phenols in 76.8–94.9% yields. Their unique catalytic properties are derived from the electron transfer between Pd and CeO2 support which facilitates active Pd2+ sites and reactive oxygen species formation. A mechanistic study elucidates that base-mediated C–H bond activation via enolization and in situ reactive oxygen species (˙O2−) formation are the key steps for the selective Cα–Cβ cleavage. Furthermore, the applicability of the system for the bond cleavage in an authentic lignin sample was demonstrated. Nearly 54.2 wt% of oxidized bamboo lignin was converted, generating aromatic monomer yields up to 35.9 wt%, with a high selectivity for aromatic aldehydes.
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PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
·
2023
·Vol. 120
·期 44
·e2307320120
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IF 11.1
Yangyang Yu,Ye He,Ping Yan,Shengyao Wang,Fan Dong
The selective photocatalytic conversion of CO2 and H2O to high value-added C2H4 remains a great challenge, mainly attributed to the difficulties in C–C coupling of reaction intermediates and desorption of C2H4* intermediates from the catalyst surface. These two key issues can be simultaneously overcome by alloying Ag with Cu which gives enhanced activity to both reactions. Herein, we developed a facile stepwise photodeposition strategy to load Cu–Ag alloy sub-nanoclusters (ASNCs) on TiO2 for CO2 photoreduction to produce C2H4. The optimized catalyst exhibits a record-high C2H4 formation rate (1110.6 ± 82.5 μmol g−1 h−1) with selectivity of 49.1 ± 1.9%, which is an order-of-magnitude enhancement relative to current work for C2H4 photosynthesis. The in situ FT-IR spectra combined with DFT calculations reveal the synergistic effect of Cu and Ag in Cu–Ag ASNCs, which enable an excellent C–C coupling capability like Ag and promoted C2H4* desorption property like Cu, thus advancing the selective and efficient production of C2H4. The present work provides a deeper understanding on cluster chemistry and C–C coupling mechanism for CO2 reduction on ASNCs and develops a feasible strategy for photoreduction CO2 to C2 fuels or industrial feedstocks.
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ADVANCED MATERIALS
·
2023
·
IF 29.4
Wenzheng Zhang,Mingyi Tan,Daming Chen,Boqian Sun,Yuan Cheng,Liancai Xun,Jingsheng Hu,Chenlin Hou,Yuxuan Liu,Yuhao Fang,Ping Hu,Wenbo Han,Shun Dong,Shanyi Du,Jiecai Han,Shuxi Miao,Qidong Yang,Yanchun Zhou,Xinghong Zhang
Sugars are renewable resources essential to human life, but they are rarely used as raw materials for the industrial production of carbon-based materials, especially for the preparation of carbon fiber-reinforced carbon-matrix (C/C) composites, which are extremely useful for the semiconductor and aerospace sectors. Herein, a method utilizing sugar-derived carbon to replace petrochemicals as dense matrix to preparing C/C composites is reported. The matrix from sugar-derived C/C (S–C/C) composites has a nanocrystalline graphite structure that is highly thermally stable and effectively bonded to the carbon fibers. The mechanical properties of the S–C/C composite are comparable to those prepared from petrochemical sources; significantly, it exhibits a linear ablation rate of 0.03 mm s −1 after 200 s of ablation at 3000 °C in 10 MW m −2 heat flux. This new class of S–C/C is promising for use in a broad range of fields, ranging from semiconductor to aerospace.
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Nature Ecology & Evolution
·
2023
·Vol. 7
·期 11
·1892-1902
·
IF 16.8
Ju Yun,Zhang Hong,Jiang Yanxiao,Wang Wenxin,Kan Guangfeng,Yu Kai,Wang Xiaofei,Liu Jilin,Jiang Jie
The reverse tricarboxylic acid cycle (rTCA) is a central anabolic network that uses carbon dioxide (CO 2 ) and may have provided complex carbon substrates for life before the advent of RNA or enzymes. However, non-enzymatic promotion of the rTCA cycle, in particular carbon fixation, remains challenging, even with primordial metal catalysis. Here, we report that the fixation of CO 2 by reductive carboxylation of succinate and α-ketoglutarate was achieved in aqueous microdroplets under ambient conditions without the use of catalysts. Under identical conditions, the aqueous microdroplets also facilitated the sequences in the rTCA cycle, including reduction, hydration, dehydration and retro-aldol cleavage and linked with the glyoxylate cycle. These reactions of the rTCA cycle were compatible with the aqueous microdroplets, as demonstrated with two-reaction and four-reaction sequences. A higher selectivity giving higher product yields was also observed. Our results suggest that the microdroplets provide an energetically favourable microenvironment and facilitate a non-enzymatic version of the rTCA cycle in prebiotic carbon anabolism.
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BIOMACROMOLECULES
·
2020
·
IF 6.092
Caicai Jiao,Lilong Gao,Hui Zhang,Bing Yu,Hailin Cong,Youqing Shen
Hydrogels have a wide range of applications in the fields of biomedicine, flexible electronics, and bionics. In this study, injectable and self-healable hydrogels were first prepared based on a dynamic covalent C═C bond formed via the Knoevenagel condensation reaction between poly(ethylene glycol) dicyanoacetate and water-soluble poly(vanillin acrylate). Three kinds of catalysts (phosphate buffer, zeolitic imidazolate framework-8, and tertiary amine) were used in Knoevenagel condensation for preparing hydrogels. All hydrogels in this study could be formed in situ, and their gelation time ranged from seconds to minutes. The properties and application of hydrogels could be customized according to the type of catalyst employed. 3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) results indicated that all the components and hydrogels exhibited low toxicity, and the hydrogels could be used as 3D cell culture scaffolds. Because of the dynamic covalent C═C bond formed by Knoevenagel condensation, the resultant hydrogels were found to be dynamic and showed good self-healing properties. This work presents a new dynamic covalent chemistry for the preparation of self-healable materials.
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ENERGY & FUELS
·
2025
·
IF 5.3
Ajibola T. Ogunbiyi,Wenzhi Li,Leyu Zhu,Amir Hamza,Jingting Jin
Despite lignin’s massive potential for biobased clean fuel production, developing effective catalysts for selectively cleaving its interunit bonds to harness this potential continues to be challenging. In this study, an HZSM-5-supported MoO3 catalyst was developed for a one-pot, hydrothermal kraft lignin depolymerization to maximize liquid fuel yield. A record-high 85.1% yield of petroleum ether-soluble product (a potential gasoline substitute), an unprecedented 45.3% yield of aromatic monomer, and a meager 4.9% char yield (corresponding to a 95.1% lignin conversion) were realized at 300 °C and 24 h in a catalytic transfer hydrogenolysis. The resulting liquid fuel afforded a calorific value of 35.97 MJ/kg, significantly improving over the 25.45 MJ/kg in the original kraft lignin. Catalyst characterization results showed that an optimal acidity characteristic and a suitable Mo-zeolite interaction were pivotal to the efficient cleavage of the C–O and C–C bonds in the kraft lignin. The analyses of the spent catalyst revealed that the formation of inactive Mo4+ species and carbonaceous deposits on the catalyst’s surface was responsible for the initial catalyst deactivation, but recalcination reinstated the catalyst activity. This study extends the frontiers of knowledge in rational catalyst development for lignin valorization applications.
研究领域:
催化化学
·
生物质能
·
可再生能源
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Journal of Environmental Chemical Engineering
·
2026
·Vol. 14
·期 5
·124602
·
IF 7.5
Yunyi Wang,Ru Yang,Xiang Li,Haiping Wang,Ting Wu,Guigan Fang
Photocatalytic cleavage of lignin C–C bonds using graphitic carbon nitride (g-C 3 N 4 ) offers a sustainable route to aromatic monomers; however, its practical efficiency is critically constrained by the generation yield of superoxide radicals. Herein, we address this constraint through a simple yet effective design: replacing the edge amino groups of g-C 3 N 4 with benzene rings to construct a benzene–g-C 3 N 4 copolymer. DFT calculations suggest that the introduced benzene ring contributes an empty low-lying orbital that may serve as a temporary electron trap. This effect, together with in-situ XPS evidence for photo-induced charge redistribution, is consistent with the formation of an S-scheme charge transfer pathway and the observed suppression of picosecond-scale electron–hole recombination. The benzene ring is proposed to function as a π–π adsorption anchor, selectively binding the lignin C β carbocation in close proximity to the C–N = C sites where superoxide radicals are generated. This directed adsorption overcomes the mass-transfer limitation of superoxide radical typically encountered under chemisorption conditions, thereby enabling spontaneous and diffusion-free oxidation of the C β site. This benzene–g-C 3 N 4 copolymer exhibits a 134% higher reaction efficiency than g-C 3 N 4 in C–C bond photocleavage, while also demonstrating excellent cleavage performance on industrial lignin. Collectively, this work offers an effective approach to overcoming kinetic limitations in photocatalysis.
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ACS Catalysis
·
2026
·
IF 13.6
Huating Jiang,Zhiruo Guo,Xiaohui Liu,Yong Guo,Yanqin Wang
Lignin represents the most abundant source of aromatic compounds in nature, and its depolymerization holds great promise for yielding valuable aromatic products. Herein, we demonstrate the photocatalytic oxidative cleavage of β–1 bonds via the the Mars–van Krevelen (MvK) mechanism, and catalytic activity is achieved over lattice oxygen (OL)-rich WO3. A conversion of 99% is reached after reaction for 2 h under visible light, with the selectivity to benzaldehyde and benzoic acid reached 94%, surpassing the most reported catalytic systems. This photocatalytic performance stems from precise modulation of OL and oxygen vacancies (OV) sites in WO3, applicable to diverse β–1 model compounds and industrial lignin. In this MvK mechanism, the substrate adsorbs onto the OL sites, followed by activating the Cβ−H and inserting the lattice oxygen into the C–H bond to form a benzoin intermediate. Then, the desorbed benzoin undergoes a a Norrish Type I-like reaction, breaking the C–C bonds to form benzaldehyde. Concurrently, the adsorbed O2 at OV sites is reduced by photogenerated electrons, replenishing the depleted lattice oxygen and therefore manifesting stability (10 cycles). This in situ removal–regeneration strategy provides an approach for efficient lignin C−C bond cleavage and establishes the rational design principles for interfacial photocatalysts toward lignin valorization.
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