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金属有机骨架(MOF)材料由于其孔隙率高、比表面积大以及具有发达的内联通孔道结构等优点,可以作为优良的生物分子固定化载体。通过表面活性自组装策略制备了铈基介孔MOF(Ce-MOF-F),表征结果表明,该材料有大的比表面积和呈辐射状的介孔孔道结构。以其为载体、南极假丝酵母脂肪酶B(CALB)为模型酶,通过物理吸附法制备了生物催化剂CALB@Ce-MOF-F,对该固定化酶的酶载量和催化性能进行了研究。在优化条件下,CALB的负载量为162.0mg/g载体,水解活性为899.1U/g蛋白。与游离CALB相比,CALB@Ce-MOF-F表现出对高温、酸碱和有机溶剂等有更强的耐受性;将Ce-MOF-F用于多种酶的固定化,研究其作为载体的普适性,结果表明,介孔Ce-MOF-F对洋葱伯克氏菌脂肪酶(BCL)和漆酶有良好的固定效果,可以作为良好载体,并能对酶起到较好的保护作用。 相似文献
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负载型Au催化剂因其在诸多反应过程中的高催化活性而备受研究者关注.然而针对负载型催化剂中Au物种结构的有效调控,以及催化过程中真实构-效关系的探索一直充满了挑战.用CeO2为Au物种担载基底,通过简单煅烧处理引起的CeO2结构变化,进而实现Au/CeO2之间界面作用力的调控.此研究发现Au纳米颗粒中Au0物种具备更为高效的催化室温CO氧化活性,结合多种原位表征分析,其室温条件下催化转化效率更依赖于CO吸附能力.而相比于单原子Au1和纳米Au颗粒,所制备的团簇Au/CeO2催化剂在较高温度(>50℃)展现出优异的催化CO氧化反应性能.随着温度升高,催化剂表界面O参与的MvK反应路径更易发生,因此具有更多表界面活性O物种和Auδ+位点的团簇Au/CeO2催化剂展现出最为优异的催化CO氧化性能.这些发现为高效负载型Au催化剂的制备提供了新思路并深化了对Au/CeO2催化作用机制的理解. 相似文献
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从空间位阻角度出发,设计并合成了H型芴基小分子材料3Ph-TrH,并通过溶液加工方法制备了将其作为电荷捕获层的浮栅型有机场效应晶体管(OFET)存储器.结果表明,该器件的空穴和电子存储窗口分别为31.2和11.6V,实现了基于单个小分子材料的双极性电荷存储.为了提高器件的稳定性,进一步制备了基于3Ph-TrH与聚苯乙烯(PS)掺杂薄膜的浮栅型OFET存储器.测试结果显示,该器件比基于3Ph-TrH作为单组分电荷捕获层的器件具有更高的稳定性和耐受性,在10000s的维持时间测试后,该器件的电流开关比还能维持在1.1×103.该工作为制备新型双极性电荷存储的OFET存储器提供了一条思路. 相似文献
106.
甲醇制烃(MTH)反应作为一条非石油可持续路线制备重要的平台化学品,得到学术界和工业界的广泛关注.根据主要产物的不同, MTH反应又分为甲醇制烯烃(MTO)、甲醇制汽油(MTG)和甲醇制芳烃(MTA).MTO反应已经实现了商业化应用,但其催化效率,即烯烃选择性和催化剂寿命仍有待提高.为开发高效的MTH催化剂,其机理研究得到了研究者的广泛关注.MTH反应稳态阶段的间接机理(即“烃池”机理)已达成基本共识,但反应诱导期的第一个C-C键的形成及转化过程一直是该领域具挑战性和争议性的课题.原位谱学技术的发展为探究MTH反应第一个C-C键的形成机理研究带来了机遇,目前,已有多条关于C-C键形成及转化路径的报道.然而,有关MTO反应机理,尤其是第一个C-C键形成及转化为“烃池”物种过程的报道和文献总结尚不充分.此外,有关机理研究用于指导高效MTO催化剂设计的文献综述较少.基于该反应重要的基础及应用研究背景,对其进行全面分析总结具有十分重要的意义.本文首先归纳总结了MTH反应的机理研究进展,包括第一个C-C键形成的直接机理、间接机理、“双循环”机理(提出及演变过程)以及由直接机理逐步转化为间接机理的... 相似文献
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生物质碳基材料具有可调的微观结构、丰富的表面活性中心、优良的导电和导热性能以及较大的比表面积,已经成为新能源领域的重要基础材料.然而,应用于锌-空气电池中时,碳基材料高电位下的碳腐蚀问题严重影响了电池的稳定性,因此,开发具有低过电位的析氧反应(OER)催化剂来降低充电电压是解决该问题的关键.本课题组采用一种低温磷化策略制备了具有低OER过电位的P修饰的Fe3O4/Fe2N和生物质碳复合催化剂(P-Fe3O4/Fe2N@NPC),其具有较好的双功能氧反应活性,氧还原反应(ORR)的半波电位为0.86 V,仅需要280 m V的OER过电位就可以达到10 m Acm-2的电流密度.以P-Fe3O4/Fe2N@NPC作为正极组装的锌-空气电池表现出低的充放电电压差和长期稳定性,在目前报道的碳基催化剂应用于锌-空气电池中具有很大优势.此外,采用X射线光电子能谱(XPS)、拉曼光... 相似文献
109.
Shaopeng Li Jing Du Bin Zhang Yanzhen Liu Qingqing Mei Qinglei Meng Minghua Dong Juan Du Zhijuan Zhao Lirong Zheng Buxing Han Meiting Zhao Huizhen Liu 《物理化学学报》2023,38(10):2206019
Selective hydrogenation is a vital class of reaction. Various unsaturated functional groups in organic compounds, such as aromatic rings, alkynyl (C≡C), carbonyl (C=O), nitro (-NO2), and alkenyl (C=C) groups, are typical targets in selective hydrogenation. Therefore, selectivity is a key indicator of the efficiency of a designed hydrogenation reaction. 5-(Hydroxymethyl)furfural (HMF) is an important platform compound in the context of biomass conversion, and recently, the hydrogenation of HMF to produce fuels and other valuable chemicals has received significant attention. Controlling the selectivity of HMF hydrogenation is paramount because of the different reducible functional groups (C=O, C-OH, and C=C) in HMF. Moreover, the exploration of new routes for hydrogenating HMF to valuable chemicals is becoming attractive. 5-Methylfurfural (MF) is also an important organic compound; thus, the selective hydrogenation of HMF to MF is an essential synthetic route. However, this reaction has challenging thermodynamic and kinetic aspects, making it difficult to realize. Herein, we propose a strategy to design a highly efficient catalytic system for selective hydrogenation by exploiting the synergy between steric hindrance and hydrogen spillover. The design and preparation of the Pt@PVP/Nb2O5 catalyst (PVP = polyvinyl pyrrolidone; Nb2O5 = niobium(V) oxide) were also conducted. Surprisingly, HMF could be converted to MF with 92% selectivity at 100% HMF conversion. The reaction pathway was revealed through the combination of control experiments and density functional theory calculations. Although PVP blocked HMF from accessing the surface of Pt, hydrogen (H2) could be activated on the surface of Pt due to its small molecular size, and the activated H2 could migrate to the surface of Nb2O5 through a phenomenon called H2 spillover. The Lewis acidic surface of Nb2O5 could not adsorb the C=O group but could adsorb and activate the C-OH group of HMF; therefore, when HMF was adsorbed on Nb2O5, the C-OH groups were hydrogenated by the spilled over H2 to form MF. The high selectivity of this reaction was realized because of the unique combination of steric effects, hydrogen spillover, and tuning of the electronic states of the Pt and Nb2O5 surfaces. This new route for producing MF has great potential for practical application owing to its discovered advantages. We believe that this novel strategy can be used to design catalysts for other selective hydrogenation reactions. Furthermore, this study demonstrates a significant breakthrough in selective hydrogenation, which will be of interest to researchers working on the utilization of biomass, organic synthesis, catalysis, and other related fields.
相似文献
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Industrialization undoubtedly boosts economic development and improves the standard of living; however, it also leads to some serious problems, including the energy crisis, environmental pollution, and global warming. These problems are associated with or caused by the high carbon dioxide (CO2) and sulfur dioxide (SO2) emissions from the burning of fossil fuels such as coal, oil, and gas. Photocatalysis is considered one of the most promising technologies for eliminating these problems because of the possibility of converting CO2 into hydrocarbon fuels and other valuable chemicals using solar energy, hydrogen (H2) production from water (H2O) electrolysis, and degradation of pollutants. Among the various photocatalysts, silicon carbide (SiC) has great potential in the fields of photocatalysis, photoelectrocatalysis, and electrocatalysis because of its good electrical properties and photoelectrochemistry. This review is divided into six sections: introduction, fundamentals of nanostructured SiC, synthesis methods for obtaining nanostructured SiC photocatalysts, strategies for improving the activity of nanostructured SiC photocatalysts, applications of nanostructured SiC photocatalysts, and conclusions and prospects. The fundamentals of nanostructured SiC include its physicochemical characteristics. It possesses a range of unique physical properties, such as extreme hardness, high mechanical stability at high temperatures, a low thermal expansion coefficient, wide bandgap, and superior thermal conductivity. It also possesses exceptional chemical characteristics, such as high oxidation and corrosion resistance. The synthesis methods for obtaining nanostructured SiC have been systematically summarized as follows: Template growth, sol-gel, organic precursor pyrolysis, solvothermal synthesis, arc discharge, carbon thermal reduction, and electrospinning. These synthesis methods require high temperatures, and the reaction mechanism involves SiC formation via the reaction between carbon and silicon oxide. In the section of the review involving the strategies for improving the activity of nanostructured SiC photocatalysts, seven strategies are discussed, viz., element doping, construction of Z-scheme (or S-scheme) systems, supported co-catalysts, visible photosensitization, construction of semiconductor heterojunctions, supported carbon materials, and construction of nanostructures. All of these strategies, except element doping and visible photosensitization, concentrate on enhancing the separation of holes and electrons, while suppressing their recombination, thus improving the photocatalytic performance of the nanostructured SiC photocatalysts. Regarding the element doping and visible photosensitization strategies, element doping can narrow the bandgap of SiC, which generates more holes and electrons to improve photocatalytic activity. On the other hand, the principle of visible photosensitization is that photo-induced electrons move from photosensitizers to the conduction band of SiC to participate in the reaction, thus enhancing the photocatalytic performance. In the section on the applications of nanostructured SiC, photocatalytic H2 production, pollutant degradation, CO2 reduction, photoelectrocatalytic, and electrocatalytic applications will be discussed. The mechanism of a photocatalytic reaction requires the SiC photocatalyst to produce photo-induced electrons and holes during irradiation, which participate in the photocatalytic reaction. For example, photo-induced electrons can transform protons into H2, as well as CO2 into methane, methanol, or formic acid. Furthermore, photo-induced holes can convert organic waste into H2O and CO2. For photoelectrocatalytic and electrocatalytic applications, SiC is used as a catalyst under high temperatures and highly acidic or basic environments because of its remarkable physicochemical characteristics, including low thermal expansion, superior thermal conductivity, and high oxidation and corrosion resistance. The last section of the review will reveal the major obstacles impeding the industrial application of nanostructured SiC photocatalysts, such as insufficient visible absorption, slow reaction kinetics, and hard fabrication, as well as provide some ideas on how to overcome these obstacles.
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