基于扩散强化的Pickering界面生物催化系统构建及CO2矿化过程研究

CO₂的有效利用有助于解决环境和生态问题.碳酸酐酶(CA)等酶分子可精准活化CO₂分子以降低反应能垒,为CO₂的高效和高选择性转化提供了一种有前景的途径.然而,酶离开生物体后易失活,且难以重复利用.目前,包埋型固定化酶是常用且有效的提高酶稳定性与回用率的方法之一,但载体的存在会造成反应物CO₂内扩散阻力增加,降低反应活性.此外,CO₂酶促转化是一个气-液-固三相反应过程,反应体系中CO₂的外扩散性能也需要加强.金属有机骨架(MOFs),特别是咪唑酯骨架(ZIFs),常被用作酶固定化的载体.ZIFs的拓扑结构可被设计成不同形貌,进而通过ZIFs的结构工程来加强分子向其中的内扩散.Pickering乳液是指以固体颗粒代替常规表面活性剂而稳定的乳液.当固体颗粒具有催化活性时,催化剂颗粒会扩大液-液-固或气-液-固三相接触面积,从而有效协调反应物在不同相中的扩散时间.如果酶被用作这些颗粒的活性中心,所制备的Pickering乳液也可能具备类似的特性,可加强底物分子向酶的外扩散.本文选择两种具有不同结构的ZIFs(ZIF-L和ZIF-8),原位包埋CA后形成CA@ZIFs颗粒以稳定Pickeirng乳液.ZIF-L和CA@ZIF-L颗粒显示出独特的二维层状堆叠结构.ZIF-8和CA@ZIF-8颗粒呈棱角清晰的十二面体结构.与CA@ZIF-8颗粒相比,CA@ZIF-L颗粒显示出更大的孔径和更宽的孔径分布,这有助于CO₂从CA@ZIF-L颗粒表面扩散至酶活性中心.利用酶活测试来研究内扩散是否通过结构工程得到了加强,发现CA@ZIF-L颗粒的活性比CA@ZIF-8颗粒高22.3%,推测这是由于CA@ZIF-L颗粒特殊的十字花状结构会缩短CO₂从颗粒表面扩散至酶活性中心的距离.同时,十字花状结构可暴露更多的酶活性位点(CA@ZIF-L颗粒的暴露面积是CA@ZIF-8颗粒的~8倍),从而提升了反应物浓度并显示出更高的催化活性.本文还设计了吸附实验来进一步验证上述假设,发现BSA@ZIF-L颗粒对香豆素的吸附率远高于BSA@ZIF-8颗粒,说明与ZIF-8相比,酶包埋于ZIF-L具有更强的捕获小分子的能力,表明CO₂分子向CA@ZIF-L的扩散速度更快,即CA@ZIF-L的十字花状结构可强化系统的内扩散过程.进一步比较了PIBS和游离多酶体系的催化活性,将CO₂通入每个系统,在反应前20 min,PIBS的pH值下降速度比游离体系快得多,说明PIBS通过在气相和液相间构建更大的界面,缩短了CO₂向CA的扩散距离,从而提高了催化效率,促进了CO₂转化.上述假设也通过扩散动力学的计算得到了验证.为进一步研究PIBS的CO₂矿化能力,本文开展了CaCO₃矿化反应,发现PIBS的CaCO₃产量远高于游离多酶体系,表明构建的PIBS在强化内外扩散方面具有显著优势.最后,评估了PIBS在工业应用中的性能,由CA@ZIF-L和CA@ZIF-8颗粒构建的PIBS显示出较好的可回收性,在第8个循环后,PIBS仍可保持8.9 mg/5 min的CaCO₃产量.综上,PIBS可为CO₂的酶促转化和框架提供一个新方法和新平台.     

A new fluorescent quinoline derivative toward the acid-responsivity in both solution and solid states

In this article, an acid-responsive luminescent material, 1,4-di(quinoline-6-yl)buta-1,3-diyne (DQBD) is designed and synthesized. Upon different pH values, gradual changes of fluorescence colors for DQBD in both solution and solid phases are demonstrated due to the protonation effect. Moreover, such responsive characteristics can also be reversible, suggesting DQBD as a promising fluorescent material with great potential for reusable- and accurate-pH sensors in the future.     

基于α-溴代酮的催化不对称合成3,3-螺环丙基吲哚酮和乙烯基环丙烷

在甲基化奎尼丁(20mol%)的催化下,分别实现了α-溴代酮与3-(取代亚甲基)吲哚酮和缺电子1,3-二烯的高度非对映选择性和对映选择性的环丙烷化反应,以46%~99%收率、高达98%ee和20∶1 dr生成相应的3,3-螺环丙基吲哚酮和乙烯基环丙烷.通过催化的氮叶立德策略,成功发展了一种用于上述手性化合物的简便合成方法.     

All Organic Sodium‐Ion Batteries with Na4C8H2O6

Developing organic compounds with multifunctional groups to be used as electrode materials for rechargeable sodium‐ion batteries is very important. The organic tetrasodium salt of 2,5‐dihydroxyterephthalic acid (Na₄DHTPA; Na₄C₈H₂O₆), which was prepared through a green one‐pot method, was investigated at potential windows of 1.6–2.8 V as the positive electrode or 0.1–1.8 V as the negative electrode (vs. Na⁺/Na), each delivering compatible and stable capacities of ca. 180 mAh g^?1 with excellent cycling. A combination of electrochemical, spectroscopic and computational studies revealed that reversible uptake/removal of two Na⁺ ions is associated with the enolate groups at 1.6–2.8 V (Na₂C₈H₂O₆/Na₄C₈H₂O₆) and the carboxylate groups at 0.1–1.8 V (Na₄C₈H₂O₆/Na₆C₈H₂O₆). The use of Na₄C₈H₂O₆ as the initial active materials for both electrodes provided the first example of all‐organic rocking‐chair SIBs with an average operation voltage of 1.8 V and a practical energy density of about 65 Wh kg^?1.     

[HCo(CO)4]‐Catalyzed Three‐component Cycloaddition of Epoxides,Imines, and Carbon Monoxide: Facile Construction of 1,3‐Oxazinan‐4‐ones

The three‐component [3+2+1] cycloaddition of epoxides, imines, and carbon monoxide to produce 1,3‐oxazinan‐4‐ones has been developed by using [HCo(CO)₄] as the catalyst. The reaction occurs for a wide variety of imines and epoxides, under 60 bar of CO pressure at 50 °C, to produce 1,3‐oxazinan‐4‐ones with different substitution patterns in high yields, and provides an efficient and atom‐economic route to heterocycles from simple and readily available starting materials. A plausible mechanism involves [HCo(CO)₄]‐induced ring‐opening of the epoxide, followed by sequential addition of carbon monoxide and the imine, and then ring closure to form the product accompanied by regeneration of [HCo(CO)₄].     

MoS2 Nanoflowers with Expanded Interlayers as High‐Performance Anodes for Sodium‐Ion Batteries

MoS₂ nanoflowers with expanded interlayer spacing of the (002) plane were synthesized and used as high‐performance anode in Na‐ion batteries. By controlling the cut‐off voltage to the range of 0.4–3 V, an intercalation mechanism rather than a conversion reaction is taking place. The MoS₂ nanoflower electrode shows high discharge capacities of 350 mAh g^?1 at 0.05 A g^?1, 300 mAh g^?1 at 1 A g^?1, and 195 mAh g^?1 at 10 A g^?1. An initial capacity increase with cycling is caused by peeling off MoS₂ layers, which produces more active sites for Na⁺ storage. The stripping of MoS₂ layers occurring in charge/discharge cycling contributes to the enhanced kinetics and low energy barrier for the intercalation of Na⁺ ions. The electrochemical reaction is mainly controlled by the capacitive process, which facilitates the high‐rate capability. Therefore, MoS₂ nanoflowers with expanded interlayers hold promise for rechargeable Na‐ion batteries.     

Origins of the Enantio‐ and N/O Selectivity in the Primary‐Amine‐Catalyzed Hydroxyamination of 1,3‐Dicarbonyl Compounds with In‐Situ‐Formed Nitrosocarbonyl Compounds: A Theoretical Study

Chemoselective control over N/O selectivity is an intriguing issue in nitroso chemistry. Recently, we reported an unprecedented asymmetric α‐amination reaction of β‐ketocarbonyl compounds that proceeded through the catalytic coupling of enamine carbonyl groups with in‐situ‐generated carbonyl nitroso moieties. This process was facilitated by a simple chiral primary and tertiary diamine that was derived from tert‐leucine. This reaction featured high chemoselectivity and excellent enantioselectivity for a broad range of substrates. Herein, a computational study was performed to elucidate the origins of the enantioselectivity and N/O regioselectivity. We found that a bidentate hydrogen‐bonding interaction between the tertiary N⁺? H and nitrosocarbonyl groups accounted for the high N selectivity, whilst the enantioselectivity was determined by Si‐facial attack on the (E)‐ and (Z)‐enamines in a Curtin–Hammett‐type manner. The bidentate hydrogen‐bonding interaction with the nitrosocarbonyl moieties reinforced the facial selectivity in this process.     

Taming Living Carbocations in Catalytic Direct Conjugate Addition of Simple Alkenes to α,β‐Enones

A Lewis acid in the presence of an anionic phosphate ligand enables the addition of alkenes to α,β‐enones. The ligand facilitates selective β‐proton elimination by suppressing competing pathways, thus leading to vinylation adducts in high yields (up to 99 %) for a broad range of substrates.     

A Supramolecular Tubular Nanoreactor

The extremely strong noncovalent complexation between the rigid host of phthalocyanine‐bridged β‐cyclodextrins and the amphiphilic guest carboxylated porphyrin is employed to construct a hollow tubular structure as a supramolecular nanoreactor. A representative coupling reaction occurs in the hydrophobic interlayers of the tubular walls in pure water at room temperature, leading to an enhancement of ten times higher reaction rate without any adverse effect on catalytic activity and conversion.     

Podand‐Based Dimeric Chromium(III)–Salen Complex for Asymmetric Henry Reaction: Cooperative Catalysis Promoted by Complexation of Alkali Metal Ions

A new kind of podand‐based dimeric salen ligand was synthesized, and its association with potassium cations was investigated by ¹H NMR spectroscopy. The corresponding Cr^III–salen dimer was assembled by a supramolecular host–guest self‐assembly process and was then used as a catalyst in highly efficient and enantioselective asymmetric Henry reactions. Regulation by KBAr_F (BAr_F=[3,5‐(CF₃)₂C₆H₃]₄B) led to remarkable improvements in yield (by up to 58 %) and enantioselectivity (for example, from 80 % ee to 96 % ee).