基于壳聚糖二氧化碳智能材料

二氧化碳(CO₂)捕获以及转化是控制大气中二氧化碳含量和有效利用的主要策略。CO₂ 响应型聚合物以含有胺基的烯类单体为主要原料,通过接枝聚合或与其他功能分子复合来改善其对CO₂的响应以及捕获性能。其中,天然高分子(如多糖、蛋白质等)具有资源丰富、无毒、可降解和良好的生物相容性等优点,是制备环境友好高分子材料的最佳选择。同时,壳聚糖含有大量的伯胺,在制备基于胺基的具有CO₂响应以及捕获性能的智能复合材料中具有潜在优势。本文首先介绍了CO₂响应聚合物和壳聚糖的特点,进一步归纳了近年来基于壳聚糖的CO₂响应高分子以及捕获材料的最新研究进展,并对这类复合材料的设计及其应用前景进行了展望。     

CO2/C2H4耦合制备丙烯酸及其衍生物的研究进展

二氧化碳(CO₂)不仅仅是一种温室气体,更是一种重要的、有效的碳一资源,其来源丰富、无毒、无污染、不易燃烧,可用于生产有机化学品、材料、糖类等.由于CO₂分子中的碳处于最高氧化态,且其分子具有热力学和动力学惰性,因此人们不断探索新型反应途径,以及新型的催化体系来有效资源化利用CO₂.近年来,利用各种不饱和烃类,在过渡金属催化剂协助下催化CO₂与烯烃生成不饱和羧酸及其衍生物引起了极大关注.其中,催化CO₂/C₂H₄耦合反应制备丙烯酸及其衍生物因其原子经济性而备受瞩目.以镍系催化体系为主的过渡金属催化CO₂/C₂H₄偶联反应是CO₂化学转化与高值利用非常重要的研究热点之一.综述了近年来CO₂/C₂H₄偶联反应的最新进展,对相应的催化反应机理进行了评述.从多个角度对各位学者的研究进行分析比...     

固体氧化物电解池直接电解CO2的研究进展

固体氧化物电解池是一种高效、环境友好型的能量转换器件,可以直接将电能转化为化学能. 本文介绍了近年来作者课题组在固体氧化物电解池直接用于CO₂还原的研究进展,并以阴极材料为主着重讨论了金属陶瓷电极和混合导电型钙钛矿氧化物电极的研究工作,最后展望了未来固体氧化物电解池直接电解CO₂的研究思路和方向.     

共价有机框架材料在光催化CO2还原中的应用

全球范围内化石燃料的大量消耗导致了能源危机,同时其所排放的CO₂等温室气体使环境问题日渐突出。将CO₂等废气进一步转化为高附加值燃料是解决能源与环境问题的理想方案。利用取之不尽的太阳能作为能源实现光催化CO₂还原为能源化合物被认为是有效解决此问题的最佳途径之一。共价有机框架材料(COFs)是一类新型晶态多孔有机聚合物材料,具有结构稳定性、可设计性和结构多样化的特征,因此在光催化CO₂还原领域表现出了巨大潜力。本文概述了近年来COFs在光催化CO₂还原领域中的催化应用研究进展,包括引入不同金属离子提供活性位点、增加光敏性官能团提高其对可见光利用率等方法。最后对以COFs材料为光催化CO₂还原催化剂的研究进行了总结和展望,我们认为更进一步的新材料合成、修饰与催化机理研究仍是前景广阔的研究领域。     

金属-有机框架基材料在二氧化碳光催化转化中的应用

将大气中的二氧化碳(CO₂)转化为燃料或高附加值化学品是降低大气中CO₂含量、 减缓温室效应的有效途径之一. 光催化CO₂化学转化条件温和, 能耗低, 在CO₂转化中占有重要地位. 金属-有机框架(MOF)基材料由于具有比表面积大、 光电性质优良和可调节性强等特点, 是CO₂光催化转化的常用催化剂之一. 本文综合评述了近两年MOF基材料在光催化CO₂还原反应、 CO₂环加成反应和CO₂羧基化反应中的应用, 阐释了MOF基材料在CO₂光催化转化中的优势和局限性, 并展望了其未来发展.     

二氧化碳刺激响应的荧光传感器*

CO₂刺激响应聚合物作为一种智能刺激响应材料,因其在可逆的调控过程中通常只涉及CO₂气体的通入和排出而具有广泛的应用前景。CO₂荧光传感器是将CO₂的浓度变化转化为可检测到的荧光信号,可实现对CO₂浓度的实时监测和可逆调控,也有助于我国如期实现2030年前碳达峰和2060年前碳中和的生态文明建设目标。本文简要介绍CO₂刺激响应物质的基本原理和常见分类方式,阐述该类物质在构筑荧光传感器方面的妙用,围绕响应灵敏性、响应速率、循环使用性和抗干扰性等传感性能指标的研究成果进行讨论。最后对CO₂刺激响应荧光传感器的改进方向和应用前景进行了展望。     

双中心多孔聚合物作为多相催化剂实现CO2在温和条件下高效转化

由于对化石燃料的高度依赖和二氧化碳(CO₂)的过度排放,大气中CO₂浓度从280 ppm上升到400 ppm左右,导致全球变暖和其他气候问题.在这种情况下,如何有效降低空气中的CO₂浓度成为近年来最迫切的研究领域之一.另一方面,作为一种无毒、廉价且丰富的C1资源,CO₂也可以转化为各种高附加值的工业产品,如甲酸、一氧化碳、甲烷、甲醇以及碳酸酯等.其中CO₂与环氧化物转化生成环碳酸酯的环加成反应具有良好原子经济性,在近年来引起了人们的广泛关注.尽管已有多种多相和均相催化剂应用于该反应,但已有的催化剂特别是多相催化剂往往具有反应条件苛刻、催化剂易损失以及需要可溶性的共催化剂等缺点,从而限制了它们的进一步实际应用.因此,发展多相催化剂实现在温和和无共催化剂条件下的CO₂环加成转化仍是一个挑战.本文通过自由基共聚的方法,以乙烯基功能化的金属卟啉和季膦盐作为单体制备了一种新型多孔有机聚合物(POP-PBnCl-TPPMg-x).考虑到金属卟啉和季膦盐常作为CO₂环加成反应中的Lewis酸和Lewis碱活性中心,我们通过自由基共聚实现了这两种活性中心在分子水平上的结合与协同.所得的催化剂的组成和结构通过固体核磁、X射线光电子能谱、氮气吸附、扫描电子显微镜、透射式电子显微镜等手段进行了表征.值得指出的是,所得多相催化剂具有良好的CO₂吸附与富集效应,十分有利于CO₂的催化转化.我们以温和(40℃和1 atm CO₂)并没有任何无可溶性共催化剂存在条件下,进行CO₂与环氧化物的环加成作为探针反应,测试了不同催化剂的催化活性.以催化剂POP-PBnCl-TPPMg-12为例,其催化活性远超过单组分的POP-PBnCl和POP-TPPMg多相催化剂,也超过了二者机械混合的POP-PBnCl+POP-TPPMg-12催化剂,接近均相催化剂PBnCl+TPPMg-12的水平.这表明通过共聚合方法所得到的催化剂可以实现Lewis酸和Lewis碱两种活性中心的分子水平的结合.本文进一步研究了多相催化剂POP-PBnCl-TPPMg-12和均相催化剂PBnCl+TPPMg-12在低浓度CO₂(15%N2 v/v,工业废气中CO₂的浓度)条件下的催化活性,发现在该条件下多相催化剂表现出比均相催化剂更为优异的催化转化性能,且展现出良好的稳定性和循环使用性能,在循环使用5次后仍无明显的活性损失.该催化剂所具有的多相特点和优良的催化性能,因而有望成为实现工业CO₂脱除并转化成高附加值产品的潜在高效催化剂.     

多孔骨架固定分子催化剂催化CO2加氢制备甲酸研究进展

近年来, 大气中CO₂含量急剧增加, 导致了严重的温室效应. 将CO₂作为C1资源转化为燃料或精细化学品引起了越来越多的关注. 开发高效、 稳定、 可回收利用的催化剂成为CO₂资源化利用的关键. 在众多的CO₂加氢催化剂中, 功能性多孔骨架材料固定型分子催化剂展示出优异的性能, 成为研究的热点之一. 功能性骨架材料, 如多孔有机聚合物(POPs)、 共价有机骨架(COFs)和金属有机骨架(MOFs), 具有比表面积大、 热稳定性高和可调性等特点, 在设计合成催化剂方面发挥着重要作用. 本文介绍了POPs/COFs/MOFs多孔骨架材料固定分子催化剂的开发及在催化CO₂合成甲酸领域的最新进展.     

铜催化磷酰基叠氮参与的三组分聚合制备聚膦酰基脒

为进一步发展高效的多组分聚合方法,构建有应用前景的高分子材料,本文报道了一种基于一价铜催化的,以叠氮磷酸二苯酯(DPPA)、二炔和二胺为单体的多组分聚合方法,在N,N-二甲基甲酰胺(DMF)中室温反应4 h,制备了一系列聚膦酰基脒,产率高达90%,重均分子量高达54000 g/mol,仅生成氮气为副产物.DPPA参与聚合具有后修饰的潜在应用,克服传统磺酰基叠氮后修饰困难的缺点.以含缩硫酮的二胺为聚合单体可制备具有特殊结构、活性氧敏感的聚膦酰基脒,在活性氧刺激下实现聚合物的降解.通过核磁共振波谱,凝胶色谱及基质辅助激光解吸飞行时间质谱确定聚合物结构、分子量及重复单元,并研究了炔类单体的刚柔性和胺类单体的位阻效应对聚合反应的影响.该聚合方法为多组分聚合提供了一种新的途径,拓宽了高分子材料的应用范围,为下阶段探索聚脒材料的应用奠定基础.     

理论设计和实验研究吡啶掺杂聚合氮化碳提升光催化CO2还原性能(英文)

光催化CO₂还原是利用太阳光和水将CO₂转化为高价值化学品或燃料(如CO、甲醇、甲烷等),被认为是解决CO₂问题的理想途径之一.CO₂分子中C=O离解能高而活化困难,且光催化CO₂还原涉及多质子耦合多电子转移过程且产物多样,因而研制效率高且选择性好的光催化剂是该技术的关键.聚合物氮化碳(PCN)作为一种结构可调的有机光催化剂,具有化学稳定性好且能带位置适宜于还原CO₂的优势,是一种具有发展潜力的CO₂还原光催化剂;但是PCN也存在因其禁带宽度较大而对可见光响应范围有限以及因其结构由三均三嗪单元构成而缺乏足够活性位点来吸附和活化CO₂等不足.目前在提升PCN的光催化CO₂还原性能方面已有不少研究,但所得的PCN基光催化剂在效率和选择性上仍处于较低水平.考虑到光催化CO₂还原涉及复杂的热力学和动力学要求,对基于PCN的光催化剂进行精准设计和研究是非常必要的,这有望获得同时具...     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.