Cu(II) immobilized on mesoporous organosilica as an efficient and reusable nanocatalyst for one‐pot Biginelli reaction under solvent‐free conditions

Cu(II) immobilized on mesoporous organosilica nanoparticles (Cu²⁺@MSNs‐(CO₂^?)₂) has been synthesized, as a inorganic–organic nanohybrid catalyst, through a post‐grafting approach. Its characterization is carried out by Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Energy dispersive X‐ray (EDX), Thermogravimetric/differential thermal analyses (TGA‐DTA), and Nitrogen adsorption–desorption analysis. Cu²⁺@MSNs‐(CO₂^?)₂ exhibits high catalytic activity in the Biginelli reaction for the synthesis of a diverse range of 3, 4‐dihydropyrimidin‐2(1H)‐ones, under mild conditions. The anchored Cu(II) could not leach out from the surface of the mesoporous catalyst during the reaction and it has been reused several times without appreciable loss in its catalytic activity.     

Synthesis and characterization of chiral benzylic ether-bridged periodic mesoporous organosilicas

The first synthesis of a chiral periodic mesoporous organosilica (PMO) carrying benzylic ether bridging groups is reported. By hydrolysis and condensation of the new designed chiral organosilica precursor 1,4-bis(triethoxysilyl)-2-(1-methoxyethyl)benzene (BTEMEB) in the presence of the non-ionic oligomeric surfactant Brij 76 as supramolecular structure-directing agent under acidic conditions, an ordered mesoporous chiral benzylic ether-bridged hybrid material with a high specific surface area was obtained. The chiral PMO precursor was synthesized in a four-step reaction from 1,4-dibromobenzene as the starting compound. The evidence for the presence of the chiral units in the organosilica precursor as well as inside the PMO material is provided by optical activity measurements.     

Unexpected golden Ullmann reaction catalyzed by Au nanoparticles supported on periodic mesoporous organosilica (PMO)

We demonstrated an unprecedented example of Ullmann homocoupling reaction of aryl iodides over a novel recyclable gold catalyst comprising Au nanoparticles supported on a bifunctional periodic mesoporous organosilica (Au@PMO).     

苯官能化MCM-41的合成、表征、磺酰化及与二胺的反应

以三乙氧基硅基苯((C₂H₅O)₃Si-Ph，（(triethoxysilyl)benzene，TESB)以及正硅酸乙酯（TEOS）的混合液为硅源，以溴代十六烷基吡啶(CPBr)为模板剂，在HCl介质中合成了苯官能化的有机-无机杂化介孔分子筛MCM-41。对合成的分子筛用FT-IR、PXRD、TEM、N₂吸附-脱附等手段进行了表征。结果表明，合成的苯官能化的有机-无机杂化介孔分子筛具有良好的介孔孔道结构。用三甲基氯硅烷对分子筛表面的Si-OH进行了封端处理，用氯磺酸对合成的苯官能化的有机-无机杂化介孔分子筛进行了磺酰化，并与各种二胺进行了反应。     

周期有序介孔Rh(Ⅰ)有机金属催化剂用于水介质Heck反应的研究

以1,4-双(三乙氧基硅基)苯和2-(二苯基膦)乙基三乙氧基硅烷为混合硅源, 在表面活性剂作用下共缩聚得到二苯基膦功能化的有序介孔有机硅材料[PPh₂-PMO(Ph)], 通过配位作用将Rh(Ⅰ)有机金属催化剂固载到PPh₂-PMO上得到Rh(Ⅰ)-PPh₂-PMO(Ph)非均相催化剂, 并采用FTIR, NMR, XRD, TEM和氮气吸附等手段对催化剂进行了表征. 考察了该催化剂在水介质Heck反应中的催化性能, 实验结果表明, 所制备的Rh(Ⅰ)-PPh₂-PMO(Ph)具有与均相催化剂Rh(PPh₃)₃Cl相当的催化活性, 这主要归因于催化剂的高比表面积、有序介孔结构有利于提高Rh(Ⅰ)活性位的分散度, 减少了传质阻力; 同时PMO构建形成的微环境增强了表面疏水性, 有利于反应底物的吸附和扩散. 此外, 催化剂重复使用多次后活性仍没有明显降低.     

Highly efficient three-component coupling reaction catalyzed by gold nanoparticles supported on periodic mesoporous organosilica with ionic liquid framework

A novel gold nanoparticle supported periodic mesoporous organosilica with alkylimidazolium framework, Au@PMO-IL, was shown to be a highly active and recyclable catalyst for three-component coupling reaction of aldehyde, alkyne and amine to give the corresponding propargylamine.     

Organorhodium‐Functionalized Periodic Mesoporous Organosilica: High Hydrophobicity Promotes Asymmetric Transfer Hydrogenation in Aqueous Medium

Three organosilica‐bridged periodic mesoporous organosilicas were prepared by the immobilization of a chiral N‐sulfonylated diamine‐based organorhodium complex within their silicate network. Structural analysis and characterization confirmed their well‐defined single‐site active rhodium centers, whilst electron microscopy revealed their highly ordered hexagonal mesostructures. Among these three different organosilica‐bridged periodic mesoporous organosilicas, the ethylene‐bridged periodic mesoporous organosilica catalyst exhibited excellent heterogeneous catalytic activity and high enantioselectivity in the aqueous asymmetric transfer hydrogenation of aromatic ketones. This superior catalytic performance was attributed to its salient hydrophobicity, whilst its comparable enantioselectivity relative to the homogeneous catalyst was derived from the confined nature of the chiral organorhodium catalytic sites. Furthermore, this ethylene‐bridged periodic mesoporous organosilica could be conveniently recovered and reused at least 12 times without the loss of its catalytic activity. This feature makes this catalyst attractive for practical organic synthesis in an environmentally friendly manner. This study offers a general way of optimizing the bridged organosilica moiety in periodic mesoporous organosilicas, thereby enhancing its catalytic activity in heterogeneous catalysis.     

Selective oxidation of alcohols with hydrogen peroxide catalyzed by tungstate ions (WO4) supported on periodic mesoporous organosilica with imidazolium frameworks (PMO-IL)

Tungstate ions supported on the periodic mesoporous organosilica with ionic liquid frameworks (WO₄⁼@PMO-IL) were found to be a recoverable catalyst system for the highly selective oxidation of various primary or secondary alcohols to the corresponding aldehydes or ketones by 30% H₂O₂ as green oxidant under neutral aqueous reaction conditions. The catalyst can be also recovered and efficiently reused in seven subsequent reaction cycles without any remarkable decreasing in the catalyst activity and selectivity. Moreover, N₂ sorption analysis, transmission electron microscopy (TEM) images, and thermal gravimetric analysis (TGA) showed that the structure regularity and functional groups loaded of the catalyst were not affected during the reaction process.     

Functionalized Periodic Mesoporous Organosilica: A Highly Enantioselective Catalyst for the Michael Addition of 1,3‐Dicarbonyl Compounds to Nitroalkenes

A functionalized periodic mesoporous organosilica with incorporated chiral bis(cyclohexyldiamine)‐based Ni^II complexes within the silica framework was developed by the co‐condensation of (1R,2R)‐cyclohexyldiamine‐derived silane and ethylene‐bridge silane, followed by the complexation of NiBr₂ in the presence of (1R,2R)‐N,N′‐dibenzylcyclohexyldiamine. Structural characterization by XRD, nitrogen sorption, and TEM disclosed its orderly mesostructure, and FTIR and solid‐state NMR spectroscopy demonstrated the incorporation of well‐defined single‐site bis(cyclohexyldiamine)‐based Ni^II active centers within periodic mesoporous organosilica. As a chiral heterogeneous catalyst, this functionalized periodic mesoporous organosilica showed high catalytic activity and excellent enantioselectivity in the asymmetric Michael addition of 1,3‐dicarbonyl compounds to nitroalkenes, comparable to those with homogeneous catalysts. In particular, this heterogeneous catalyst could be recovered easily and reused repeatedly up to nine times without obviously affecting its enantioselectivity, thus showing good potential for industrial applications.     

Pd/PMO-SBA-15 催化剂催化苯甲醇选择氧化反应性能

 研究了 PMO-SBA-15 材料负载的金属钯纳米粒子 (Pd/PMO-SBA-15) 在水相中催化苯甲醇选择氧化制苯甲醛的反应. 考察了纳米粒子种类、氧化剂用量、反应时间和反应温度等对苯甲醇转化率及苯甲醛选择性的影响. 结果表明, 以水为溶剂, 以 H2O2 (30%) 为氧化剂时, 可得到较高的苯甲醇转化率和苯甲醛选择性. 当以 0.05 g 的 2%Pd/PMO-SBA-15 为催化剂, H2O2 用量为 1.5 ml, 反应温度为 80 oC, 反应 4 h 时, 苯甲醇转化率和苯甲醛选择性分别达到 97.1% 和 100.0%. 对该催化体系的重复使用性能进行了考察. 结果发现, 随着使用次数的增加, 苯甲醇转化率有所下降, 但苯甲醛选择性保持不变.     

手性Ru复合物催化剂的固载化及其不对称氢转移反应催化应用

Chiral Ru-BsDPEN, (1R,2R)-N-p-benzenesulfonyl-1,2-diphenylethylenediamine, catalyst has been immobilized on a mesoporous molecular sieve of MCM-41 type successfully. A hybrid mesoporous molecular sieve was synthesized using a precursor bearing benzene group, which in organosilica were sulfonylated and reacted with (1R,2R)-l,2-diphenylethylenediamine and [RuC1E(p-cymene)]2 successively to afford immobilized catalyst. The Brunauer-Emmett-Teller (BET) surface area and Barrett-Joyner-Halenda (BJH) pore size decreased after immobilization of catalyst onto the mesoporous material. Enantioselective transfer hydrogenation of ketones catalyzed by immobilized catalyst showed the highest yield of 22.36% and e.e. value of 31.47% by using acetophenone as substrate when reaction time was 48 and 16 h respectively.     

乙基桥联有序介孔有机硅负载Pd(Ⅱ)有机金属催化剂用于水介质Barbier反应

以PPh2C2H4-Si(OEt)3和(EtO)3Si-C2H4-Si(OEt)3为混合硅源,在表面活性剂作用下共缩聚制备有序介孔有机硅杂化材料,再络合Pd(Ⅱ)离子得到固载化Pd(Ⅱ)非均相催化剂.在水介质Barbier反应中,所制备的Pd(Ⅱ)-PPh2-PMO(Et)具有与均相Pd(PPh3)2Cl2催化剂相当的催化活性,主要归因于高比表面积、有序介孔结构,有利于提高Pd(Ⅱ)活性位分散度,减少传质阻力,同时乙基修饰孔壁增强表面疏水性,有利于有机分子在孔道内的扩散和活性位上的吸附,导致高催化活性,而且可重复使用,显示了良好的工业应用前景.     

Manganese‐Containing Periodic Mesoporous Organosilica with Ionic‐Liquid Framework (Mn@PMO‐IL): A Powerful,Durable, and Reusable Nanocatalyst for the Biginelli Reaction

The catalytic application of a novel manganese‐containing periodic mesoporous organosilica with ionic‐liquid framework (Mn@PMO‐IL) in the Biginelli reaction was investigated. First, the Mn@PMO‐IL nanocatalyst was prepared and characterized by TEM, SEM, X‐ray photoelectron spectroscopy, and nitrogen‐sorption analysis. The catalyst was then used in the one‐pot Biginelli condensation of various aldehydes with urea and alkyl acetoacetates under solvent‐free conditions. The corresponding dihydropyrimidone products were obtained in high to excellent yields and selectivities at short reaction times. Moreover, the catalyst was recovered and successfully reused many times with no notable decrease in activity and selectivity.     

Crystal-like periodic mesoporous organosilica bearing pyridine units within the framework

Periodic mesoporous organosilica with densely packed pyridine units within the framework and crystal-like molecular-scale periodicity was synthesized. The framework pyridines were chemically active and fully accessible for protonation and Cu(2+) adsorption.     

An alternate route for the synthesis of hybrid mesoporous organosilica with crystal-like pore walls from allylorganosilane precursors

The bridged allylorganosilanes 1,4-bis(diallylethoxysilyl)benzene and 1,4-bis(triallylsilyl)benzene are presented as new precursors for the surfactant-assisted synthesis of ordered mesoporous organosilica with pore walls having crystal-like molecular-scale periodicity. This approach provides a new route to the formation of periodic mesostructures with crystal-like pore walls. The synthesis method presented is applicable to the preparation of mesoporous organosilica with bulky organic groups, the precursors of which are typically impossible to obtain in high purity.     

Ordered Mesoporous Organosilica with Ionic‐Liquid Framework: An Efficient and Reusable Support for the Palladium‐Catalyzed Suzuki–Miyaura Coupling Reaction in Water

The preparation of a novel palladium‐supported periodic mesoporous organosilica based on alkylimidazolium ionic liquid (Pd@PMO‐IL) in which imidazoilium ionic liquid is uniformly distributed in the silica mesoporous framework is described. Both Pd@PMO‐IL and the parent PMO‐IL were characterized by N₂‐adsorption–desorption, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), TEM, and solid‐state NMR spectroscopy. We have demonstrated that Pd@PMO‐IL is an efficient and reusable catalyst for the Suzuki–Miyaura coupling reaction of various types of iodo‐, bromo‐, and even deactivated aryl chlorides in water. It was also found that although the PMO‐IL nanostructure acts as reservoir for soluble Pd species, it can also operate as a nanoscaffold to recapture the Pd nanoparticles into the mesochannels thus preventing extensive agglomeration of Pd. This observation might be attributed to the isolated ionic liquid units that effectively control the reaction mechanism by preventing Pd agglomeration and releasing and recapturing Pd nanoparticles during the reaction process. The catalyst can be recovered and reused for at least four reaction cycles without significant loss of activity.     

有序介孔炭负载铜基催化剂Cu/CMK-3用于气相甲醇氧化羰基化反应

通过纳米浇铸法合成了有序介孔炭CMK-3,再通过浸渍法制备了Cu/CMK-3催化剂,并将其用于气相甲醇氧化羰基化反应。N2吸附-脱附测试、X射线衍射(XRD)以及透射电镜(TEM)的表征结果表明,Cu/CMK-3具有序介孔结构,活性Cu物种均匀分散于CMK-3的表面及孔道中,粒径为10~20 nm,远小于相同条件下制备的铜/活性炭(Cu/AC)催化剂。固定床反应器的活性评价结果显示450℃下制备的Cu/CMK-3催化活性最高,反应10 h内碳酸二甲酯(DMC)的时空收率(STY)达到286 mg·g^-1·h^-1,选择性为76%。长周期活性评价结果表明Cu/CMK-3稳定性较相同条件下制备的Cu/AC有大幅提高,50 h内DMC的STY降低了20%,75 h内降低了28%。     

Synthesis and characterization of MgO nanoparticles supported on ionic liquid‐based periodic mesoporous organosilica (MgO@PMO‐IL) as a highly efficient and reusable nanocatalyst for the synthesis of novel spirooxindole‐furan derivatives

The synthesis and catalytic application of a novel MgO containing periodic mesoporous organosilica with ionic liquid framework (MgO@PMO‐IL) is described. The prepared MgO@PMO‐IL was characterized by Fourier transform‐infrared spectroscopy, N₂ adsorption/desorption, transmission electron microscopy, field emission‐scanning electron microscopy, thermogravimetric and inductively coupled plasma analyses. This nanocatalyst was successfully applied as a highly efficient and recoverable catalyst for the synthesis of novel spirooxindole‐furan derivatives via the three‐component reaction of 1,3‐dicarbonyl compounds, N‐phenacyl pyridinium salts and isatin derivatives. The products were achieved in high to excellent yields with a simple work‐up procedure and short reaction times, and the catalyst could be recovered through a simple filtration process and successfully reused seven times without any significant decrease in its efficiency.     

Palladium containing periodic mesoporous organosilica with imidazolium framework (Pd@PMO-IL): an efficient and recyclable catalyst for the aerobic oxidation of alcohols

The application of a novel palladium containing ionic liquid based periodic mesoporous organosilica (Pd@PMO-IL) catalyst in the aerobic oxidation of primary and secondary alcohols under molecular oxygen and air atmospheres is investigated. It was found that the catalyst is quite effective for the selective oxidation of several activated and non-activated alcoholic substrates. The catalyst system could be successfully recovered and reused several times without any significant decrease in activity and selectivity. Moreover, the hot filtration test, atomic absorption spectroscopy (AA) and kinetic study with and without selective catalyst poisons showed that the catalyst works in a heterogeneous pathway without any palladium leaching in reaction solution. Furthermore, nitrogen-sorption experiment and transmission electron microscopy (TEM) image proved the superior stability of high-ordered PMO-IL mesostructure during reaction process. TEM image also confirmed the presence of well-distributed Pd-nanoparticles in the uniform mesochannels of the material. These observations can be attributed to the ionic liquid nature of PMO-IL mesostructure which facilitates the reaction through production, chemical immobilization and stabilization of active palladium nanoparticles, as well as preventing Pd-agglomeration during overall process.     

Heterogeneous organocatalysis at work: functionalization of hollow periodic mesoporous organosilica spheres with MacMillan catalyst

We report a new method for the synthesis of hollow-structured phenylene-bridged periodic mesoporous organosilica (PMO) spheres with a uniform particle size of 100-200 nm using α-Fe(2)O(3) as a hard template. Based on this method, the hollow-structured phenylene PMO could be easily functionalized with MacMillan catalyst (H-PhPMO-Mac) by a co-condensation process and a "click chemistry" post-modification. The synthesized H-PhPMO-Mac catalyst has been found to exhibit high catalytic activity (98% yield, 81% enantiomeric excess (ee) for endo and 81% ee for exo) in asymmetric Diels-Alder reactions with water as solvent. The catalyst could be reused for at least seven runs without a significant loss of catalytic activity. Our results have also indicated that hollow-structured PMO spheres exhibit higher catalytic efficiency than solid (non-hollow) PMO spheres, and that catalysts prepared by the co-condensation process and "click chemistry" post-modification exhibit higher catalytic efficiency than those prepared by a grafting method.