功能化离子液体阳离子和阴离子协同调控的金属纳米颗粒：催化加氢和温控分离

The highly efficient reaction and clean separation are attractive topics not only in catalytic fundamental research but also in chemical industry. In this project, the new ionic liquids consisted of poly(ethylene glycol) (PEG)-functionalized imidazolium cation and alkyl-bis(m-sulfonated-phenyl)- phosphine anioins, have been constructed and were employed as stabilizing agents for different metal nanoparticles (Pd, Ru and Rh etc). The ionic liquid-modulating nanocatalysts will be characterized by Fourier Transform Infrared Spectroscopy (FT-IR), Nuclear Magnetic Resonance (NMR), High Resolution Transmission Electron Microscopy (HRTEM), X-ray Diffraction(XRD), X-ray Photoelectron Spectroscopy (XPS), Thermal Gravimetric Analysis (TGA), Dynamic Light Scattering (DLS) and Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) etc. On the basis of the characterization above, the nanocatalysts are utilized for selective hydrogenation of linear olefins, cyclo-olefins, alpha,beta-unsaturated aldehyde (esters, ketones, alcohols, acids) and asymmetric hydrogenation in low-toxic reaction media like ethyl acetate under very mild reaction condition. The project aimed to design and prepare size and shape-controlling, as well as thermoregulated phase-separable nanocatalyst system. Through the investigations related to this project,the scientific principles governing thermoregulated phase-separable catalysis should be understood with a series of thermoregulated ionic liquids; the the cooperative roles between the cation and anion of the functionalized ionic liquids in immobilizing and modifying metal nanoparticles can be realized in depth. Simultaneously, the approach of manipulating the size, morphology and surface properties of nano-scale metal particles is established, and also the mechanism influencing the activity and selectivity of catalytic hydrogenation is revealed. Finally, the highly efficient reaction and thermoregulated phase separation are attained with the functionalized ionic liquid-regulated nano-catalyst system. In summary, the research related to this project can offer an insight into the thermoregulated and catalytic behavior of ionic liquid-manipulating metal nanoparticles, and also opens new approach towards a facile, rational strategy to modify the properties of nanocatalysts with optimized catalytic performance.

拓展高效反应-清洁分离的催化反应体系具有重要的应用价值，值得进一步深入研究。本项目以聚乙二醇链（PEG）功能化的咪唑阳离子、烷基-二（间-苯基磺酸）膦阴离子组合而构筑新型功能化离子液体，并以此为金属纳米颗粒的稳定剂，设计和制备离子液体调控的金属纳米催化剂体系, 目的在于实现均相反应-温控分离的目标。首先通过各种手段表征，阐明功能化离子液体稳定的纳米催化剂的重要功能，利用不同体积、供电子能力的配体阴离子，建立调控纳米颗粒尺度、形貌以及表面性质的方法，认识金属纳米颗粒性质影响加氢活性、（手性）选择性的规律，同时理解聚乙二醇链功能化的咪唑阳离子产生温控效应的机制，阐明离子液体阴、阳离子在对纳米催化剂协同调控作用。项目研究成果对于揭示决定纳米颗粒催化加氢活性、（手性）选择性的主要因素、温控分离性能具有重要的科学意义，为拓展此类体系在催化领域内的新应用提供可借鉴的思路和方法。

手性仲醇在医药、农药及香精香料等精细化工方面有着十分广泛的应用，通过不对称催化加氢途径，由前手性酮加氢是得到手性仲醇最重要方法之一，所使用的催化剂主要是以手性胺和膦配体稳定的Ru配合物的均相催化剂，其对加氢反应呈现优良的活性和对映选择性，但贵金属催化剂和产物的分离一直是亟待解决的难题。本课题主要目标是设计阴、阳离子功能化的离子液体，并以此为金属纳米颗粒/配合物的稳定剂和修饰剂，设计具有手性加氢性能的金属催化剂体系, 一方面实现对前手性酮的不对称加氢，得到重要的手性醇，同时利用离子液体催化剂的温敏特征，实现反应温度下均相加氢，反应完成降至室温后催化剂进行多相分离，为智能催化剂(Smart catalyst)的设计提供可参考的依据。本项目主要设计并制备了一系列新型功能化温控离子液体，并筛选出的特殊结构的阳离子实现对金属纳米/配合物催化剂的温控分离，而得到的阴离子则提供催化加氢的活性中心，设计的离子液体催化剂在温和的反应条件下（20-50oC，1.0 MPa），对一系列芳香酮的衍生物具有良好的转化活性（转化率大于97%），手性选择性大于98%，反应后催化剂经过温控分离可循环使用至少6次，活性和手性选择性均保持不变，同时贵金属流失量小于10 ppm。研究结果表明设计的离子液体阴、阳离子对金属催化剂起协同调控作用，离子液体-金属配合物的结构显著影响其温控分离性能，活性和手性选择性，本项目设计的手性加氢反应体系不需要常规繁琐的分离方法，温控分离操作简单、快捷，这对于昂贵的手性加氢的贵催化剂尤为重要，此温控分离的催化剂体系可以方便拓展应用到其它贵金属催化的反应体系中，具有很广泛应用前景。