NH2-MOFs固载离子液体催化剂的构建及CO2 环加成反应催化性质研究

CO2和环氧化物反应合成环状碳酸酯是CO2化学利用的重要途径。传统以硅基材料或高分子聚合物为载体制备的固载化离子液体催化剂缺乏对CO2的吸附活化中心，造成反应压力较高，反应速率较慢。针对这一问题，本项目提出设计合成一种新型酸-碱双功能固载化离子液体催化剂：以具有强CO2吸附能力的介孔NH2-Cr-MIL-101为载体，以其配位不饱和金属位点固载离子液体，通过酸-碱协同作用催化环加成反应。重点研究离子液体固载化方法和条件对催化剂的结构稳定性及表面酸-碱性的影响；考察离子液体组成和性质对环氧化物吸附活化能力的影响，建立环氧化物和CO2的吸附活化模型；研究离子液体烷基碳链长度对酸-碱中心的纳米尺度及协同催化作用的影响，揭示载体孔道织构性质在反应过程中的扩散-限域作用；探讨反应机理。本项目的开展为开拓温和条件下CO2和环氧化物环加成反应催化剂、实现CO2资源化利用具有重要意义。

The process of cyclic carbonates synthesis from CO2 and epoxides is an important route toward CO2 utilization. Immobilized ionic liquids catalysts using silica-based and polymers as supports lack adsorption and activation centers for CO2 resulting in high reaction pressure and low reaction rate. In this respect, a novel type of acid-base bi-functional catalyst, immobilized ionic liquids, is proposed in this research project. Specifically, the mesoporous NH2-Cr-MIL-101 with excellent capacity of CO2 adsorption as support, wherein the coordinatively unsaturated metal sites (CUSs) are used to immobilize ionic liquids. The resulting acid-base cooperativity is constructed to catalyze cycloaddition of CO2 to epoxides. The effect of immobilization methods on stability and acidic-basic property of catalyst will be systematically investigated. Meanwhile, the influence of composition and property of ionic liquids on adsorption and activation of epoxide will be discussed. On the basis of the above results, the model toward CO2 adsorption and activation is proposed. Furthermore, the effect of length of alkyl chain on nanoscale of acid-base centers and the cooperative mechanism will be studied. The aim is to reveal the role of support in diffusion and confinement effect of catalyst and discuss the reaction mechanism. This research project paves the way to design and develop an efficient catalyst for the synthesis of cyclic carbonates from CO2 and epoxides under mild condition, as well as is promising for conversion and utilization of CO2.