面向温和条件下二氧化碳转化为含氧化合物设计合成功能化多孔超交联离子聚合物高效催化剂

Efficient conversion of CO2 into oxygenated compounds can promote the application of abundant CO2 as C1 resource and reduce the emission of greenhouse gases. The challenge comes from the designation of high-performance heterogeneous catalysts under mild condition. Based on the applicant’s long-term research and obtained results about the mesoporous poly(ionic liquid)s and CO2 adsorption/conversion, this project propose to design novel multifunctional porous hypercrosslinked ionic polymers (PHIPs) as heterogeneous catalysts for the cycloaddition of CO2 into cyclic carbonates under mild condition (down to ambient condition) by using no solvent and additive. PHIPs were thus used to fabricate the green efficient heterogeneous catalytic coupling process for the direct transformation of CO2 into other high value-added organic chemicals such as dimethyl carbonate and oxazolidinones. Two synthetic routes were adopted: 1) direct hypercrosslinking process through Friedel-Crafts alkylation reaction; 2) the combination of two successive steps of free radical copolymerization and post-hypercrosslinking procedure. The functional groups were incorporated in the ionic liquid unit or introduced by adding functional organic compounds in the hypercrosslinking process. The synthetic conditions were adjusted to control the co-hypercrosslinking rate of ionic liquid monomer and external crosslinker, aiming to achieve PHIPs with large surface area, high content of ionic liquid unit and versatile functional groups. The structure-performance relationship was investigated to gain insight into the synergistic effect of the porosity, ionic sites and functional groups on the CO2 conversion. This study will provide a new route and scientific foundation to establish the green heterogeneous catalytic process for highly effective chemical conversion of CO2.

将CO2高效地转化为含氧化合物，既能利用丰富的CO2作为C1资源，又能减少温室气体的排放。然而设计温和反应条件下的高效多相催化剂一直是个挑战。基于申请人在介孔聚离子液体和CO2吸附转化领域的研究积累和进展，本项目提出设计基于超交联聚合物的功能化多孔离子框架，旨在实现在温和条件下（如无溶剂、无助剂，低至常温常压）将CO2高效转化为环状碳酸酯，并以此构建一锅法合成碳酸二甲酯及噁唑啉酮等含氧化合物的绿色高效多相催化耦合过程。拟采用一步超交联和先共聚后超交联两种合成路径，通过设计功能化离子液体或者加入功能化有机分子，优化合成条件，控制离子液体与外交联剂的竞聚率，构筑组成、结构可调的功能化多孔超交联离子聚合物，特征在于具有大的比表面积、高的离子液体含量、功能多样的官能团。深入研究孔道、离子液体单元、功能化基团协同催化CO2转化的作用机制，为构建绿色高效CO2转化的多相催化工艺提供新途径和科学基础。

二氧化碳是典型的温室气体，同时又是一种储量丰富、潜力巨大的绿色可再生碳资源。将二氧化碳转化为高附加值的化学品，能减少温室气体的排放以及对化石资源的依赖，促进二氧化碳的资源化利用。本项目围绕超交联离子型聚合物等离子液体多相催化剂的制备以及它们在二氧化碳转化中的应用开展了一系列工作。通过单体设计、交联方式筛选、合成条件优化，制备了微孔超交联离子聚合物、介孔离子均聚物/共聚物、有序离子型共价有机框架和负载线性聚离子液体的有序介孔碳材料等功能化离子型聚合物催化剂。系统考察了单体结构、交联方式、聚合条件（单体比例、溶剂、引发剂、温度和时间等）等对离子聚合物中化学组成和孔道结构的影响，揭示了系列离子聚合物结构调控规律，构筑了系列具有可调离子中心、高比表面积、高离子液体含量和丰富官能团的离子聚合物催化剂。将这些离子聚合物催化剂应用于二氧化碳与一系列环氧化物和氮杂环化物的环加成反应中，全面系统地评价了催化剂的活性和稳定性，研究了孔道结构、化学组成以及表面官能团等对催化性能的影响。结合催化活性评价和密度泛函模拟计算，深入探讨了催化机理，初步阐释了离子聚合物中离子液体种类/含量、孔道结构、表面官能团协同催化二氧化碳与环氧化物、氮杂环化物环加成反应的规律。获得系列高效的离子聚合物催化剂，形成了系列在温和条件下（低至常温常压）将二氧化碳转化为环状碳酸酯、碳酸二甲酯和噁唑啉酮等高附加值含氧化合物的新工艺。这些研究成果为离子液体的异相化和多孔化，构筑新型多孔聚合物催化剂提供了新的思路，为二氧化碳高效转化设计绿色高效催化剂提供了新的途径和科学依据。