二氧化碳（CO2）和环氧丙烷（PO）反应合成环状碳酸酯是CO2固定的主要途径之一，为这个反应寻找合适的催化剂是一个备受关注的问题。离子液体可以在较温和的条件下催化该反应，是一种高效、绿色的催化剂。以往的研究主要集中在惰性化离子液体上，而质子化离子液体受到的关注相对较少，绝大多数质子化离子液体催化CO2固定反应的活性和机理还不清楚。本项目拟采用理论计算和实验相结合的方法，系统地研究：（1）质子化离子液体催化CO2固定反应的反应机理，重点确定质子化离子液体的氢键网络在催化过程中扮演的角色；（2）在质子化离子液体上引入官能团，得到功能化离子液体，用理论方法预测其催化活性；（3）由氢键网络的差异所导致的功能化与非功能化离子液体催化活性和催化机理的差异；（4）实验合成与验证。通过本项目的实施，为实现从分子水平上设计质子化离子液体催化剂奠定理论基础。

The coupling reaction of epoxide (PO) with carbon dioxide (CO2) to afford the five-membered cyclic carbonates is one of the most significant approaches for the chemical fixation of CO2. Due to the thermodynamic stability and kinetic inertness of CO2, the catalyst is an essential factor to complete this process. The exploration of the suitable catalysts has attracted considerable attentions. Ionic liquid is one class of high-efficiency and “green” catalysts, which could catalyze the CO2 fixation in the benign condition. In the past decades, lots of studies have been performed on the non-protic ionic liquids. In contrast, few attentions have been focused on the protic ionic liquids. Their catalytic activity and mechanism are still ambiguous and worthy of further exploration. The goals of this project are to explore the detailed mechanism of CO2 with PO catalyzed by protic ionic liquid; in particular to determine the role of hydrogen bond network played in catalytic cycle; furthermore to design the task-specified protic ionic liquids and compare their catalytic activity with the non-protic ionic liquids. Finally, the newly designed ionic liquids with better catalytic activity will be synthesized and their reactivity will be tested by experiments. We hope that the abovementioned work would provide valuable theoretical clues for the design of protic ionic liquids from the molecular level.