TBAI辅助三嗪聚合物催化CO_(2)与环氧氯丙烷环加成反应机理的理论研究  

Theoretical study on the mechanism of the cycloaddition reaction of CO2 and epichlorohydrin catalyzed by a triazine-based polymer with TBAI co-catalyst

作　　者：魏卓 钟欣欣[1] 张干兵[1] WEI Zhuo;ZHONG Xinxin;ZHANG Ganbing(College of Chemistry and Chemical Engineering,Hubei University,Wuhan 430062,Hubei,China)

机构地区：[1]湖北大学化学化工学院,湖北武汉430062

出　　处：《化学研究》2024年第4期321-327,共7页Chemical Research

基　　金：国家自然科学基金(21675058,21671061)。

摘　　要：二氧化碳排放量的增加对环境造成了重大威胁。利用含氮和卤素的有机催化剂可以催化CO_(2)与环氧化物的环加成反应。用ωB97X-D/def2-TZVP//ωB97X-D/def2-SVP方法,结合SMD溶剂化模型,计算了三嗪骨架聚合物催化剂与四丁基碘化铵(TBAI)助催化剂的复合催化体系(Cat-I)催化CO_(2)与环氧氯丙烷(ECH)加成为环碳酸酯的详细反应机理。计算结果显示,在Cat-I的催化作用下,ECH先活化的路径为最低能量路径。亚胺基氢键供体活化ECH中的C-O键,I-的强亲核性和离去能力协同作用促进反应的进行。其决速中间体(TDI)为起始反应物,决速过渡态(TDTS)为碳酸半酯的闭环步骤的过渡态,表观自由能垒为33.54 kcal/mol,比无助催化剂时的能垒低16.55 kcal/mol。这与105℃、常压下、TBAI为助催化剂时三嗪骨架聚合物催化目标反应的转化率为100%,而无助催化剂时转化率仅为70%的实验事实相符。The increase in CO2 emissions poses a major threat to the environment.The cycloaddition reaction of CO2 and epoxides can be catalyzed using nitrogen-and halogen-containing organocatalysts.The detailed reaction mechanism of the addition of CO2 and epichlorohydrin(ECH)to cyclic carbonate catalyzed by a composite catalytic system(Cat-I)of a triazine-based polymer catalyst and a tetrabutylammonium iodide(TBAI)co-catalyst has been calculated using theωB97XD/def2-TZVP//ωB97XD/def2-SVP method in conjunction with the SMD solvation model.Calculated results show that the ECH-first-activation path is the lowest energy path for the target reaction with the catalysis of Cat-I.In the catalytic process with Cat-I,the C-O bonds in ECH are activated by the hydrogen-bond donor of the imidogen group,and the synergistic effects of strong nucleophilicity and dissociative ability of I-promote the reaction.The turnover frequency(TOF)-determining intermediate(TDI)is the starting reactants,and the TOF-determining transition state(TDTS)is the transition state of the step of the cyclization of the carbonic hemiester.The apparent free energy barrier for the catalysis of Cat-I is 33.54 kcal/mol,being 16.55 kcal/mol lower than that for Cat without co-catalyst.Which are in line with the experimental observation of the 100%and 70%conversions for the reaction in the conditions of 1.02 atm pressure and 105℃,catalyzed by the triazine-based polymer catalyst with or without TBAI co-catalyst,respectively.

关 键 词：密度泛函理论 CO_(2)转化 有机催化剂 决速态 

分 类 号：O643[理学—物理化学]