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降低CO2功能的N-异环碳素的真正作用:密度功能理论研究的替代理解
1State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, P. R. China.
Journal of the American Chemical Society
|July 30, 2015
概括
N-异环碳素 (NHC) 作为离子液体催化剂的前体,使CO2具有高效的还原功能. 新的S(N) 2@Si受体机制降低了二氧化碳转化为甲胺或甲醇的能量障碍.
科学领域:
- 有机金属化学
- 催化剂
- 计算化学
背景情况:
- N-异环碳酸 (NHC) 是多用途的配体和有机催化剂.
- 二氧化碳 (CO2) 的降低功能对于可持续化学至关重要.
- 了解催化机制是设计高效催化剂的关键.
研究的目的:
- 综合研究由NHC催化形式化二氧化碳的机制.
- 发现NHC催化二氧化碳转换的新低能量激活途径.
- 阐明NHC作为前体和直接催化剂的作用.
主要方法:
- 用密度函数理论 (DFT) 的计算来研究反应途径.
- 对过渡状态和中间体进行分析,以确定能源障碍.
- 在氨基酸的存在和缺席下对二氧化碳转换的催化循环的探索.
主要成果:
- 发现了一种新型的激活模式,称为"S(N) 2@Si-接受器",具有明显较低的能量障碍.
- NHC 作为前体,形成现场离子液体 ([NHCH](+) [碳酸盐](-)) 或作为活性催化剂的 NHC-CO2 添加物.
- 活性部位转移到碳酸盐或二氧化碳添加物的负电荷氧原子,促进核友性攻击和化物转移.
结论:
- 发现的离子液体和NHC-CO2 adduct路径为CO2功能化提供了更稳定的热力学和更有利的动力学路径.
- 这些机制克服了与传统NHC催化相关的固体限制.
- 这些发现为NHC介导的二氧化碳转化提供了新的见解,为更高效的催化系统铺平了道路.
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