CO_(2)加氢制甲酸理论研究及高效铁基催化剂设计北大核心CSCD

CO_(2)加氢制甲酸由于需同时活化惰性氢气及CO_(2)而富有挑战性,同时此过程原子经济性100%,具有很好的理论和现实研究价值,但文献中报道的活性较好的催化剂均为贵金属催化剂.为了开发活性更高的用于CO_(2)加氢制甲酸的铁基催化剂,我们采用理论计算方法研究了12种不同种类的PNP-Fe(PNP=2,6-(二-叔丁基-磷甲基)吡啶)化合物催化CO_(2)加氢制甲酸的过程.理论研究结果表明,CO_(2)加氢制甲酸反应过程包括H2活化及CO_(2)插入金属氢键两个步骤,H_(2)活化过程是整个反应的速控步骤.催化剂吡啶环上进行P原子取代可以显著降低H_(2)活化能垒.基于以上发现,我们设计了一种新颖的高效铁基催化剂,使用此催化剂催化CO_(2)加氢制甲酸反应,速控步骤能垒只有85.6 kJ/mol,催化活性与贵金属的比较接近.我们研究的12种铁基催化剂速控步骤能垒范围为85.6~126.4 kJ/mol,显示了配体良好的调控催化活性能力.

Theoretical Calculation on the CO2 Hydrogenation to Formic Acid and Design More Effective Iron Based Catalyst for this Process

CO2 hydrogenation is full of challenge because both H2 and CO2 are activated at the same time. This reaction also has 100% atomic economy. Most of the reported catalysts for CO2 hydrogenation are based on noble metal. To find out more effective iron based catalysts for the CO2 hydrogenation to formic acid, totally, the reaction processes catalyzed by 12 different PNP-Fe (PNP=2,6-bis(di-tert-butylphosphinomethyl)pyridine) compounds were investigated. The theoretic calculation results revealed that the CO2 hydrogenation included two steps: H2 activation and CO2 inserting into the metal-hydride bond. The H2 activation is the rate-determining step. It was found that P atom substitution on the pyridine ring could obviously reduce the H2 activation barrier. Based on these findings, an effective Fe catalyst was designed, whose H2 activation barrier was only 85.6 kJ/mol, being comparable to the data of precious metal catalyst. The H2 activation barriers range from 85.6 to 126.4 kJ/mol for different Fe-based catalysts investigated here, indicating that the modification of ligand has great influence on the catalytic reactivity for the CO2 hydrogenation.