A Polar Structure-Induced Electronic Tunneling Strategy Leveraging FLP-ILs Synergistically Enhances the Hydrogen Activation.

The excessive emission of carbon dioxide has garnered significant global attention, prompting extensive research into its capture, sequestration, and conversion. Among these strategies, carbon dioxide conversion is pivotal to its reuse. Given the cleanliness and efficiency of hydrogen energy, the hydrogenation of carbon dioxide has emerged as a focal point of interest, with hydrogen activation serving as a crucial step in the conversion of CO2. To further enhance the activity of hydrogen, a seriously frustrated Lewis pair-ionic liquids (FLP-ILs) catalytic system has been proposed and applied in hydrogen activation. It is noteworthy that the distinct structures of ILs and FLPs give rise to variations in their hydrogen activation effects. Based on DFT calculations, we conducted a study on the effects of a series of intermolecular and intramolecular FLP and imidazolium-based ILs composite systems on hydrogen activation. Additionally, a novel mechanism of the "polar structure-induced electronic tunneling" effect has been proposed. The introduction of ILs facilitates the activation of hydrogen by FLP, and this effect becomes more pronounced as the carbon chain length of the ILs cations increases. Furthermore, the incorporation of [CTF3]- forms pseudo-FLP with FLP, further bolstering hydrogen activation efficiency. Electronic density analysis reveals that structural changes in ionic liquids do not alter the direction of electron transfer during the heterolytic hydrogen cleavage process. Instead, these changes enhance the electron transfer effect by increasing the electrophilicity and nucleophilicity of the system, thereby reducing the activation barrier and enhancing the efficiency of hydrogen activation. This study offers a novel perspective and valuable design principles for the construction of novel catalysts.