Combined CO₂ Capture and Hydrogenation to Methanol: Amine Immobilization Enables Easy Recycling of Active Elements

Amines were immobilized onto solid supports and employed for tandem CO₂ capture and conversion to CH₃ OH using homogeneous hydrogenation catalysts. The hydrogenation proceeded through the formation of formamide intermediates. After hydrogenation, the immobilized amines were easily filtered and collected to be reused. The catalyst and methanol were recovered from the filtrate. Covalently-attached (to polymer support or silica) amine functionalities displayed the highest recycling potential with almost no leaching under the hydrogenation reaction conditions. Using polyethylenimine grafted onto a solid-silica support, the catalyst and amine were successfully recycled, and CO₂ (either pure or from the air) was efficiently captured and converted to CH₃ OH over multiple cycles.