Towards environmentally benign capture and conversion: heterogeneous metal catalyzed CO₂ hydrogenation in CO₂ capture solvents

The transformation of captured CO2 into value-added chemicals to mitigate increasing CO2 concentration in the atmosphere has gained significant attention recently. Though carbon capture and storage (CCS) is already being practiced in a few places, it suffers from energy-intensive CO2 desorption and compression steps involved, which can be avoided in the carbon capture and utilization (CCU) approach. Herein, a selection of carbon capture solvents were screened to assess the reactivity of condensed-phase heterogeneous metal catalyzed hydrogenation of CO2. Among the catalysts screened, the Cu/ZnO/Al2O3 catalyst was active for the one-pot CO2 capture and conversion process to methanol using post and pre-combustion carbon capture solvents comprised of various amines and alcohols. Our findings indicate that formamides are less-reactive under our conditions in comparison with formate ester intermediates and a combination of 1° alcohols and amines gives the highest methanol yield. Screening volatile organic compound (VOC)-free alcohols and amines led us to an environmentally benign system of bio-derived and biodegradable chitosan and polyethylene glycol (PEG200), which provide a moderate concentration of methanol (139.5 mmol L−1) with the facile separation of volatile products (water and methanol). The chitosan/PEG200 system was recycled three times, ultimately providing a promising VOC-free, biodegradable, bio-derived and recyclable CO2 capture and conversion pathway.