Nordic Consortium for CO2 Conversion

A method for the synthesis of benzoic acids from aryl iodides using two of the most abundant and sustainable feedstocks, carbon dioxide (CO2) and water, is disclosed. Central to this method is an effective and selective electrochemical reduction of CO2 to CO, which mitigates unwanted dehalogenation reactions occurring when H2 is produced via the hydrogen evolution reaction (HER).

Sustainable methanol formation from CO2/H2 is potentially a key process in the post-fossil chemical industry. In this study, Hf- and Zr-based metal-organic framework (MOF) materials with UiO-67 topology, functionalized with Pt nanoparticles, have been tested for CO2 hydrogenation at 30 bar and 170–240°C. The highest methanol formation rate, 14 molmethanol molPt−1 h−1, was obtained over a Hf-based catalyst, compared with the maximum of 6.2 molmethanol molPt−1 h−1 for the best Zr-based analogue. However, changing the node metal did not significantly affect product distribution or apparent activation energy for methanol formation (44–52 kJ mol−1), strongly indicating that the higher activity of the Hf-based analogues is associated with a higher number of active sites. Both catalysts showed stable catalytic performance during testing under kinetic conditions, but the addition of 2 vol% water to the feed induced catalyst deactivation, in particular the Hf-MOFs. Interestingly, mainly methanol and methane formation rates decreased, while CO formation rates were less affected by deactivation. No direct correlation was found between catalytic stability and framework stability (crystallinity, specific surface area). Experimental and computational studies suggest that water adsorption strength to the MOF node may affect the relative catalytic stability of Hf-UiO-67-Pt versus Zr-UiO-67-Pt methanol catalysts.

We have employed computational methods to investigate the iridium-catalyzed allylic substitution leading to the formation of enantioenriched allyl carbamates from carbon dioxide (CO2). The reaction occurs in several steps, with initial formation of an iridium-allyl, followed by nucleophilic attack by the carbamate formed in situ from CO2 and an amine. A detailed isomeric analysis shows that the rate-determining step differs for the (R)- and (S)-pathways. These insights are essential for understanding reactions involving enantioselective formation of allyl carbamates from CO2.