Polyethyleneimine functionalised nanocarbons for the efficient adsorption ofcarbon dioxide with a low temperature of regeneration

Polyethyleneimine (PEI) conjugates with a range of nanocarbons (NCs) have been prepared, and their performances with regard to carbon dioxide absorption and liberation are compared.PEI-functionalised multi-walled carbon nanotubes (PEI-MWNTs) prepared by the reaction of branched PEI (25,000 Da) with F-MWNTs in the presence of pyridine, showed a lower CO 2 capacity at 25 C (5 wt%, 1.1 mmol CO 2 /g adsorbent) as compared to PEI-SWNTs (9.2 wt%, 2.1 mmol CO 2 /g adsorbent), consistent with the interior layers of the MWNTs adding weight to the base NC without adding functionality.PEI-functionalised graphite/graphene was prepared by three routes: fluorinated graphite intercalation compounds, prepared from natural graphite powder, were reacted with PEI in EtOH with pyridine; exfoliated natural graphite powder was reacted with Boc-Phe(4-N 3 )-OH, and subsequently PEI to give PEI-Phe(4-N-G); graphite oxide (GO) was reacted with PEI in the presence of NEt 3 to give PEI-GO.The CO 2 capacity of PEI-GO at 25 C (8 wt%, 1.8 mmol CO 2 /g adsorbent) was comparable to that of PEI-SWNTs making GO a valid and cheaper alternative to the SWNT scaffold.The temperature of CO 2 desorption of the PEI-NCs was 75 C, providing a lower energy load for regeneration compared to current amine-based scrubbing units.The rate of CO 2 uptake is seen to depend on the curvature of the NC substrate.