Cross-Linking Amine-Rich Compounds into High Performing Selective CO2 Absorbents

Amine-based absorbents play a central role in CO2 sequestration and utilization. Amines react selectively with CO2, but a drawback is the unproductive weight of solvent or support in the absorbent. Efforts have focused on metal organic frameworks (MOFs) reaching extremely high CO2 capacity, but limited selectivity to N-2 and CH4, and decreased uptake at higher temperatures. A desirable system would have selectivity (cf. amine) and high capacity (cf. MOF), but also increased adsorption at higher temperatures. Here, we demonstrate a proof-of-concept where polyethyleneimine (PEI) is converted to a high capacity and highly selective CO2 absorbent using buckminsterfullerene (C-60) as a cross-linker. PEI-C-60 (CO2 absorption of 0.14 g/g at 0.1 bar/90 degrees C) is compared to one of the best MOFs, Mg-MOF-74 (0.06 g/g at 0.1 bar/90 degrees C), and does not absorb any measurable amount of CH4 at 50 bar. Thus, PEI-C-60 can perform better than MOFs in the sweetening of natural gas.