Improved CO2 capture and separation performances of a Cr-based metal–organic framework induced by post-synthesis modification of amine groups

Abstract

A composite adsorbent based on a metal–organic framework MIL-101 (Cr3F(H2O)2O(BDC)3; BDC: terephthalic acid) loaded with N,N′-dimethylethylenediamine (dmeda) was synthesized by post-synthesis modification method, and the crystal structure and thermal stability of MIL-101 were maintained. The composite is shown to enhance capacity and selectivity for post-combustion carbon dioxide capture, even if its BET specific surface area decreases by 52% compared to MIL-101. At 273 K and 298 K under 1 bar, dmeda-MIL-101 exhibited 8.7% and 18.7% increase in CO2 capacity respectively (from 2.30 mmol/g of MIL-101 to 2.50 mmol/g at 273 K, and from 1.35 mmol/g of MIL-101 to 1.59 mmol/g at 298 K). At 273 K and 298 K under a 0.15 bar CO2/0.75 bar N2 mixture, the CO2/N2 selectivities of MIL-101 and dmeda-MIL-101 were calculated by Ideal Adsorbed Solution Theory (IAST), according to single-component gas sorption experiment data. The improved capacity and selectivity are consequences of the higher isosteric heat of CO2 adsorption (33.9 kJ/mol at zero coverage), which is due to the interaction between amines and CO2.