Computational Study on the Influences of Framework Charges on CO2 Uptake in Metal-Organic Frameworks

This work involved a computational study to investigate the influences of framework charges on CO2 uptake in metal-organic frameworks (MOFs), in which a total of 20 MOFs with different topologies, pore sizes, and chemical characteristics were examined. The results showed that, at atmospheric pressure, the contribution of the framework charges is generally large, and a linear relationship with pore size was found, showing that, when the pore size is larger than 3.3 nm, the contribution becomes smaller than 10%. On the other hand, the framework charge contribution was found to decrease rapidly with increasing pressure and to become less than 10% at pressures higher than 2.0 MPa. This work shows that the framework charge contribution in MOFs cannot be ignored in computational screening of MOF materials for CO2 capture under low-pressure conditions, whereas at moderate operating pressures, the contribution can be ignored in large-scale prescreening Such as in the natural gas upgrading process.