Computational Screening of MOFs and Zeolites for Direct Air Capture of Carbon Dioxide under Humid Conditions

With
rising CO2 levels, it is important to develop new
methods to capture CO2 directly from air. Currently, most
direct air capture (DAC) adsorbents, such as amines, rely on chemisorption.
However, finding materials with weaker, reversible adsorption could
improve the regenerability of these adsorbents. The low concentration
of CO2 relative to other components of air and the presence
of humidity limit the effectiveness of physisorbent materials for
DAC. In this work, we screened the 2014 computation-ready, experimental
metal–organic framework (CoRE MOF) database along with silica
zeolites, aluminophosphate (AlPO) zeolites, and gallophosphate (GaPO)
zeolites for DAC under humid conditions based on heat of adsorption
criteria. After the initial assessment, AlPO and GaPO zeolites appeared
to be promising adsorbents for DAC. To assess the accuracy of these
initial predictions, we compared adsorbate–adsorbent interaction
energies predicted by the force field used in screening (UFF) and
dispersion-corrected density functional theory. To improve the accuracy
of these predictions, first-principles force fields were fit for AlPO
and GaPO zeolites. More accurate CO2 and H2O
heats of adsorption and adsorption isotherms were computed and showed
that AlPO and GaPO zeolites are not suitable for DAC applications.