Modeling Water and Ammonia Adsorption in Hydrophobic Metal–Organic Frameworks: Single Components and Mixtures

Capturing
ammonia under humid conditions is difficult because chemical
functionalities that attract ammonia tend to also attract water. In
this work, three hydrophobic metal–organic frameworks (MOFs)
were assessed for ammonia capture under dry and humid conditions.
Using grand canonical Monte Carlo simulations, pure water isotherms
were calculated and showed good agreement with experiment. The low
heats of adsorption for water substantiate the hydrophobic nature
of these MOFs. Simulated ammonia isotherms predict that hydrophobic
MOFs adsorb similar amounts of ammonia under dry and humid conditions.
These results suggest that hydrophobic MOFs could be appropriate candidates
for ammonia capture under humid conditions. The simulations also provide
detailed information on the behavior of water and mixtures of water
and ammonia confined in hydrophobic pores.