Predicting Low-Pressure O2 Adsorption in Nanoporous Framework Materials for Sensing Applications

A set of 98 nanoporous framework material (NFM) structures was investigated by classical Grand canonical Monte Carlo simulations for low-pressure O-2 adsorption properties (Henry's constant and isosteric heat of adsorption). The set of materials includes those that have shown high O-2 uptake experimentally as well as a subset of more than 2000 structures previously screened for noble-gas uptake. While use of the general force field UFF is fruitful for noble-gas adsorption studies, its use is shown to be limited for the case of O-2 adsorptionone distinct limitation is a lack of sufficient O-2-metal interactions to be able to describe O-2 interaction with open metal sites. Nonetheless, those structures without open metal sites that have very small pores (<2.5 angstrom) show increased O-2/N-2 selectivity. Additionally, O-2/N-2 mixture simulations show that in some cases, H2O or N-2 can hinder O-2 uptake for NFMs with small pores due to competitive adsorption.