Modelling gas storage capacity for porous aromatic frameworks

This paper examines the gas storage capacity of recently developed high-porosity materials known as porous aromatic frameworks (PAFs). We develop a mathematical model to examine the gravimetric and volumetric uptake capacities of both hydrogen and methane for PAFs. Our results indicate that hydrogen gravimetric and volumetric uptakes of PAF-301, PAF-302, PAF-303 and PAF-304 at 77 K and 100 bar are (1.09 wt.%, 9.14 g/L), (6.43 wt.%, 20.26 g/L), (12.62 wt.%, 20.34 g/L) and (19.80 wt.%, 19.77 g/L), respectively. The gravimetric uptakes of PAF-303 and PAF-304 are reasonably high, while their volumetric uptakes are relatively low due to their very low bulk densities. Although high porosity is an important criterion for the design of gas-storage materials, our results show that it is not the dominating factor for determining gas-storage capacity of porous materials. A porous material with reasonably high porosity together with selectively highly-interacting components and a reasonable bulk density will have a higher storage capacity than materials with high porosities, such as PAF-304.