Determination of the pore size distribution and network connectivity in microporous solids by adsorption measurements and Monte Carlo simulation

We carried out Monte Carlo simulations of the adsorption of three species-CH4, CF4, and SF6-in model pores of various sizes. By comparing the simulated isotherms, integrated over a pore size distribution, with experimental isotherms for the adsorption of these species on a microporous carbon, estimates of the pore size distribution (PSD) of the carbon were obtained-one for each adsorptive. Because the adsorptives have different molecular sizes and strengths of interaction with the adsorbent, they probe different ranges of pore size; each adsorptive thus provided a partial PSD. By combining the partial PSDs, we were able to obtain a much more complete PSD than could be obtained with a single adsorptive. Comparison of the PSDs obtained with CF4 and SF6, which substantially overlap, shows molecular sieving. By analyzing these two PSDs, using percolation theory, we extracted an estimate of the connectivity of the pore network, an important determinant of the transport properties of the solid. Our approach is applicable to microporous solids in general.