Molecular simulations of the gas permeance of non-polar molecules through the BTESE-derived membranes

DL Jin and T Zhang and MA Xiong and XX Ren and M Guo and Y Pan and J Zhong, SEPARATION AND PURIFICATION TECHNOLOGY, 376, 133717 (2025).

DOI: 10.1016/j.seppur.2025.133717

Gas permeance is of particular importance for the design of the porous organosilica materials such as 1,2-bis(triethoxysilyl)ethane (BTESE) membrane. While the interplay between the gas permeance, driving pressure, and molecular size remains to be better understood. In this work, we first construct the molecular model consisting of the BTESE- derived membrane sandwiched between two gas reservoirs. By using two pistons, these gas reservoirs are held at two constant pressures, leading to a driving force for gas molecules. We then employ the molecular dynamics simulations to determine the gas permeance under several different driving pressures. For this BTESE-derived membrane, the gas permeance is shown to be decreased as the driving pressure increases. These observations can be readily explained by the adsorption theory and the Knudsen number. In particular, the relation between gas permeance and driving pressure is found to be dependent of the molecular size and the effective pore size. Moreover, the potential mean force as well as the energy barrier (to enter the pores of the BTESE-derived membrane) is estimated from the density curve. The positive correlation between the driving pressure and the energy barrier has validated the above descriptions. By applying two relations in the above, the gas permeance is shown to be proportional to the energy barrier. These findings provide a means to probe the gas permeance from the density curve and the potential mean force.

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