Conformational-change-induced selectivity enhancement of CAU-10-PDC membrane for H2/CH4 and CO2/CH4 separation

초록

The separation of H<inf>2</inf>/CH<inf>4</inf> or CO<inf>2</inf>/CH<inf>4</inf> is critical to the purification of natural gas. Herein, we report on novel membranes with a metal-organic framework of CAU-10-PDC for the separation of these two mixtures. The dense CAU-10-PDC membranes are fabricated on a porous alumina support using the seeded growth method. An unexpected increase in selectivity was observed while testing mixed gas permeation with either H<inf>2</inf>/CH<inf>4</inf> or CO<inf>2</inf>/CH<inf>4</inf> at a molar ratio of 50:50. Steady-state selectivity reached 101 for H<inf>2</inf>/CH<inf>4</inf> and 62 for CO<inf>2</inf>/CH<inf>4</inf>. Ideal selectivity measured from single gas permeation reached 475 for H<inf>2</inf>/CH<inf>4</inf> and 288 for CO<inf>2</inf>/CH<inf>4</inf>. Molecular dynamics simulations and time-resolved X-ray diffraction with a synchrotron radiation source were used to probe conformational changes in CAU-10-PDC induced by exposure to CH<inf>4</inf>. When exposed to an atmosphere containing CH<inf>4</inf>, CAU-10-PDC presented a change in the space group (from I4<inf>1</inf>/amd to I4<inf>1</inf>), which drastically reduced the pore limiting diameter from 4.15 to 2.95 Å, rendering the channel nearly impermeable to CH<inf>4</inf>. © 2021

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