Effect of adsorbent history on adsorption characteristics of MIL-53(Al) metal organic framework.

Structural transformation of MIL-53(Al) metal organic framework from large pore to narrow pore form (lp → np) or vice versa is known to occur by adsorption of certain guest molecules, by temperature change or by applying mechanical pressure. In this work, we perform a systematic investigation to demonstrate that adsorbent history also plays a decisive role in the structural transitions of this material (and hence on its adsorption characteristics). By changing the adsorbent history, parent MIL-53(Al) is tuned into its np domain at ambient temperature such that it not only exhibits a significant increase in CO2 capacity, but also shows negligible uptake for CH4, N2, CO, and O2 at subatmospheric pressure. In addition, for the high pressure region (1-8 bar), we propose a method to retain the lp form of the sample to enhance its CO2 uptake.