Manipulated Adsorption Of C8 Aromatics In MIL-53(Cr) Through Pre-Adsorbing Water Molecules

The flexible metal-organic framework MIL-53(Cr)has been demonstrated as efficient adsorbents for liquid phase adsorption and separation,while the effect of this attractive “breathing effect” on its performance remained uncertain.In this research,by increasing the amount of introduced water,MIL-53(Cr)first shrank into the narrow pore form through bound water,then re-opened due to the introduction of free water.Using MIL-53(Cr)with diverse amount of water addition as adsorbents,the liquid-phase adsorption and separation of C8 aromatics including o-xylene(OX),p-xylene(PX),m-xylene(MX)and ethylbenzene(EB)was manipulated by pre-adsorbed water in MIL-53(Cr).Pre-adsorbing water in MIL-53(Cr)induced a preference reversal between MX and PX,where dry samples preferentially adsorbed MX while high-water-addition samples preferred PX instead.In addition,the re-opened MIL-53(Cr)with high water addition hardly adsorbed EB,thereby increasing the selectivity of xylene isomers to EB.Longer equilibrium time was observed on MIL-53(Cr)with high water addition during which adsorption preference shifted from OX,MX to PX.Further molecular simulation verified the adsorption experiment results and provided a microscopic explanation for the adsorption behavior of water molecules and C8 aromatics in MIL-53(Cr).