Controlling Gas Selectivity in Molecular Porous Liquids by Tuning the Cage Window Size

Abstract

Control of pore window size is the standard approach for tuning gas selectivity in porous solids. Here, we present the first example where this is translated into a molecular porous liquid formed from organic cage molecules. Reduction of the cage window size by chemical synthesis switches the selectivity from Xe-selective to CH 4 -selective, which is understood using 129 Xe, 1 H, and pulsed-field gradient NMR spectroscopy.Porous liquids (PLs) are a new class of porous material.

Melt-Quenched Porous Organic Cage Glasses

“…Since the initial conceptualisation of porous liquids in 2007, 24 POCs have been the basis of investigations into both Type 1 porous liquids (that is, neat liquids formed from molecules containing permanent cavities) and Type 2 porous liquids (that is, solutions of a porous material in a cavity-excluded solvent). 17,[25][26][27][28] For Type 1 porous liquids, and of particular relevance to this work, POCs that were externally decorated with alkyl groups were synthesised in an attempt to form neat liquid POCs, although a neat Type 1 porous liquid was not fully realised due to interpenetration of the alkyl chains into the cage cavities. 29,30 Moreover, while melting points were reported, the potential glass-forming behaviour of these alkylated POCs was not investigated.…”