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 CH4‐selective, which is understood using 129Xe, 1H, and pulsed‐field gradient NMR spectroscopy.

Key Parameters to Tailor Hollow Silica Nanospheres for a Type I Porous Liquid Synthesis: Optimized Structure and Accessibility

“…In the literature, porous liquids have been mainly proposed for gas capture applications [ 10 ]. They exhibit remarkable properties such as fast gas diffusion, high gas solubilities [ 6 , 9 ] and are promising for gas separation thanks to modular selectivities [ 11 ]. More recently, they were shown as tailorable and tunable materials for gas transport and sorbent [ 11 , 12 , 13 ].…”

“…They exhibit remarkable properties such as fast gas diffusion, high gas solubilities [ 6 , 9 ] and are promising for gas separation thanks to modular selectivities [ 11 ]. More recently, they were shown as tailorable and tunable materials for gas transport and sorbent [ 11 , 12 , 13 ]. However, as porous solid materials that find use in broader applications [ 14 , 15 , 16 , 17 ] (drug delivery, energy storage and conversion, catalysis, optical, adsorption, separation, sensing, etc.…”

Xenon binding by a tight yet adaptive chiral soft capsule

“…This makes xenon binding very challenging. Several macrocycle and cage compounds, including hemicarcerands 14,15 , cyclodextrins 16,17 , calixarenes [18][19][20][21] , cryptophanes [22][23][24][25][26][27][28][29][30] , cucurbiturils [31][32][33][34][35][36][37] , and recent porous imine cages [38][39][40] have been explored for xenon binding, in solution or solid state. Cryptophanes are shown to be outstanding in terms of high affinity and competence for biosensing applications 8,9,13,41,42 , though, tedious synthesis and sometimes chiral resolution of the intrinsic enantiomers are required for chirality-sensitive detection [43][44][45] .…”

Modular Type III Porous Liquids based on Porous Organic Cage Microparticles

“…Previously, analytical techniques such as IR and NMR spectroscopy, or gas displacement measurements, were used to probe the gas solubility in POC-derived Type II porous liquids. [13][14][15]18] Here, the use of bulky liquids with high boiling points and low vapour pressures allowed us to study the gas solubility using more standard sorption measurements that are used for porous solids. Specifically, the use of a Quantachrome Nova instrument, benchmarked to known uptakes in liquids and with stirring to ensure that the liquids reached saturation uptake, allowed different gases to be screened and adsorption isotherms to be obtained (see ESI, Section 1, for more information).…”

“…[13][14][15] There have also been attempts to decorate cages with long alkyl chain functionality to lower the melting points in the preparation of Type I porous liquids. [16,17] Some of the properties of POCs can be retained when transferred into the liquid state, such as size-selective guest uptake, [18] while others, such as chiral recognition, [14] are lost. One potential way to retain the solid-state properties of POCs is to form Type III porous liquids, rather than Type I or Type II systems.…”