Fig. 8. Study of host–guest chemistry in the porous liquid by diffusion NMR. (a) Measured viscosities and calculated apparent solvodynamic radii (R S) of scrambled cages in the porous liquid at different concentrations. The viscosity increases with concentration but the apparent size of cage remains constant, suggesting that no aggregation in solution is occurring; (b) diffusion NMR measurements for CH4 in PCP and the porous liquid show an ∼3-fold increase in the apparent size (R S) of the gas and a strong shielding effect, both suggesting a dynamic host–guest equilibrium between the cage and CH4 (empty host cage = black squares; free CH4 guest in neat PCP = pink square; pink-filled black square = CH4/cage host–guest complex) (c) addition of CHCl3 to the CH4-saturated porous liquid shows displacement of the CH4, with a subsequent decrease in apparent size and reduced shielding effect for CH4; at the same time, a ∼4 fold increase in the apparent size (R S) of the CHCl3 is observed, along with a strong shielding effect, again suggesting a dynamic host–guest equilibrium between the cage and CHCl3 (free CHCl3 guest in neat PCP = green square, green-filled black square = CHCl3/cage host–guest complex); (d) addition of 1-t-butyl-3,5-dimethylbenzene (tBu, orange squares) to the CH4-saturated porous liquid shows no displacement of CH4, and no apparent increase in size (R S) or shielding effect of the bulky tBu-solvent, confirming that it is size-excluded from the cage cavity.
