From simulations in IRMOF-1 (Figure ), we proposed that solvent mesophase formation reduces the solvent interfacial surface area of the MOF, leading to larger ΔU ‡ act and therefore increased likelihood of metal-ligand bond breaking. Given the results from IRMOF-4 and -5 (i.e. no measurable energy barrier during solvent desorption, Figure ) it appears that there is a minimum pore window diameter required for the formation of solvent mesophases. Further, larger windows (and to a lesser extent 300 larger pore diameters) correspond to both greater ΔU ‡ act overall and a greater difference in ΔU ‡ act between acetonitrile and dichloromethane for a given framework. As a result, we conclude that solvent interfaces form across the pore window, agreeing with the hypothesis of capillary-like desorption leading to activation-collapse. This new understanding, alongside the insight that mesophase formation is promoted by relatively low MOF-sorbate affinities, can lead to the 305 identification of specific solvents with low likelihood of activation-collapse for a specific MOF.