To test the supposition that capillary-like adsorption is a general indicator of activation-collapse for any fluid, we extended our simulations of IRMOF-1 activation to a small library of common activation solvents. These simulations also enable us to test the experimental rule of thumb that activationcollapse behaviour is strongly related to solvent surface tension. ΔU ‡ act can be interpreted as the 240 surface excess energy associated with the interface between a gas and a liquid, which can be transformed to the surface tension by dividing by the interface area. In bulk systems, this is often assumed to be twice the cross-sectional area of the simulation box, as the minimum surface area in a gas-liquid mixture with equal volumes of each phase is a flat slab. Here we apply the same rationale to the fluids confined within the tortuous pore network of a MOF. Although it is impossible to make a 245 similar geometrical assumption to interfaces within a framework, we assume that the interface area is a function solely of the MOF structure i.e. is a constant value across all solvents tested. A result of this assumption is that ∆𝑈 𝑎𝑐𝑡 ‡ = 𝐴 𝑀𝑂𝐹 • 𝛾 𝑏𝑢𝑙𝑘 , where AMOF is the interface area between the more and less dense solvent phases in the MOF and γbulk is the bulk surface tension of the solvent. These data are plotted in Figure , demonstrating that the assumption is valid for the majority of solvents tested; 250 the assumption only breaks down in the case of solvents where mesophase behaviour was observed in their free energy curves i.e. acetonitrile and dioxane (open symbols). This phenomenon is a result of the reduced interface area between the dense and light solvent phases within the MOF (visualised in Figure ) -as AMOF decreases at constant γbulk, ΔU ‡ act correspondingly increases. The additional energy imparted on the framework by mesophase-forming solvents in turn leads to mechanical stress, thereby increasing the likelihood of framework collapse. Inspection of the simulated configurations show that mesophase-forming solvents have weaker solvent-MOF interaction energies compared to gas-like solvents (Figure ), signifying a preference to cluster with 265 other solvent molecules within the pores. In contrast, gas-like solvents preferentially adsorb to the framework ahead of other sorbate molecules, preventing the formation of cohesive phases and interfaces within the MOF. Extrapolating to macroscopic behaviour, our simulations indicate that MOF solvophilicity (i.e. the affinity of the solvent towards the MOF) is a greater predictor of successful activation than bulk surface tension. Overall, these findings largely agree with the prevailing theory of 270 activation-collapse -that capillary stresses can lead to physical degradation of the framework however our results challenge the supposition that bulk surface tension is a good indicator.