Figure 3. Correlations between water permeance and (a) temperature, (b) viscosity for MOF-CH3@NH2 and MOF-CH3@CH3 membranes. (c) The dissolution activation energy of various solvents for MOF-CH3@NH2 and MOF-CH3@CH3 membranes. (d) Schematic illustration of water molecules dissolution behavior through pores on MOF-CH3@NH2 membrane surface.
To support above findings, molecular dynamics (MD) simulations were performed to probe the interaction energy of molecule-molecule and molecule-pore on molecule level. Specifically, they are calculated by Lennard-Jones interaction simulation (Figures 4d, e and Table S3). Results in Figures 4a and b show that the experimentally calculated E S values exhibit a linear relationship with that of simulated theoretical values (E T, kJ mol-1). Here, theE T value is acquired by subtracting molecule-molecule interaction energy from molecule-pore interaction energy, which represents the theoretical dissolution activation energy.E S and E T obey the equation of E S = KE T +C , where K is a proportionality constant. K value should vary with properties of membrane surface property and temperature, while C is determined by the physical factors of pore, e.g. , steric hindrance.[12] This equation further underpins that molecular dissolution behaviors are controlled by both molecule-molecule and molecule-pore interactions. It should be noted that some researchers calculated the interfacial resistance of molecule transporting through membrane to analysis molecule dissolution, while the resistance equation can not reveal the molecular dissolution capacity on molecule level.[57,58]