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]