Molecular dissolution behaviors on porous membrane surface using
hierarchical metal-organic framework lamellar membrane
Lamellar membranes, especially assembled by microporous framework
nanosheets, have excited interest for fast molecular permeation.
However, the underlying molecular dissolution behaviors on membrane
surface, especially at pore entrances, remain unclear. Here,
hierarchical metal-organic framework (MOF) lamellar membranes with 7
nm-thick surface layer and 553 nm-thick support layer are prepared.
Hydrophilic (–NH2) or hydrophobic (–CH3) groups are decorated at pore
entrances on surface layer to manipulate wettability, while –CH3 groups
on support layer provide comparable, low-resistance paths. We
demonstrate that molecular dissolution behaviors are determined by
molecule-molecule and molecule-pore interactions, derived from intrinsic
parameters of molecule and membrane. Importantly, two dissolution model
equations are established: for hydrophobic membrane surface, dissolution
activation energy (ES) obeys ES=Kmln[(γL-γC)μd2], while turns to
ES=Kaln[(γL-γC)δeμd2] for hydrophilic one. Particularly, hydrophilic
pore entrances exert strong interaction with polar molecules, thus
compensating the energy consumed by molecule rearrangement, giving fast
permeation (> 270 L m-2 h-1 bar-1).