Abstract
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
–CH3groups 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 (E S) obeysE S=K mln[(γ L-γ C)μd 2],
while turns toE S=K aln[(γ L-γ C)δ eμd 2]
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-1bar-1).