Figure 6. (a) Dye rejection, (b) cyclic operation measurement,
(c) pressure cyclic measurement, and (d) methanol permeance and RR
rejection against operation time for
MOF-CH3@NH2 and
MOF-CH3@CH3 membranes.
4 CONCLUSIONS
In summary, hierarchical MOF lamellar membranes with ultrathin surface
layer (~ 7 nm) and low-resistance support layer (553 nm)
were prepared by double-needled electrostatic atomization technology.
The wettability of pore entrances on surface layer is subtly adjusted by
hydrophilic (–NH2) and hydrophobic
(–CH3) groups. While the inner pores with
–CH3 groups provide identical and low-resistance
diffusion paths in support layer.
Based on this novel platform, the
underlying molecule dissolution behaviors are systematically
investigated from the viewpoint of dissolution activation energy
(E S). we demonstrate that molecule-pore and
molecule-molecule interactions play crucial roles for dissolution
process. For hydrophobic membrane surface, E S is
above 0 for both polar and nonpolar solvents, confirming the negative
tendency for molecules to dissolve into pore entrances. In contrast, for
hydrophilic membrane surface,E S is above
0 for nonpolar solvents but below 0 for polar solvents, suggesting that
polar solvents can actively dissolve into pore entrances. This is
ascribed to the hydrophilic groups exert strong interactions with polar
solvents, thus compensating the energy consumed by molecule
rearrangement, thus permitting fast permeation (over 270 L
m-2 h-1 bar-1 for
acetone). Significantly, dissolution model equations on hydrophilic and
hydrophobic membrane surface are established, respectively, which are
stemmed from the intrinsic parameters of molecules (μ ,δ e γ L, d ) and
membrane surface (γ C). This elucidating molecular
dissolution behaviors on porous membrane surface would provide new
guidelines for the design of advanced membranes.
ACKNOWLEDGEMENTS
The authors would like to acknowledge the financial support from
National Natural Science Foundation of China
(U2004199),
Excellent Youth Foundation of Henan Province (202300410373) and China
Postdoctoral Science Foundation
(2022TQ0292).
Center for advanced analysis and computational science, Zhengzhou
University is also highly acknowledged.