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.