Molecular dissolution behaviors on porous membrane surface using hierarchical metal–organic framework lamellar membrane

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 (-NH 2 ) or hydrophobic (-CH 3 ) groups are decorated at pore entrances on surface layer to manipulate wettability, while -CH 3 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 (E S ) obeys E S = K m ln[(γ L -γ C )μd 2 ], while turns to E S =K a ln [(γ L -γ C )δ e μd 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 À2 h À1 bar À1 ).

ZSM‐5 zeolite incorporated flow battery membranes with regulated pore channels for high proton conduction

“…Ion conductive membranes (ICMs) with fast proton conduction characteristics are of importance for the development of high‐power energy conversion and storage devices 1 . Currently, microporous framework materials possessing rigid well‐defined microporous structure, 2 such as metal organic framework (MOF), 3 covalent organic framework (COF), 4 and zeolite 5 are promising materials employed to prepare ICMs for fuel cell and flow battery 6 . Among these microporous materials, ZSM‐5 is an aluminosilicate porous zeolite composed of TO 4 (T = Si 4+ , Al 3+ ) tetrahedral primary units (Figure S1), 7 whose hydrophilic property on the surface could reduce the resistance to the entry of protons into the pore, 8 and the internal interconnected sub‐nanometer pores may allow fast proton transport, 9 showing tremendous potential for the development of the high‐performance ICM 10 .…”