Formation of Ultrathin, Continuous Metal–Organic Framework Membranes on Flexible Polymer Substrates

Abstract

Metal–organic framework (MOF) materials have an enormous potential in separation applications, but to realize their potential as semipermeable membranes they need to be assembled into thin continuous macroscopic films for fabrication into devices. By using a facile immersion technique, we prepared ultrathin, continuous zeolitic imidazolate framework (ZIF‐8) membranes on titania‐functionalized porous polymeric supports. The coherent ZIF‐8 layer was surprisingly flexible and adhered well to the support, and the composite membrane could sustain bending and elongation. The membranes exhibited molecular sieving behavior, close to the theoretical permeability of ZIF‐8, with hydrogen permeance up to 201×10−7 mol m−2 s−1 Pa−1 and an ideal H2/CO2 selectivity of 7:1. This approach offers significant opportunities to exploit the unique properties of MOFs in the fabrication of separation and sensing devices.

Controlling the size and shape of Mg-MOF-74 crystals to optimise film synthesis on alumina substrates

“…The choice of tubular supports allows for the high surface area to volume ratios required for industrial separations. The growth of MOFs on modular supports such as tubular supports 34 and hollow fibres [35][36][37] has previously been demonstrated for ZIF-8 and UiO-66 but not for any of the M-MOF-74 series. We controlled the size of Mg-MOF-74 crystals via the addition of ethanol and water to synthesis solutions.…”

Ultrathin Membranes: A New Opportunity for Ultrafast and Efficient Separation

“…Beyond that, nanomaterial‐based membranes also show excellent performance in the field of gas separation. Ultrathin membrane technology has proven to be an energy‐efficient, cost‐effective, and environmentally benign approach to gas separation 74–82. Because the membrane pores serve as gas transport channels, decreasing the membrane thickness shortens the permeation path length of gas molecules, and is, therefore, an effective solution to achieve high permeance gas separation.…”

“…The development of assembling strategies that can effectively control the laminated structure of the membranes helps to improve the construction and regulation of mechanically stable transport channels. According to the structural features of different 2D nanomaterials, useful membrane‐fabrication technologies include vacuum filtration,76,81,82 spin coating,77 vacuum spin,78 hot‐drop coating,79 and in situ growth 80. These methods have been employed to prepare ultrathin laminar membranes with specific transport pathways such as slit‐like and molecular sieving pores, interlayer and interbundle spaces, and structural defects.…”

“…Laminar ultrathin membranes made of single‐atom‐thick nanosheets, especially GO nanosheets, have been successfully developed and show great potential in the field of gas separation 75–82. Ultrathin GO membranes for H 2 /CO 2 and H 2 /N 2 separation with thickness approaching 1.8 nm have been prepared by Yu's group via a facile filtration process ( Figure a–c).…”

Heteroepitaxial growth of vertically orientated zeolitic imidazolate framework‐L (Co/Zn‐ZIF‐L) molecular sieve membranes

“…Because of the flexible and precise control of pore architectures and network topologies, metal–organic frameworks (MOFs) have been proved to be promising for applications in areas such as gas storage and separation, 1, 2 catalysis, 3 drug delivery, 4 chemical sensing, 5 and liquid separation 6 . To date, the integration of MOFs with polymer materials, which is important for molecular sieve membranes, has been achieved by mixing them with a polymer matrix 7 or assembling a MOF layer on porous substrates 8 . Recently, the construction of continuous MOF films atop the porous substrates has represented a promising alternative to further enhance gas separation performance due to the maximization of MOF functionality.…”