Controlling Metal Ion Counter Diffusion in Confined Spaces for In Situ Growth of Mixed Metal MOF Membranes for Gas Separation

Abstract

The development of facile, versatile strategies for the fabrication of mixed component metal‐organic framework (MOF) membranes is highly desired, but still very challenging due to the difficulty in controlling crystal growth rates of every single component in a specific confined space. It is difficult to adjust the formation of multicomponent MOF membrane in a controlled manner using conventional approaches such as secondary growth methods. Herein, we present a facile strategy that prepares the mixed metal zeolitic imidazolate framework (ZIF) membranes in situ in a confined space with nanostructure arrays under hydrothermal conditions using the counter diffusion mechanism. The counter diffusion of different metal ions from both the homogeneous bulk solution and the solid metal oxide nanostructure grown on substrate leads to the specific effective reaction zone by encountering with linker molecules at the interface. Subsequently, nucleation and crystal growth generate the continuous mixed metal MOF membranes. With this approach, a variety of mixed metal ZIF membranes were synthesized on different kinds of substrates. The prepared membranes exhibited good sieving effect to H2 and heavier gas molecules during both single and mixed gas permeation tests. This work opens a fresh avenue for the synthesis of mixed component MOF membranes, and the counter diffusion effect can be intentionally adopted to the design and fabrication of selective mixed metal MOF membrane on various supports.

Graphene Nanoribbon Hybridization of Zeolitic Imidazolate Framework Membranes for Intrinsic Molecular Separation

“…The H 2 /CO 2 separation performance was compared with that of previous membrane materials, including MOFs, zeolites, and two‐dimensional (2D) materials (Figure 3e and Table S2) [33–70] . Ideal separation performance (marked with a black star) of the ZIF‐8/GNR/alumina(300) membrane surpasses the upper bounds of reported polycrystalline MOF membrane performance and is located in the state art range of 2D materials‐based membranes (e.g.…”

NH2-MIL-125 Nanosheets Prepared via Crystallization Kinetics Modulation for Ultrathin Membrane Fabrication

“…The contra-diffusion synthetic protocol, which is featured with physical segregation of two precursor solutions containing metal ions and organic ligands, enabled concentration gradient-driven metal–ligand self-assembly, offering significant potential for the fabrication of ultrathin MOF membranes. This technique has garnered attention for its “self-regulating” capability, offering significant advantage in terms of ultrathin MOF membrane preparation. − Wang et al pioneered the preparation of continuous ZIF-8 membrane using contra-diffusion technique . Recently, a confined counterdiffusion strategy was further developed to enable epitaxial growth of (111)-oriented 165 nm thick UiO-66 membranes .…”

Interface Parallel Ionic Conformation Enhances the Nanoflow of Ionic Liquids Confined in the Silica Nanochannel

“…Recently, many studies have investigated the structure, , self-diffusion of ions, , and external force regulation , of confined ILs. Dong et al found that the migration of confined ILs in GO and MoS 2 membranes is different due to the discrepancy in ion interactions and diffusion.…”