Reversed thermo-switchable molecular sieving membranes composed of two-dimensional metal-organic nanosheets for gas separation

Abstract

It is highly desirable to reduce the membrane thickness in order to maximize the throughput and break the trade-off limitation for membrane-based gas separation. Two-dimensional membranes composed of atomic-thick graphene or graphene oxide nanosheets have gas transport pathways that are at least three orders of magnitude higher than the membrane thickness, leading to reduced gas permeation flux and impaired separation throughput. Here we present nm-thick molecular sieving membranes composed of porous two-dimensional metal-organic nanosheets. These membranes possess pore openings parallel to gas concentration gradient allowing high gas permeation flux and high selectivity, which are proven by both experiment and molecular dynamics simulation. Furthermore, the gas transport pathways of these membranes exhibit a reversed thermo-switchable feature, which is attributed to the molecular flexibility of the building metal-organic nanosheets.

A Facile, High‐Yield, and Freeze‐and‐Thaw‐Assisted Approach to Fabricate MXene with Plentiful Wrinkles and Its Application in On‐Chip Micro‐Supercapacitors

“…The volume expansion can lead to the breakage of the van der Waals bond in the layered materials, facilitating the exfoliation of 2D nanosheets. Therefore, the freeze‐and‐thaw strategy is widely used in the exfoliation of some common 2D materials like metal organic framework (MOF) nanosheets, BNNS, GO, montmorillonite (MMT) nanosheets, and Sb 2 Se 3 nanosheets . However, the mentioned yield was less than satisfactory like BNNS (only 0.120% for h‐BN).…”

“…In an effort to solve this problem, we proposed a freeze‐and‐thaw (FAT)‐assisted method to cleave MXene nanosheets from m‐MXene via water‐freezing expansion force. The FAT method is commonly utilized in the exfoliation of several 2D nanomaterials, including metal–organic nanosheets, boron nitride nanosheets (BNNSs), graphene oxide (GO), and antimony triselenide (Sb 2 Se 3 ) In contrast, the FAT method might be more suitable for MXene. Due to the selective etch of Al atom layer of MAX, the obtained m‐MXene is accordion‐like, and thus exists wider interstices between interlayer, which may be helpful to the intercalation of ample water molecules to swell .…”

Switching in Metal–Organic Frameworks

“…Some of these responses generate observable properties that may seem counterintuitive. In one such case, Zhao's group exfoliated and purified nanosheets of MAMS‐1, a nickel‐based MOF with robust bonds within a layer, with connected layers affixed to one another through individually weak van der Waals interactions . This MOF possesses two distinct, perpendicular apertures.…”

Schalten in Metall‐organischen Gerüsten

“…Zum Beispiel exfolierten und reinigten Zhao et al. Nanoblätter von MAMS‐1, einem nickelbasierten MOF mit robusten Bindungen innerhalb einer Schicht, wobei die Schichten durch schwache Van‐der‐Waals‐Wechselwirkungen miteinander verbunden sind . Dieses MOF hat zwei unterschiedliche, senkrecht zueinander stehende Öffnungen.…”