Exfoliation of 2D Metal‐Organic Frameworks: toward Advanced Scalable Materials for Optical Sensing

Abstract

Two‐dimensional metal‐organic frameworks (MOFs) occupy a special place among the large family of functional 2D materials. Even at a monolayer level, 2D MOFs exhibit unique sensing, separation, catalytic, electronic, and conductive properties due to the combination of porosity and organo‐inorganic nature. However, lab‐to‐fab transfer for 2D MOF layers faces the challenge of their scalability, limited by weak interactions between the organic and inorganic building blocks. Here, comparing three top‐down approaches to fabricate 2D MOF layers (sonication, freeze‐thaw, and mechanical exfoliation), The technological criteria have established for creation of the layers of the thickness up to 1 nm with a record aspect ratio up to 2*10^4:1. The freezing‐thaw and mechanical exfoliation are the most optimal approaches; wherein the rate and manufacturability of the mechanical exfoliation rivaling the greatest scalability of 2D MOF layers obtained by freezing‐thaw (21300:1 vs 1330:1 aspect ratio), leaving the sonication approach behind (with a record 900:1 aspect ratio) have discovered. The high quality 2D MOF layers with a record aspect ratio demonstrate unique optical sensitivity to solvents of a varied polarity, which opens the way to fabricate scalable and freestanding 2D MOF‐based atomically thin chemo‐optical sensors by industry‐oriented approach.

Layered nanomaterials for renewable energy generation and storage

“…118,119 There are many 2D materials with various properties, among which graphene and graphene derivatives are particularly distinguished: graphene oxide (GO), reduced graphene oxide (rGO), 14,120 and graphene nanosheets. 121 The following 2D-material are also widely used: MXenes, 122,123 metal–organic frameworks (MOFs), 124,125 transition metal dichalcogenides (TMDs), 126 covalent organic frameworks (COFs), 127 2D coordinated polymer. 128…”

Gallium-based liquid metals as reaction media for nanomaterials synthesis

“…Metal–organic frameworks (MOFs) represent a category of porous polymeric materials, wherein metal ions are interconnected by organic bridging ligands. 134 MOFs have attracted wide interest in the fields of energy storage, 135 small molecule detection, 136 optical sensors, 137 catalysis, 138 and electromagnetic wave absorption due to their excellent properties such as high internal surface area, tunable pore size, ordered crystal structure, and excellent chemical stability. 136,139 Ga-based LMs have demonstrated impressive capabilities as fluid electrodes in the electrochemical synthesis of MOFs.…”

Two-dimensional thin and porous membranes for gas molecules sensing

“…However, the challenge is in the preparation of the ultrathin (up to 1 nm) and large-area high-quality MOF membranes due to a limited possibility for the growth of arbitrary MOFs by the bottom-up methods and the lack of control for top-down methods [3]. Here, we report on top-down exfoliation technique for 2D MOF and their optical application in gas molecules detection [4].…”