Chemically Delaminated Free‐Standing Ultrathin Covalent Organic Nanosheets

Abstract

Covalent organic nanosheets (CONs) are a new class of porous thin two‐dimensional (2D) nanostructures that can be easily designed and functionalized and could be useful for separation applications. Poor dispersion, layer restacking, and difficult postsynthetic modifications are the major hurdles that need to be overcome to fabricate scalable CON thin films. Herein, we present a unique approach for the chemical exfoliation of an anthracene‐based covalent organic framework (COF) to N‐hexylmaleimide‐functionalized CONs, to yield centimeter‐sized free‐standing thin films through layer‐by‐layer CON assembly at the air–water interface. The thin‐layer fabrication technique presented here is simple, scalable, and does not require any surfactants or stabilizing agents.

2D-enabled membranes: materials and beyond

“…Class 2 membranes are classified as 2D membranes that utilize nanosheets with intrinsic (in-plane) microporosity on the basal plane. Nanosheets with intrinsic microporosity capable of differentiating molecular size differences up to 0.01-0.05 nm are exploited in this class of membranes [18][19][20]. This intrinsic microporosity is different from external microporosity of the class 1 membranes and also differentiates itself from the intrinsic defects formed in 2D materials.…”

Amorphous 2D materials containing a conjugated-polymer network

“…Although amorphous states were observed in frameworks and layered materials [26][27][28][29][30][31][32][33] , the amorphous nature was not applied to the exfoliation. A recent report shows that grafting of bulky alkyl chains on the layer of a COF induced smooth exfoliation into the nanosheets 34 . If amorphous organic layered materials consisting of noncrystalline layers and their random stacks are synthesized, the nanosheets can be obtained by efficient exfoliation.…”

Water-Soluble Metalated Covalent Organic Nanobelts with Improved Bioavailability for Protein Transportation

“…Direct exfoliation of aromatic COFs using mechanical forces (e.g. grinding 11 and ball milling 12 ) in solid state or liquid-based ultra-sonication 13 – 15 is the commonly used strategy, while such treated CONs are poorly dispersed in aqueous solution if without functional decoration. To render COFs hydrophilic, ionization of main backbones has been proposed, and the charged frameworks favor either the self-exfoliation 16 or interfacial evolution 17 into layered CONs.…”