Confined Synthesis of Two-Dimensional Covalent Organic Framework Thin Films within Superspreading Water Layer

Abstract

The confined synthesis of two-dimensional covalent organic framework (2D COF) thin films was developed by using thin superspreading water on the hydrogel immersed under oil as reactor. Through loading two monomers into oil and hydrogel, respectively, COF thin films are synthesized at the oil/water/hydrogel interface. This strategy provides a new way for synthesis of freestanding 2D COF thin films. Detailed characterizations of the COF thin films reveal homogeneous topography, large area, controllable thickness from 4 to 150 nm, and crystallinity with certain orientation. Young's modulus of COF film is measured by AFM indentation as 25.9 ± 0.6 GPa, showing good mechanical properties. On the basis of the freestanding COF films, a nanofilter membrane and photoelectrochemical sensors for Ru were successfully developed. Moreover, the strategy was extended to the synthesis of crystalline zeolitic imidazolate framework-8 thin film, which exhibited high application potential.

Acid Exfoliation of Imine‐linked Covalent Organic Frameworks Enables Solution Processing into Crystalline Thin Films

“…This method produces highly crystalline films, with pores sometimes oriented perpendicular to the substrate, but suffers from numerous disadvantages, including difficult scale‐up, lack of generality across substrate types, production of powder products in addition to the film, and the inability to transfer films between supports . The second is interfacial polymerization, in which the monomers or catalyst are dissolved separately in two immiscible solvents such that COF formation occurs at the interface . This strategy provides freestanding films, but thickness control requires significant reoptimization for every network, and films with poor or no crystallinity are often obtained, especially when they are thinner than 50 nm .…”

Recent Advances in Bioinspired Gel Surfaces with Superwettability and Special Adhesion

“…For instance, asymmetric membranes were synthesized for efficient fluid gating. [169] They used the superspreading water layer on an immersed hydrogel surface as a reactor and introduced amine monomers (4,4′,4″-(1,3,5-triazine-2,4,6-triyl)trianiline) and aldehyde monomers (2,5-dihydroxyterethaldehyde) into the PAAm hydrogel and oil phase (tridecane), respectively. [168] This process induced the formation of asymmetric porous structures on the two sides of the as-prepared PAA-g-PVDF membranes.…”

Interfacial Synthesis of a Monolayered Fluorescent Two‐Dimensional Polymer through Dynamic Imine Chemistry

“…In this process, polymerization of monomers takes place directly at the interface of two phases and ends up with mono-or few-layered 2DPs. Several pioneering researches have been conducted by using different reactions such as Schiff base, [40,[43][44][45] [4 + 4] cycloaddition, [41,42,[46][47][48] and Glaser-Hay coupling reaction. [49][50][51] Among these reactions, dynamic imine chemistry at the air/water interface (Langmuir-Blodgett method) [40,44,52,53] has great potential for large-scale production of highly crystalline 2D polymers due to its dynamic self-healing process.…”