Recent Progress in External‐Stimulus‐Responsive 2D Covalent Organic Frameworks

Abstract

Recently, smart 2D covalent organic frameworks (COFs), combining the advantages of both inherent structure features and functional building blocks, have been demonstrated to show reversible changes in conformation, color, and luminescence in response to external stimuli. This review provides a summary on the recent progress of 2D COFs that are responsive to external stimuli such as metal ions, gas molecules, pH values, temperature, electricity, light, etc. Moreover, the responsive mechanisms and design strategies, along with the applications of these stimulus‐responsive 2D COFs in chemical sensors and photoelectronic devices are also discussed. It is believed that this review would provide some guidelines for designing novel single‐/multistimulus‐responsive 2D COFs with controllable responsive behaviors for advanced photoelectronic applications.

Surfactant‐Modulated a Highly Sensitive Fluorescent Probe of Fully Conjugated Covalent Organic Nanosheets for Detecting Copper Ions in Aqueous Solution

“…[ 21,22 ] COFs have shown merits in fluorescence detection owing to not only their porosity with high surface area to capture and sense analytes such as explosives, [ 23,24 ] metal cations, [ 25,26,62 ] anions, [ 27 ] chiral molecules, [ 28 ] hydroxyl radical and other bio‐related substances. [ 29–31,59,60 ] These analytes could diffuse and permeate into the porous COF structure and interact with COF skeletons, repeating units of which could be finely designed with specific binding sites to selectively target analytes. It is noticed that most reported fluorescent COF sensors are only partial/semi conjugated, and hydrophobic without water dispersibility, which may have certain space to further improve.…”

“…[21,22] COFs have shown merits in fluorescence detection owing to not only their porosity with high surface area to capture and sense analytes such as explosives, [23,24] metal cations, [25,26,62] anions, [27] chiral molecules, [28] hydroxyl radical and other bio-related substances. [29][30][31]59,60] These analytes could diffuse and permeate into the porous COF structure and interact with COF skeletons, repeating units of Efficient detection of aqueous copper ions is of high significance for environmental and human health, since copper is involved in potent redox activity in physiological and pathological processes. Covalent organic frameworks (COFs) have shown advantages in efficient capturing and detecting of copper ions due to their large surface area, robust chemical stability, and high sensitivity, but most of them are hydrophobic, leading to the limitation in sensing copper ions in aqueous media.…”

Process of metal–organic framework (MOF)/covalent–organic framework (COF) hybrids-based derivatives and their applications on energy transfer and storage

“…Recently, COFs constructed using rigid aromatic molecules as building blocks 144 have often been applied as precursors or templates for the construction of efficient electrocatalysts due to the virtues of their diverse synthesis methods, low density, high surface area, high thermal and chemical stability, and easy functionalization. 145 Employing COFs as precursors can facilitate better control over the N dopant density, thus generating more kinds of N species. The calcination of COFs offers a promising strategy to tailor the structures of heteroatom-doped carbon materials and improves their catalytic activities.…”

Smart Two‐Dimensional Membranes for Molecular Separations

“…Porous crystalline frameworks with regular and well-defined arrays would provide a new opportunity to create novel stimuliresponsive materials because crystallinity makes energy transfer between responsive sites and external-stimuli much faster and more efficient, while pores provide reasonable flexibility for structural transformation. [30] MOFs are crystalline porous materials constructed by coordination bonds between metal ions or clusters and organic linkers (typically carboxylate ligands). Therefore, MOFs offer great structural diversities, high porosities, tenable pore geometries, and diverse chemical functionalities.…”