Covalent Organic Polymers and Frameworks for Fluorescence-Based Sensors

Abstract

Following the advancements and diversification in synthetic strategies for porous covalent materials in the literature, the materials science community started to investigate the performance of covalent organic polymers (COPs) and covalent organic frameworks (COFs) in applications that require large surface areas for interaction with other molecules, chemical stability, and insolubility. Sensorics is an area where COPs and COFs have demonstrated immense potential and achieved high levels of sensitivity and selectivity on account of their tunable structures. In this review, we focus on those covalent polymeric systems that use fluorescence spectroscopy as a method of detection. After briefly reviewing the physical basis of fluorescencebased sensors, we delve into various kinds of analytes that have been explored with COPs and COFs, namely, heavy metal ions, explosives, biological molecules, amines, pH, volatile organic compounds and solvents, iodine, enantiomers, gases, and anions. Throughout this work, we discuss the mechanisms involved in each sensing application and aim to quantify the potency of the discussed sensors by providing limits of detection and quenching constants when available. This review concludes with a summary of the surveyed literature and raises a few concerns that should be addressed in the future development of COP and COF fluorescencebased sensors.

Inter- and Intra-Hydrogen Bonding Strategy to Control the Fluorescence of Acylhydrazone-Based Conjugated Microporous Polymers and Their Application to Nitroaromatics Detection

“…Generally, NACs have an electron-deficient planar benzene ring due to the presence of a nitro (NO2) group and can easily form a donor−acceptor complex with an electronrich aromatic substance [40]. During complexation, the PL in electron-donor aromatic groups is quenched because an electron in the excited state moves to the π*-orbital of the NACs instead of to the ground state of the donor molecules [41]. BH-CMP and ABH- Generally, NACs have an electron-deficient planar benzene ring due to the presence of a nitro (NO 2 ) group and can easily form a donor-acceptor complex with an electron-rich aromatic substance [40].…”

Porous organic polymers as a platform for sensing applications

“…† Currently, several review articles on POPs from different perspectives have been published, [10][11][12][13][14] but those related to the sensing applications of POPs are very rare. [15][16][17][18] They either just focused on COF materials, 16 or only on their fluorescence-based sensing, 15,17 or on their photoluminescence. 18 There are few reviews to give comprehensive overviews of different kinds of POPs using as different sensors.…”

Following the light: 3D-printed COF@poly(2-hydroxyethyl methacrylate) dual emissive composite with response to polarity and acidity

“…The dynamic nature of the covalent bonds formed during the synthesis enables self-healing and error correction of the structures and is a key factor determining the high crystallinity exhibited by these materials. 2–7 The intrinsic porosity, crystallinity, and chemical stability exhibited by COFs, together with the incorporation of appropriate functional groups, make these materials very attractive in a wide range of applications, including gas storage and separation, 8 renewable energy applications, 9 development of lithium batteries, 10 environmental remediation, 11,12 catalysis, 13 fluorescence and colorimetric based sensing 14–17 and development of light-emitting materials. 18,19…”

“…21,22 An important drawback of the majority of COF-based chemical sensors reported to date is that, in fact, they are used in solvent suspensions, which limits their use in day-to-day applications. 14…”