Electroactive Covalent Organic Frameworks/Carbon Nanotubes Composites for Electrochemical Sensing

Abstract

An electroactive covalent organic framework (COF Thi−TFPB ) was prepared by a dehydration condensation reaction between 1,3,5-tris(p-formylphenyl)benzene (TFPB) and thionine (Thi) and wound with carbon nanotubes (CNTs) to design COF Thi−TFPB −CNT composites for electrochemical sensing of ascorbic acid (AA) and pH. COF Thi−TFPB was a highly ordered two-dimensional (2D) crystalline nanosheet, and its thickness was 0.75 nm. The loading of CNTs onto COF Thi−TFPB nanosheets could significantly improve the dispersibility, stability, and catalytic activity of the CNTs. Here CNTs could well catalyze the oxidation of AA, while COF Thi−TFPB had a pair of redox peaks that were inert for AA. Accordingly, a ratiometric electrochemical AA sensor was constructed by using the peak of COF Thi−TFPB as the reference signal. The ratiometric AA sensor showed a detection limit of 17.68 μM and linear ranges of 53.04 μM to 4.00 mM and 4.00−8.00 mM, revealing a good performance, together with satisfactory selectivity, reproducibility, and stability. The redox peak potential of COF Thi−TFPB was linearly shifted with the pH, so a pH sensor was constructed. The linear range and sensitivity of the pH sensor were 1−12 and 54 mV pH −1 , respectively. The electroactive COF Thi−TFPB −CNT might also be applied to construct other electrochemical sensors.

A New Squaraine‐Linked Triazinyl‐Based Covalent Organic Frameworks: Preparation, Characterization and Application for Sensitive and Selective Determination of Fe3+ Cations

“…COFs are linked by strong covalent bonds, such as B−O, C=N, C−N, B−N, and N=N bond linkages, which make them more stable and lower in density. Due to their remarkable properties, COFs present the potential in many specific functional applications, including gas storage and separation,[4] heterogeneous catalyst, photocatalysis, dye adsorption, optoelectricity, fluorescence detection, drug delivery, separation analysis, electric analysis, power storage, detection and adsorption of radioactive substances, and so on. At present, there are more and more functional COFs about fluorescence detection were reported.…”

Electrochemical Sensors Based on Covalent Organic Frameworks: A Critical Review

“…An electroactive 2D COF Thi−TFPB nanosheet packaged on amino-functionalized CNT was designed as a ratiometric electrochemical AA sensor, showing satisfactory selectivity, reproducibility, and stability (Wang L. et al, 2020 ). The COF Thi−TFPB was synthesized by a dehydration condensation reaction between 1,3,5-tris (p-formylphenyl) benzene (TFPB) and thionine (Thi) and this porous crystalline material was a highly ordered 2D nanosheet.…”

“…Wang reported an electroactive COF with multiple redox-active states synthesized by an amine-aldehyde condensation reaction between 4, 4′,4″-(1,3,5-triazine-2,4,6-triyl) trianiline and 2,5-dihydroxy terethaldehyde (COF DHTA−TTA ), which was applied for the construction of a ratiometric electrochemical sensor for the detection of hydrogen peroxide and pH level based on both current and potential signals (Xu M. et al, 2019 ). An electroactive COFs composite was also prepared by a dehydration condensation reaction between 1,3,5-tris(p-formylphenyl) benzene (TFPB) and thionine (Thi) wound with carbon nanotubes (CNT) to construct the ratiometric electrochemical sensing of ascorbic acid (Wang L. et al, 2020 ).…”

Covalent Organic Framework Composites: Synthesis and Analytical Applications

“…CNTs can be either single-walled (SWNTs) or multi-walled nanotubes (MWNTs), which notably affects their mechanical properties [ 49 ]. An electroactive COF assembled from 1,3,5-tris( p -formylphenyl)benzene (TFPB) and thionine (Thi) was capped with amino-functionalized carbon nanotubes (CNTs) to form COF Thi - TFPB -CNT composites for sensing [ 55 ]. The composite was prepared by simply subjecting the CNTs to the solvothermal COF growth conditions.…”

“…However, the poor inherent electrical conductivity of COFs remains a pitfall in their further application in electrochemistry. Thus, COFs have been successfully combined with highly conductive materials, such as noble metal nanoparticles [ 67 , 136 , 137 , 138 ], magnetite nanoparticles [ 38 , 139 ], graphene oxide [ 140 ], carbon nanotubes [ 55 , 141 ], or conductive polymers [ 142 ], to increase their functionality and broaden their electrochemical applications.…”