Structural Isomerism of Covalent Organic Frameworks Causing Different Electrochemiluminescence Effects and Its Application for the Detection of Arsenic

Abstract

The structural isomerism of the covalent organic framework (COF) has a significant effect on the electrochemiluminescence (ECL) performance. Herein, we report a pair of isomeric COFs, (TFPB-BD(OMe) 2 -H and TAPB-BD(OMe) 2 -H), based on the different directions of imine linkages and further conversion of the imine to the quinoline structure. The obtained two isomeric COFs with the same composition and similar structures exhibit dramatic differences in the photoelectrochemical and ECL fields. Indeed, TFPB-BD(OMe) 2 -H demonstrates robust ECL emission superior to that of TAPB-BD(OMe) 2 -H. The difference in ECL performance is due to the stronger polar interaction of TFPB-BD(OMe) 2 -H than that of TAPB-BD(OMe) 2 -H. The polarity is derived from the uneven charge distribution within the framework and enhances the electron interactions. In addition, the ordered conjugate skeleton provides high-speed charge transport channels for carrier transport. Therefore, the TFPB-BD(OMe) 2 -H presents a smaller band gap energy and stronger polarization interaction, which are more favorable to charge migration to achieve stronger ECL signals. Furthermore, we describe a convenient ECL sensor for detecting toxic As(V) with an outstanding detection property and ultralow detection limit. This work provides a guiding principle for the design and development of ECL organic luminophores.

σ-Hole Effect-Induced Electroluminescence of Halogen Cocrystals for Determination of Iodide in Seawater

“…As observed by Figure c,d, the ECL intensity of the TFTI-TMT/GCE system gradually descended with iodide ion concentration increasing from 10 to 5000 nM, and a good linear correlation appeared with iodide ion concentration ( R 2 = 0.999). Utilizing the formula LOD = 3σ/ k to calculate the limit of detection, where k is the slope of the linear equation and σ is the standard variance, the LOD was 3 nM, which was far below the national limit for iodine in drinking water (10 ppb) and the detection methods reported so far (Table S2), indicating that the TFTI-TMT/GCE monitoring platform was superior in sensitivity. Finally, five independent experiments were conducted to verify the reproducibility of the ECL sensor for iodide detection, and Figure S22 manifests that this analytical method is stable and repeatable.…”

Regioisomerism in Thienothiophene-Based Covalent Organic Frameworks─A Tool for Band-Gap Engineering

“…Constitutional isomerism of COFs has mainly been applied by alternating the functional groups (e.g., amines and aldehydes) on the building blocks − or by changing the potential orientations of the monomer units in the lattice relative to each other (e.g., functional groups in the axial or equatorial positions) . Recently, an alternative method for constitutional isomerism was introduced by choosing positionally isomeric benzobisoxazoles as COF building blocks in olefin-linked COFs prior to COF formation.…”