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.

中文翻译：

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用于电化学传感的电活性共价有机骨架/碳纳米管复合材料

通过1,3,5-三（对-甲酰基苯基）苯（TFPB）与硫氨酸（Thi）的脱水缩合反应制备电活性共价有机骨架（COF _Thi–TFPB），并用碳纳米管（CNTs）缠绕设计COF _Thi–TFPB –CNT复合材料用于电化学检测抗坏血酸（AA）和pH。COF _Thi–TFPB是一种高度有序的二维（2D）晶体纳米片，其厚度为0.75 nm。将碳纳米管负载到COF _Thi–TFPB纳米片上可以显着改善碳纳米管的分散性，稳定性和催化活性。碳纳米管可以很好地催化AA的氧化，而COF _Thi–TFPB有一对对AA呈惰性的氧化还原峰。因此，通过使用COF _Thi–TFPB的峰作为参考信号构建了比例电化学AA传感器。比例式AA传感器的检测限为17.68μM，线性范围为53.04μM至4.00 mM和4.00–8.00 mM，显示出良好的性能，以及令人满意的选择性，重现性和稳定性。COF _Thi–TFPB的氧化还原峰电位随pH线性变化，因此构建了pH传感器。pH传感器的线性范围和灵敏度分别为1–12和54 mV pH ^–1。电活性COF _Thi–TFPB –CNT也可用于构建其他电化学传感器。