Room-temperature synthesis of a microporous organic network followed by integration with magnetic MWCNTs for sensitive electrochemical detection of caffeic acid in fruit samples

A novel MON effectively integrates with magnetic MWCNT to construct MMWCNT@MON(MMON). • The MMON/MMWCNT int-ext hybrid exhibits substantial synergistic effects. • MMON/MMWCNT magnetically immobilized on the MGCE renders favorably stable signals. • MMON/MMWCNT@MGCE exhibits high CA sensitivity and low LOD. • The sensor successfully detected CA levels in various fruits with satisfactory recovery. Caffeic acid (CA) is a phenolic compound widely distributed in plants, possessing anti-inflammatory and antioxidant activities, yet it is also associated with potential carcinogenic risks. Therefore, developing a simple and sensitive electrochemical sensor for CA detection is of great significance. In this work, a novel magnetic sensor was fabricated for the first time by combining a room-temperature-synthesized microporous organic network (MON) with magnetic MWCNTs, and the magnetic property of the composite was utilized in conjunction with a magnetic glassy carbon electrode (MGCE) to achieve a binder-free and robust assembly. The sensor was employed for highly sensitive detection of CA, achieving an ultrahigh sensitivity of 124.9 μA μM −1  cm −2 . The composite exhibited remarkable synergistic effects: MMWCNTs provided structural support, magnetism, and signal amplification, while MMON (472.48 m 2  g −1 , 160.5 Ω) demonstrated superior conductivity compared to pure MON (493.44 m 2  g −1 , 409.7 Ω) while retaining a high specific surface area. The sensor displayed excellent electrocatalytic performance toward CA, with a wide linear range of 0.05–10 μM, a detection limit of 3.98 nM (S/N = 3), and satisfactory reproducibility, selectivity, and stability. Real-sample analysis of freshly squeezed juices from apples, blueberries, grapes, and tomatoes via the standard addition method, validated by UV–Vis spectrophotometry, yielded recoveries ranging from 94.9% to 102.8%, demonstrating satisfactory results. Compared to traditional sensors, this sensor offers significant advancements in preparation time, economic efficiency, and sensing performance, demonstrating great potential for rapid and sensitive detection in the food industry. Download: Download high-res image (98KB) Download: Download full-size image