Adsorption and detection of caffeine in tea samples by surface active MPN@COFs

Inspired by the surface structure of mussel, a novel bionic adsorbent (MPN@COFs) was prepared using an in situ synthetic strategy for the selective adsorption of caffeine and the physicochemical structure, surface morphology and composition of were characterized by scanning electron microscopy, Fourier-transform infrared spectrometry, X-ray photoelectron spectroscopy. The analytical data showed that the specific surface area of MPN @ COF was as high as 133.62 m2/g, which was stable and adaptable to acid and alkaline environments, with a adsorption rate of 78 %, and still maintained a high adsorption rate after reuse for three times. The adsorption isotherms and adsorption kinetics fit the Langmuir model and the quasi-secondary kinetic model better, respectively. Compared with single COFs and MPN, the adsorption efficiency of MPN@COFs increased by 40.54 % and 57.65 %, respectively. Moreover, the composite material could be reused three times, the HPLC-MS/MS method established in this study has high sensitivity, and this rapid detection technique can provide strong support for the detection of caffeine in beverages and the removal of caffeine from tea and its products.