Preparation of a novel hollow-shaped carboxyl-functionalized microporous organic network for efficient solid-phase...

Accurate quantification of indoleamines such as melatonin in complex food matrices is crucial for identifying rich dietary sources and developing potential adjuvant therapies. In this study, a novel hollow-structured, hydrophilic carboxyl-functionalized microporous organic network (H-MON-2COOH) was designed and synthesized via a sacrificial-template approach for the efficient solid-phase extraction (SPE) and determination of three typical indoleamines in fruit juice samples. The material exhibits a high surface area, excellent stability, and robust mechanical strength, along with abundant interaction sites enabling π-π stacking, hydrogen bonding, and electrostatic interactions for indoleamines. These properties collectively facilitate highly selective and sensitive analysis, demonstrated by wide linear ranges (0.9-1000 μg L^-1), low limits of detection (0.3-0.8 μg L^-1), high enhancement factors (94.7-96.2), satisfactory precision (RSDs < 6.5 %), excellent reusability (> 50 cycles), and outstanding chemical stability. The hollow architecture significantly improves mass transfer, leading to rapid adsorption equilibrium. Compared to commercial adsorbents including C18, activated carbon, and HLB, H-MON-2COOH showed superior extraction recovery. This study underscores the promising application of functionalized hollow MONs in sample pretreatment and food analysis.