High-efficiency adsorption of caffeine and nicotine in aqueous phases by functionalized MIL-101 nanostructures: experimental and density functional theory study

초록

MIL-101, a metal–organic framework, is highly effective at adsorbing nitrogen-containing compounds due to its exceptional structural properties. Herein, pristine and functionalized MIL-101s with amino (–NH2) and carboxyl (–COOH) groups were synthesized via a hydrothermal method to remove caffeine (CAF) and nicotine (NIC), two common water pollutants from coffee and tobacco. The resulting nanoadsorbents exhibited high crystallinity, excellent thermal stability, large surface area, and superior regeneration capability. Adsorption followed pseudo-second-order kinetics and the Langmuir isotherm model, indicating efficient monolayer adsorption. Among the materials, COOH-functionalized MIL-101 demonstrated the best performance, achieving near-complete removal of CAF (99.8 %, 374.3 mg/g) and NIC (95.1 %, 356.5 mg/g) at pH 7.0 and 308 K. Its maximum adsorption capacities, based on the Langmuir model, were 442.1 mg/g for CAF and 350.3 mg/g for NIC at 25 °C, with surface coverages of 32.2 % and 30.8 %, respectively. Thermodynamic studies revealed an endothermic and spontaneous process involving both physisorption and chemisorption. Density functional theory and natural bond orbital analyses further confirmed that COOH-ligand provided the highest adsorption energy, shortest C–C interaction distance, and greatest electron difference, primarily through hydrogen bonding and electrostatic interactions. These findings establish COOH-MIL-101 as a highly efficient and regenerable adsorbent for water purification. © 2025 The Korean Society of Industrial and Engineering Chemistry

키워드