Adsorption Behavior of Aromatic Carboxylic Acids on A Cyclodextrin-Based Metal-Organic Framework

Abstract

A cyclodextrin-based metal-organic framework (CD-MOF) was crystallized by methanol vapor diffusion. The performance of CD-MOF was compared with commercial available adsorbents (faujasite zeolite, activated carbon and activated clay) for the adsorption of ferulic acid at 298 K in methanol. The adsorption behavior of aromatic carboxylic acids on the CD-MOF was also investigated. The initial adsorption rate of ferulic acid in methanol on the CD-MOF was lower than that for activating carbon and faujasite zeolite, due to the alternating passage of ferulic acid through hydrophilic pore and hydrophobic pore in CD-MOF. The saturated adsorption amount on the CD-MOF was highest among those on the other adsorbents. The high adsorption amount was obtained for aromatic carboxylic acids with high values of pKa(W). A single saturation state of benzoic acid on the CD-MOF was obtained at a concentration of more than 1.0 mmol/L. The molar ratio of benzoic acid to the (γ-CD)6 unit was evaluated to be 4.4 from the saturated adsorption amount.
 Keywords: Adsorption, Aromatic Carboxylic Acid, Cyclodextrin, Porous Crystal, Adsorbent