Facile Synthesis of Cu-Based Metal-Organic Framework/Chitosan Composite Granules as Adsorbents

The <i>in situ</i> synthesis of metal–organic framework crystals incorporated into natural polymers is an efficient approach to manufacturing adsorbents of large size, which is convenient in terms of adsorbent handling, operating, and transportation for practical adsorption processes. Herein, CuBTC/CS (BTC = 1,3,5-benzenetricarboxylate; CS = chitosan) composite granules were successfully prepared by dispersing Cu²⁺ ions into the CS matrix before generating Cu²⁺/CS composite beads, which subsequently grew into CuBTC crystals incorporated in the CS network. To evaluate their quality, the characteristics of the prepared composites were systematically analyzed, which were observed to be controlled by the amount of Cu²⁺ ions present in the reaction system. The highest quality material was utilized as an adsorbent for toluene uptake, which was estimated via breakthrough data. The adsorptive interaction was investigated by determining the heat of adsorption, whilst the kinetic behavior of the adsorption process was described by pseudo-first-order and pseudo-second-order models. Additionally, the mechanism of diffusion of toluene molecules into the granular adsorbent was examined in detail. Finally, to predict the adsorption behavior via the mathematical models of Yan and Thomas, the experimental breakthrough data were utilized. The herein-developed route allows granular adsorbents to be manufactured in large quantities and used in the practical volatile organic compound adsorption.