Chitosan bead containing metal–organic framework encapsulated heteropolyacid as an efficient catalyst for cascade condensation reaction

Abstract

Using cyclodextrin and chitosan that are bio-based compounds, a novel bi-functional catalytic composite is designed, in which metal–organic framework encapsulated phosphomolybdic acid was incorporated in a dual chitosan-cyclodextrin nanosponge bead. The composite was characterized via XRD, TGA, ICP, BET, NH3-TPD, FTIR, FE-SEM/EDS, elemental mapping analysis and its catalytic activity was examined in alcohol oxidation and cascade alcohol oxidation–Knoevenagel condensation reaction. It was found that the designed catalyst that possess both acidic feature and redox potential could promote both reactions in aqueous media at 55 °C and various substrates with different electronic features could tolerate the aforementioned reactions to furnish the products in 75–95% yield. Furthermore, the catalyst could be readily recovered and recycled for five runs with slight loss of the catalytic activity. Notably, in this composite the synergism between the components led to high catalytic activity, which was superior to each component. In fact, the amino groups on the chitosan served as catalysts, while cyclodextrin nanosponge mainly acted as a phase transfer agent. Moreover, measurement of phosphomolybdic acid leaching showed that its incorporation in metal–organic framework and bead structure could suppress its leaching, which is considered a drawback for this compound. Other merits of this bi-functional catalyst were its simplicity, use of bio-based compounds and true catalysis, which was proved via hot filtration.

One-pot synthesis of 2,5-diformylfuran from fructose using a bifunctional catalyst derived from phosphomolybdic acid and chitosan

“…2a that the carbon material derived from chitosan revealed a broad peak centered around 20 to 30° in the 2θ range, indicating the presence of an amorphous carbon structure (Kalaiselvimary and Prabhu 2019;Kong et al 2012). The peak corresponding to chitosan at 25º exhibited reduced intensity and shifted towards 30° in the XRD spectrum of the PMAC samples, suggesting that the introduction of PMA influenced the arrangement of carbon atoms (Tong et al 2017: Yu et al 2014Sadjadi et al 2023). Moreover, the distinguished peaks at 2θ values of ~10º and ~25º were only present in PMAC samples indicating the existence of PMA (Ahmadian and Anbia 2023).…”

Sulfonic acid-functionalized chitosan–metal–organic framework composite for efficient and rapid conversion of fructose to 5-hydroxymethylfurfural

“…As CS surface is rich in functional groups, it can be readily functionalized or incorporated into the structure of composites in covalent and non-covalent approaches. As an instance, CS has been conjugated with MOFs to furnish composite 41 , which benefits from the characteristics of both CS and MOFs, which are porous crystalline materials with tunable porosity 42 – 44 . Interestingly, the acidic features of both CS and MOF can be adjusted by several approaches, such as functionalization 45 , 46 .…”

Dual-drug (Curcumin/Ciprofloxacin) loading and release from chitosan-based hydrogels embedded with magnetic Montmorillonite/Hyaluronic acid for enhancing wound healing

“…Over recent years, the mixture of two or more different polymers to produce hydrogels has been investigated because of their specific properties. Among the desired materials are the chitosan and hyaluronic acid blending with its unique features [ 23 , 24 ]. As there is glycosaminoglycans in the cartilage structure which, chitosan has many structural similarities with glycosaminoglycans; therefore, chitosan can be exploited in cartilage tissue engineering [ 25 , 26 ].…”