Stability and Phase Transitions of Nontoxic γ-Cyclodextrin-K+ Metal-Organic Framework in Various Solvents

Abstract

Cyclodextrin (CD) has been used to prepare biocompatible and nontoxic metal-organic frameworks (MOFs) suitable for biomedical applications as drug carriers. In this study, γ-CD/K-based MOF (γ-CD-MOF-1-α) was synthesized and its stability in various solvents was explored by single-crystal X-ray diffractometry (SCXRD) and powder X-ray diffractometry (PXRD). As a result of solvent-induced phase transformations, two novel crystalline phases of γ-CD-MOF-1 were discovered. The newly formed ε- and δ-phases crystallize in orthorhombic and tetragonal symmetry, respectively. In ε-phase, toluene was determined as a guest molecule by SCXRD. Interactions between γ-cyclodextrin and solvent molecules in ε-phase were evaluated using Hirshfeld surface analysis. The thermal stability of the new crystal forms of γ-CD-MOF-1 was analyzed by differential scanning calorimetry and thermogravimetric analysis.

Rapid temperature-assisted synthesis of nanoporous γ-cyclodextrin-based metal–organic framework for selective CO2 adsorption

“…-cyclodextrin (-CD) is a symmetrical cyclic oligosaccharide that is massproduced enzymatically from starch and comprised of eight asymmetric a-1,4-linked dglucopyranosyl residues. Advantageously, -CD-MOF non-toxicity and biocompatibility features offer a unique opportunity to use in a variety of applications like gas adsorption and separation [27]. For instance, Yan et al [28] utilized thermogravimetric approach to study the adsorption and desorption of CO2 over CD-MOF.…”

Never-Ending Story: New Cyclodextrin-Based Metal–Organic Framework Crystal Structures Obtained Using Different Crystallization Methods

“…Therefore, we think that compound 5 structure could be very similar to those compounds’ molecule arrangements because it is identical to the structure arrangement in the γ-CD moiety (see Figure ). The cell parameters and space groups are different: P 42 1 2 (SIBJES, SIBJAO, and NUNRIX) and I 4 (ZUGDIR) . As can be seen from Figure , the γ-CD rings’ arrangement is practically the same in downward view c and slightly shifted (ZUGDIR cases) in one line in the view down direction a .…”

“…We also obtained the γ-CD-K α phase in the drying process using elevated temperatures. Products formed in the reaction with potassium carbonate gave the γ-CD-K (ZUGDIR) phase after the drying process (obtaining the product in a solvent exchange process, whose characterization was described in our previous research) . The reaction with NaOH gave already known phases, YAPROY.…”

“…Moreover, γ-CD-K exhibits multiple crystal phases, including the trigonal β phase (LAJLAL02), which crystallizes in space groups R 32, ε (orthorhombic, I 222), and δ (tetragonal, I 4) . The isomorphism extends to γ-CD-Cs (YAPRUE) and γ-CD-K (ZUGDIR) δ phases. In the monoclinic crystal system, β-CD-K (KOBRIC) and β-CD-Na (PULLOZ) similarly exhibit isomorphism, occupying the space group P 2 1 .…”

“…LAJLAL is isomorphic with γ-CD-Rb (LAJLEP) and γ-CD-Cs (LAJKULE). Moreover, γ-CD-K exhibits multiple crystal phases, including the trigonal β phase (LAJLAL02), which crystallizes in space groups R 32, ε (orthorhombic, I 222), and δ (tetragonal, I 4) . The isomorphism extends to γ-CD-Cs (YAPRUE) and γ-CD-K (ZUGDIR) δ phases.…”