Roles of\nBrønsted-Base and Brønsted-Acid\nCatalysts for Glucose Isomerization into Fructose and Fructose Dehydration\ninto 5‑Hydroxymethylfurfural

5-Hydroxymethylfurfural (5-HMF) holds\nsubstantial importance\nas\na foundational chemical that can be potentially transformed into biofuels\nand various additional high-value products. Fructose is gaining popularity\nas one of the raw materials for the facile formation of 5-HMF. However,\nit is not as abundant in nature as glucose, the primary product derived\nfrom biomass breakdown and the most abundant monosaccharide globally.\nProducing fructose through glucose isomerization is an economical\napproach in this context. This study investigates several types of\nnovel, facile, and reusable hydrogel catalysts for the isomerization\nof glucose into fructose and dehydration of fructose into 5-HMF in\ngreen solvent media. This study marks the first application of both\namine and amide functional groups within a single catalyst (PEGDA-DMAPMA)\nfor glucose isomerization. The results of glucose isomerization using\nBrønsted-base PEGDA-DMAPMA hydrogel catalysts reveal a 45% glucose\nconversion rate and a 27% fructose yield, with a 61% selectivity at\n110 °C, within a 2 h reaction time. Brønsted-acid PEGDA-3SMP-H\ngave a fructose conversion rate of 93%, yielding 65% 5-HMF at 120\n°C after 6 h. A significant observation was made for PEGDA-3SMP-H,\nindicating an increase in the catalytic ability with regeneration\ncycles. The synthesized catalysts PEGDA-DMAPMA and PEGDA-3SMP-H exhibited\nstability up to 120 °C despite an increase in swelling ratio\nat higher temperatures and times. Furthermore, PEGDA-3SMP-Cu<sup>2+</sup> demonstrated a considerable yield of fructose compared to other\nmetal ion-modified Brønsted-acid catalysts. Additionally, an\nefficient heating method for this process was identified. In conclusion,\nthe prepared hydrogel catalysts are preferred for industrial applications\nin carbohydrate conversion.