High adsorption selectivity, capacity and rate of fructose using metal–organic frameworks with abundant zirconium open metal sites

Abstract

Fructose is an essential raw material for the biorefinery industry and can be produced from glucose via catalytic isomerization; however, efficient separation to obtain high-purity fructose from glucose/fructose mixed solution remains a challenge. In this study, MOF-808 with a 6-connected Zr₆ node was employed as an adsorbent, and its adsorption and separation performances for fructose and glucose were investigated. MOF-808, whose pore size is 1.42 nm, exhibited a high adsorption selectivity factor of 17.8 for fructose. The adsorption process reached equilibrium within 5 h, and the adsorption capacity reached 362 mg g⁻¹. We propose that the larger pore size MOF-808 exhibited higher selectivity for fructose than the previously reported NU-906 (1 nm) due to the increase in the number of zirconium (Zr) open metal sites, enhancing the selectivity of the pore environment and consequently expelling glucose from the pore. This hypothesis was verified by the adsorption selectivity of fructose and glucose in various defect concentrations of UiO-66, which acted as a tunable framework. In addition, the column packed with MOF-808 showed excellent performance, with an adsorption selectivity of 5.0 in the breakthrough experiment. This study demonstrated that MOF-808 with abundant Zr open metal sites could efficiently separate glucose and fructose, which can inspire the design of adsorbents for fructose purification.