(682b) Selective Carbohydrate Adsorption in Solvated Nu-1000

As the efforts for green chemistry and sustainability continue to grow, production of biofuels becomes more important. During the production of bioethanol, cellulose-based feedstocks are sent through physicochemical pretreatments to enhance the amount of extractable sugar per biomass processed. The drawback of the pretreatment process is that besides obtaining sugar, furanic species, 5-hydroxymethylfurfural (HMF) and furfural, are also formed as a result of side reactions. The selective removal of these furanic compounds is crucial since HMF and furfural have inhibiting effects on fermentation and effective separation of them will allow more economical production of cellulosic ethanol.

Metal-organic frameworks (MOFs) can provide solutions to many separation problems due to their ordered, highly porous, chemically versatile structures. MOFs are comprised of metal nodes and organic linkers and considering various organic linkers and metal types that can be selected, it is possible to create structures which can have favorable interactions for a particular species and an unfavorable interaction for another species. For the selective capture of furanic species over sugars (glucose, fructose, xylose), NU-1000, a Zr-based MOF, has been experimentally shown to have almost infinite selectivity in aqueous-phase.¹

The aim of this computational study is to elucidate the reasons behind why NU-1000 can specifically adsorb some carbohydrates (HMF, furfural) but not others (glucose, fructose, xylose). To have a fundamental understanding about this highly selective separation, classical molecular dynamics (MD) simulations are employed to calculate relative free binding energies where solvation effects are considered. Using MD results, the high adsorption selectivity for furanic compounds over sugars will be explained by describing the interaction characteristics of compounds in NU-1000.

References 1. Yabushita, M. et al. Complete furanics-sugar separations with metal-organic framework NU-1000. Chem. Commun. 52, 11791–11794 (2016).