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The NU-1000 metal-organic framework (MOF), a versatile mesoporous material, has unexpected recognition abilities. Recently, a synergistic theoretical and experimental effort demonstrated how NU-1000, a water-stable MOF, can selectively discriminate sugars from an aqueous solution based on their specific interactions. This work resulted from a collaboration between the groups of professors Alexander Katz, University of California, Berkeley, Omar K. Farha, Northwestern University, and Laura Gagliardi at the University of Minnesota. The theoretical study was performed by Varinia Bernales, Ph.D., a post-doctoral research associate in the Gagliardi group, and was recently published in Chemical Communication.
The major achievement was the discovery that the adsorption processes of glucose and cellobiose on the NU-1000 MOF occur at the hydrophobic sites, whereas the hydrophilic groups are not involved. The understanding of these phenomena at the molecular level unraveled the role of the framework and the interactions responsible for selective carbohydrate molecular recognition. Until now, only enzymes have demonstrated the ability to selectively bond the β-linked dimer of glucose, cellobiose, while completely rejecting the bonding of glucose itself. Electronic structure calculations have shown that the key of this selective molecular recognition is the number of favorable CH–π non-covalent interactions between the sugar and the aromatic organic linkers of the MOF. The results highlight the importance of MOF environment and uniformity when adsorbing sugars, and motivate future work exploring new frontiers on selective catalytic conversion of biomass in MOFs.
This work was supported by the Inorganometallic Catalyst Design Center (ICDC), an Energy Frontier Research Center based at the University of Minnesota, funded by the Department of Energy.
Schematic Illustration of the “ON-OFF Selective Recognition of Sugar on NU-1000.”
