MOF traps molecules that gum up bioethanol production

A porous metal-organic framework sorbent could boost the efficiency of ethanol production from cellulosic biomass by trapping compounds that inhibit fermentation, according to a study (Chem. Commun. 2016, DOI: 10.1039/c6cc05864g).

Woody plants and grasses hold enormous supplies of cellulose, from which ethanol can be produced via fermentation of sugars extracted from the plant materials. This route to ethanol production currently generates hundreds of millions of liters of the renewable fuel annually, a value that is expected to climb.

Extracting the sugars from biomass requires breaking down the plant material, which is notoriously recalcitrant. Biofuel manufacturers typically rely on harsh acid treatments to do that job. The process works well, but it generates aqueous sugar solutions contaminated with 5-hydroxymethylfurfural (HMF) and other furanics. Those compounds are toxic to the organisms that do the fermentation and thereby limit the process efficiency. They are also tough to separate from sugar solutions: Sorbents that trap the harmful franics also tend to trap valuable sugars.

A team led by Alexander Katz of the University of California, Berkeley, may have come up with a way to overcome the separations problem. The group finds that NU-1000, a metal-organic framework compound featuring pyrene linkers, selectively traps furanics and leaves sugars alone. For example, in tests in which the glucose concentration was 300 times as great as that of HMF, NU-1000 trapped 80% of the HMF but no detectable quantity of glucose.