Glass catalysis shatters material’s inert reputation

Beakers, flasks, petri dishes—glassware is a hallmark of chemistry labs. Though commonly thought of as inert, glass containers are known to affect certain chemical reactions, but researchers have not understood exactly how or to what extent. Now, a team reports that glass beads can catalyze many base-catalyzed reactions, suggesting that glass could be used as a green catalyst in place of toxic or expensive chemicals (Chem. Science, 2021, DOI: 10.1039/d1sc02708e)

Late last year, Yangjie Li of Graham Cooks’s lab at Purdue University published work based on an accidental discovery that an amine transfer reaction proceeded faster in glassware than in plastic, and that adding glass beads accelerated reactions even further (Angew. Chem., Int. Ed. 2020, DOI: 10.1002/anie.202014613). Li wanted to find out more.

Li and colleagues tested thousands of reaction conditions and dozens of reactions to see how the presence of glass microspheres affected various reaction types. “We found that there are so many base-catalyzed reactions that can be catalyzed by just adding these glass particles in the solution”—as opposed to the expensive, caustic basic chemicals typically used for these kinds of reactions, she says. Glass beads accelerated elimination, solvolysis, condensation, and oxidation reactions 30- to 2,000-fold.

The surface of glass is covered with dissociable silanol groups, giving it a negative charge when in contact with solution. The researchers determined that this allows glass to act as a strong base while producing nucleophilic solvent anions that catalyze reactions.

“The second very important part of [the study] is that we found that glass can degrade biomolecules such as lipids,” Li says. “So it could be a huge impact in bioanalytical work and in clinical settings.”

Cooks says that for standard concentrated solutions stored in a glass container, “there’s no problem at all” because “99.9% of the material will not make it to the surface.” But he adds that for specialty low-concentration ingredients or analytical tests at low concentrations, “we found significant loss of the material.”

“I think it is an outstanding new direction,” says Richard Zare, a physical and analytical chemist at Stanford University who was not part of the study. Zare is interested in how this can be scaled up as a practical means of making new chemicals.