Researchers tap ancient glassmaking tricks to engineer carbon-trapping glass

At a glance:

• Ancient additives like cobalt and copper created vivid glass hues along the Silk Road millennia ago.
• Modern ZIF-62 glass, made from metal-organic frameworks, can separate CO2 from air at a 34.5:1 ratio.
• Sodium benzimidazolate lowers ZIF-62’s processing temperature from 561°F to 322°F, easing manufacturing.

Old-world chemistry, new-world materials

Precision chemical analysis has revealed that ancient glassmakers across the Silk Road and the Mediterranean were far more sophisticated than previously imagined. As early as the 2nd millennium BCE, cultures from Egypt to Mesopotamia were incorporating metallic additives like cobalt for deep blues and copper for shimmering greens, creating prized trade goods. These ancient techniques, once used to delight Mycenaean elites, are now providing a blueprint for solving a critical 21st-century challenge: manufacturing advanced glass for carbon capture and optics. A team of researchers from the University of Birmingham and TU Dortmund University has discovered that traditional glass modifiers—specifically benzimidazolate compounds—can solve persistent production problems with a novel class of materials called zeolitic imidazolate framework (ZIF) glasses.

These are not the silica-based glasses of antiquity. ZIF glasses blend metal atoms with organic carbon-based molecules, forming intricate crystalline structures riddled with microscopic pores. This unique architecture makes them ideal for trapping greenhouse gases or manipulating light in fiber optics. However, their promise has been hampered by difficult manufacturing. “Glass has been part of human civilisation for millennia,” notes University of Birmingham chemist Dominik Kubicki, a coauthor of the new study. “From ancient Mesopotamia to modern fibre-optic cables, small amounts of chemical modifiers make it easier to process glass and change its functional properties.”

Disrupting the network: A transferable principle

The core insight was to test whether the same principles used to fine-tune conventional silicate glass for thousands of years could be applied to these hybrid metal-organic glasses. “Our approach is inspired by how conventional silicate glasses have been modified: disrupting the network structure to tune melting behaviour and mechanical properties,” explains Sebastian Henke, a chemist at TU Dortmund and collaborator on the project. “Our study shows the same principle can be transferred to hybrid metal-organic glasses.”

The researchers introduced two specific additives: sodium benzimidazolate and lithium benzimidazolate. They tested these on ZIF-62, a zinc-based metal-organic glass already known for its exceptional ability to selectively separate carbon dioxide from nitrogen-rich mixtures—a crucial process for capturing emissions from industrial flues or even directly from air. The baseline selectivity ratio of ZIF-62 stands at an impressive 34.5 to one. The ancient-modifier hack, however, did more than just maintain this selectivity.

Tuning pores and temperatures

The addition of sodium benzimidazolate proved particularly transformative. It increased the total pore volume available for gas adsorption by approximately 26%, suggesting the additive creates more and potentially tunable nano-spaces within the glass structure for CO2 molecules to enter. More significantly for manufacturability, both additives lowered the glass transition temperature—the point at which the material becomes pliable enough to shape. Lithium benzimidazolate provided a modest reduction, but sodium benzimidazolate dramatically dropped the threshold from 561 degrees Fahrenheit (294 degrees Celsius) to 322 degrees Fahrenheit (161 degrees Celsius).

This temperature plunge is a game-changer. “MOF glasses like ZIF-62 usually ‘soften only at high temperatures’ around 300 degrees C (572 degrees F), which is perilously ‘close to their degradation temperature, making manufacturing challenging and limiting broader use,’” Kubicki stated. By pulling the processing temperature well below the degradation point, the ancient additive hack makes ZIF glasses far more compatible with existing industrial glass-forming techniques, potentially paving the way for scalable production.

Parallels to a 1930s glassware revolution

The team draws a direct line between their work and a historic materials breakthrough. They note that their pore-size tuning tests “parallels the well-established Vycor process,” developed in the 1930s by chemist Martin Nordberg at Corning. Vycor glass, renowned for its resistance to heat and acids, found critical applications in spacecraft windows for NASA’s Gemini missions. “This discovery unlocks new possibilities for future high-performance materials,” Kubicki said. The successful demonstration provides a “transferable framework” that the researchers anticipate can be applied to other ZIF and metal-organic framework (MOF) glass types.

Looking ahead, the University of Birmingham reports that the next phase will focus on enhancing the materials’ stability and rigorously testing their performance in real-world technological settings. “This advance brings MOF glasses a step closer to real-world manufacturing,” Henke concluded. By bridging millennia-old artisanal knowledge with cutting-edge materials science, the discovery suggests that the past may hold the key to engineering the sustainable technologies of the future.