Sandia National Laboratories researchers are pioneering a new approach to capture methane from biogas by using porous liquids — innovative materials that combine the characteristics of liquids with built-in empty spaces to selectively trap gas molecules. Scientists led by materials engineer Jessica Rimsza aim to harness methane, a potent and valuable energy source found in waste byproducts such as food scraps, manure and sewage, and separate it from other gases so it can be used more efficiently.
Biogas, a mixture of methane and other gases produced in places like wastewater treatment plants and agricultural operations, often goes underutilized because of challenges in separating methane from carbon dioxide and impurities. The team’s research focuses on tailoring porous liquids — combinations of liquid solvents and porous solid materials — so they can act like tiny caverns in a fluid state that absorb and store methane and other targeted gases.
These porous liquids are made by dispersing porous solids (such as zeolites, metal-organic frameworks, covalent organic frameworks or porous organic cages) within a solvent. Unlike typical liquids that absorb only a small amount of gas, the added solid structures provide free space that dramatically increases gas uptake. Rimsza notes that with hundreds of thousands of porous materials and tens of thousands of solvents available, the potential permutations could yield thousands of tailored porous liquids for specific applications.
The key challenge the team is addressing is selective methane capture: allowing methane molecules to migrate into the solvent and further into pore spaces, while excluding other gases like carbon dioxide. Once methane is captured, it can be released on demand and used in electricity generation, heating, industrial processes such as steel and glass production, or as feedstock for chemical products like hydrogen, methanol, ammonia and acetylene.
Importantly, research to date shows that in certain configurations, porous liquids can hold significantly more gas than expected from the individual components alone — in some cases capturing up to 40 times more gas than the solvent alone would permit. The liquid form also offers an integration advantage, as liquids can be handled within existing piping systems more easily than solid adsorbents that require specialized handling.
Porous liquids were first theorized in 2007 and proven in 2015, and Sandia’s work has expanded their applications toward energy and gas separation technologies. The team has filed broad patents on design principles for porous liquids and published scientific articles on various aspects of the research.
