video: This animation showcases the core workflow of the innovative CO2 conversion technology. First, the self-supporting MOF-based mixed-matrix membrane selectively filters impurities (SO2, NO, O2, N2) from dilute CO2 sources. Next, the enriched high-purity CO2 is fed into the electrolyzer, where the Bi nanoparticle catalytic layer converts it to formic acid (HCOOH) under acidic conditions. It marks the first direct electrochemical conversion of air to pure HCOOH.
Credit: ©Science China Press
For years, turning carbon dioxide (CO2) into useful chemicals has relied on high-purity CO2, a costly and energy-intensive process that limits real-world impact. Now, a research team led by Professor Xiao-Ming Chen and Professor Pei-Qin Liao from Sun Yat-Sen University has changed the game with an innovative electrolyzer design, recently published in National Science Review.
The key innovation? A self-supporting molecular sieve membrane made from metal-organic frameworks (MOF), which is a porous materials known for their exceptional ability to capture gases. This membrane is integrated directly into the electrolyzer, doing two critical jobs at once: it filters out impurities like sulfur dioxide (SO2), nitrogen oxides (NO), and oxygen (O2) from dilute CO2 sources (flue gas et al.), while concentrating the CO2 to levels high enough for efficient conversion.
When tested with flue gas (typically 15% CO2), the membrane boosted CO2 concentration to 82.5%. The electrolyzer then converted this enriched CO2 to formic acid (HCOOH), a valuable liquid fuel and industrial chemical, with nearly 100% Faradaic efficiency (a measure of reaction effectiveness) and a current of 9000 mA. After just 4 hours, it produced 23 mL of anhydrous, electrolyte-free formic acid that meets commercial standards. This marks the first time such a pure product has been made directly from flue gas via electrochemical reduction.
Even more impressively, the device works with ambient air, which contains just 0.04% CO2. Using a specialized MOF membrane (based on KAUST-7), the team concentrated air’s CO2 to 2.05% and achieved a formic acid Faradaic efficiency of 98.2%, with a yield rate 5,000 times higher than catalysts without the membrane, offering promise for confined spaces like submarines or space stations, where CO2 control is critical.
Beyond performance, the design delivers economic benefits. A techno-economic analysis showed using flue gas instead of pure CO2 cuts production costs by 15%, as it eliminates the need for pre-purification steps. The electrolyzer also avoids side reactions with impurities, thanks to the membrane’s selective filtering, ensuring consistent, high-quality output.
This breakthrough bridges the gap between lab research and industrial application, offering a scalable, low-cost way to turn waste CO2 (from power plants, factories, or even the air) into a valuable resource. It not only helps reduce atmospheric CO2 levels but also supports sustainable chemical production, a key element for global carbon neutrality goals.
About Sun Yat-Sen University
Sun Yat-Sen University (SYSU) is a leading public research university in China, renowned for its strengths in chemistry, materials science, and environmental technology. The MOE Key Laboratory of Bioinorganic and Synthetic Chemistry at SYSU, where this research was conducted, focuses on developing innovative materials and technologies for energy and environmental sustainability, driving solutions to global challenges like climate change.
Journal
National Science Review