Lactic acid is a key building block for biodegradable plastics, but producing it efficiently from renewable biomass remains challenging. Researchers have now developed a defect-engineered metal-organic framework catalyst that converts glucose into lactic acid with substantially improved efficiency, while also showing activity toward raw biomass feedstocks.
The study, published in Sustainable Carbon Materials, introduces a modified nickel-based metal-organic framework called MOF-74(Ni)-50SA. The researchers partially replaced the conventional organic linker in MOF-74(Ni) with commercially available salicylic acid. This seemingly simple change deliberately introduced structural defects into the material and created more catalytically active sites.
Under optimized conditions, the catalyst converted 99.5% of glucose and achieved a lactic acid yield of 51.7% at 170 °C within four hours. When a more dilute glucose solution was used, the lactic acid yield increased to 68.7%.
"Instead of treating structural defects as imperfections, we used them as a tool to control the catalytic environment inside the MOF," said Jianjian Wang, corresponding author of the study at Chongqing University. "By engineering the organic linkers, we were able to generate oxygen vacancies and more coordinatively unsaturated nickel sites, which helped glucose enter the reaction pathway toward lactic acid more efficiently."
Metal-organic frameworks, or MOFs, are porous crystalline materials assembled from metal ions and organic linkers. Their structures can be chemically adjusted, making them attractive platforms for catalysis. In this study, introducing salicylic acid increased the concentration of oxygen vacancies and coordinatively unsaturated nickel sites while largely preserving the underlying MOF-74 framework. X-ray photoelectron spectroscopy and electron paramagnetic resonance measurements supported the formation of these defect sites.
Kinetic experiments also provided evidence for how the defects improved performance. The apparent activation energy for glucose conversion decreased from 79.3 kJ mol⁻¹ for unmodified MOF-74(Ni) to 69.6 kJ mol⁻¹ for MOF-74(Ni)-50SA. Further experiments suggested that the modified catalyst mainly accelerated the early conversion of glucose into reactive intermediates such as fructose, dihydroxyacetone and pyruvaldehyde, rather than the final conversion of those intermediates into lactic acid.
The catalyst also showed encouraging durability. After five consecutive reaction cycles, glucose conversion remained above 97% and lactic acid yield remained above 40%, although some activity loss was associated with a decrease in oxygen vacancies.
Importantly, the system was not limited to purified glucose. When corn cobs were used directly as a biomass feedstock, the catalyst produced a 62.8% lactic acid yield at 170 °C after four hours. Pine needles were more resistant to conversion, but increasing the temperature and reaction time raised their lactic acid yield from 5.6% to 22.4%.
The findings show that linker engineering can be used to tune defect chemistry in MOF catalysts and improve the aqueous conversion of renewable carbohydrates into lactic acid, while also revealing where further improvements are needed in converting reaction intermediates and more resistant biomass feedstocks.
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Journal reference: Tang Y, Huang H, Peng J, Yu H, Wang Y, et al. 2026. Tuning the formation of structural defects in metal–organic framework catalysts via linker engineering to boost the production of biomass-derived lactic acid. Sustainable Carbon Materials 2: e031 doi: 10.48130/scm-0026-0027
https://www.maxapress.com/article/doi/10.48130/scm-0026-0027
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About Sustainable Carbon Materials :
Sustainable Carbon Materials (e-ISSN 3070-3557) is a multidisciplinary platform for communicating advances in fundamental and applied research on carbon-based materials. It is dedicated to serving as an innovative, efficient and professional platform for researchers in the field of carbon materials around the world to deliver findings from this rapidly expanding field of science. It is a peer-reviewed, open-access journal that publishes review, original research, invited review, rapid report, perspective, commentary and correspondence papers.
