An international team of scientists has reached a major milestone in sustainable energy research, developing a highly efficient method for converting methane into ethanol.
Mechanism for photocatalytic conversion of methane to ethanol. Image Credit: Xie, J. et al., Nature (2025), https://doi.org/10.1038/s41586-025-08630-x
Their findings, published in Nature, highlight a photocatalytic approach that achieves an impressive 80 % selectivity and a methane conversion rate of 2.3 % in a single run using a packed-bed flow reactor. The system also boasts an apparent quantum efficiency (AQE) of 9.4 %, a strong indicator of its effectiveness in converting light into usable energy.
Background
Ethanol is widely recognized as a key component in the energy sector, serving as a liquid hydrogen carrier and a crucial feedstock for various industrial applications aimed at reducing carbon emissions. The global ethanol market exceeds $100 billion, with a steady annual growth rate of around 7 %. Meanwhile, methane—abundant in natural and shale gas—continues to be underutilized, often flared for heating despite its potential as a valuable chemical feedstock. However, its chemical stability presents significant challenges for efficient conversion.
Traditional methods rely on high-temperature, high-pressure syngas processes, which are both energy-intensive and inefficient in product selectivity. Direct methane-to-ethanol conversion has remained elusive due to difficulties in achieving selective carbon-carbon (C-C) coupling.
A New Approach to Catalytic Conversion
The breakthrough stems from the use of a covalent triazine framework (CTF-1) polymer, which features a unique intramolecular junction between alternating benzene and triazine units. This design enhances charge separation and prolongs charge lifetimes, while also enabling targeted adsorption of oxygen and water molecules.
This structure facilitates precise C-C coupling, minimizing the risk of overoxidation into carbon dioxide and water. When further enhanced with platinum, the catalyst demonstrates a highly promising ethanol production rate.
This is a step-change advancement in the photocatalytic conversion of methane into value-added green chemicals – not only in terms of a newly identified metal-free “intramolecular junction” for effective C-C coupling; but also by turning methane into a much more desirable liquid chemical, relatively efficiently at ambient conditions.
Zhengxiao Guo, Study Corresponding Author and Professor, Department of Chemistry, The University of Hong Kong
Comparison to Traditional Methods
Conventional methane conversion methods, such as Fischer-Tropsch synthesis, require extreme temperatures (> 700 °C) and pressures (~20 bar) to activate methane’s strong C-H bonds. These processes demand high energy input and multiple conversion steps.
Previous attempts at photocatalytic conversion have struggled with either low selectivity or efficiency due to limitations in catalyst design. The newly developed CTF-1 catalyst outperforms these methods, achieving over 20 times higher quantum efficiency while maintaining high selectivity.
Potential Applications and Broader Impacts
Methane, though a valuable resource, is also a potent greenhouse gas. Converting it directly into ethanol through a single-step photocatalytic process offers a promising route toward decarbonizing the chemical and fuel industries. Ethanol, being a liquid, is easier to store, transport, and distribute compared to gaseous hydrogen. It can be directly reformed onboard low-carbon vehicles, including those in urban transport, shipping, and emerging low-altitude aviation sectors. This advancement could play a crucial role in achieving carbon neutrality.
Future Research and Development
The research team, led by Professor Guo, plans to refine the catalyst design and further optimize the conversion process. These efforts will be part of a broader collaboration under the UGC Theme-Based Research Scheme and the RGC-EU Collaborative Innovation Scheme, aimed at accelerating sustainable chemical production.
With methane utilization remaining a key challenge in the transition to cleaner energy, this breakthrough offers a practical and scalable solution, opening new doors for the future of low-carbon fuel technologies.
Journal Reference:
Xie, J. et. al. (2025) Methane oxidation to ethanol by a molecular junction photocatalyst. Nature. doi.org/10.1038/s41586-025-08630-x