In the relentless pursuit of cleaner and more sustainable energy sources, natural gas and biogas have emerged as pivotal fuels, mainly constituted of methane (CH₄). Nevertheless, these gases are seldom pure and contain impurities such as carbon dioxide (CO₂), which substantially diminish the energy value and induce corrosion in transportation pipelines. Addressing the challenge of efficiently separating CO₂ from methane-rich gas mixtures has gained significant attention, and recent breakthroughs in nanotechnology offer promising solutions.
Graphene, a two-dimensional allotrope of carbon known for its exceptional mechanical strength, chemical inertness, and thermal stability, has captivated scientists as a potential revolutionary material for gas separation membranes. Intrinsically impermeable to gases, pristine graphene’s utility lies in tailoring its atomic structure by introducing nanoscale pores. These engineered pores function as molecular sieves, enabling selective filtration based on size exclusion and chemical affinity.
A pioneering research team at Chiba University, Japan, spearheaded by Associate Professor Tomonori Ohba and researcher Shunsuke Hasumi, has unveiled cutting-edge developments in oxygen-functionalized graphene membranes that markedly enhance CO₂/CH₄ separation efficiency. The research, scheduled for publication in the February 2026 issue of the journal Carbon, reveals novel methodologies to fine-tune graphene’s properties, potentially transforming industrial gas purification processes.
The core concept revolves around optimizing pore size and surface chemistry of graphene membranes to exploit the distinct physicochemical properties of CO₂ and CH₄ gas molecules. If graphene pores are too large, both gases diffuse without discrimination, nullifying separation efficacy. Conversely, pores that approach a diameter of about 0.4 nanometers exhibit meaningful selectivity, as this dimension closely corresponds to the molecular dimensions of CO₂, thereby permitting its preferential passage.
To unravel the interplay between pore size and gas permeation, the researchers deployed an integrated approach combining experimental measurements with advanced molecular dynamics simulations. Using a custom mass spectrometry setup, gas fluxes of CO₂ and CH₄ across membranes were quantified. Concurrently, atomistic simulations modeled molecular trajectories and interactions within pores ranging from 0.21 to 0.99 nanometers. These simulations included considerations for both short-range steric effects and long-range Coulomb forces, delivering a comprehensive understanding of transport phenomena at the nanoscale.
Results illuminated an intriguing phenomenon: although porous graphene membranes inherently possess extremely high gas permeabilities, their selectivity deteriorates for pore diameters exceeding roughly 0.5 nanometers. Experimental evidence corroborated simulation predictions, albeit with noticeable deviations in CO₂ permeability attributed to the multi-layered nature of fabricated membranes, contrasting the idealized single-layer models in simulations.
A pivotal discovery addressed the biochemical environment of real-world graphene membranes, which naturally exhibit oxygen functional groups at inherent defects and pore edges. These oxygen atoms profoundly influence gas transport characteristics by preferentially interacting with CO₂ molecules. When the research team incorporated oxygen functionalization into their models, the membranes demonstrated substantially improved CO₂ permeability and selectivity over methane.
To validate these insights, graphene membranes underwent oxygen plasma treatment to deliberately augment oxygen-containing functional groups. Post-treatment membranes displayed remarkable improvements in separation performance, effectively aligning experimental outcomes with computational predictions. This synergy between oxygen chemistry and nanostructured pore design redefines graphene’s capabilities as a high-performance gas separation membrane.
The underlying mechanism emerges from the enhanced affinity between CO₂ molecules and oxygen functional groups localized at pore edges. The quadrupolar nature of CO₂ enables stronger electrostatic interactions with oxygen moieties, facilitating its preferential adsorption and transport. Methane, lacking comparable polarizability, experiences diminished interaction, resulting in enhanced molecular sieving.
This research heralds a new era for industrial gas purification. Oxygen-functionalized graphene membranes hold the potential to revolutionize biogas and natural gas processing by enabling rapid, energy-efficient, and selective separation of CO₂. The implications include reducing greenhouse gas emissions through lower energy consumption and enabling more economical production of high-purity methane fuels, ultimately contributing to cleaner energy infrastructures.
While intellectual promise is vast, challenges remain in scaling membrane fabrication to industrial volumes and ensuring membrane longevity under operational stresses. Nevertheless, Associate Professor Ohba emphasizes membrane separation’s trajectory as an environmentally friendly and scalable technology with transformative prospects for the global energy sector.
By harnessing molecular-level control over porosity and chemistry, the work exemplifies the integration of theoretical and experimental approaches to solve complex material challenges. The study’s compelling combination of fundamental physical chemistry and practical engineering paves the way for next-generation membrane materials that transcend current separation limits.
In the context of continually tightening environmental regulations and rising demand for sustainable energy, such graphene-based membranes could become indispensable tools for achieving high-efficiency carbon capture and utilization. Furthermore, the principles underlying oxygen functionalization may extend to other two-dimensional materials and separations tasks, broadening this research’s applicability.
Profoundly, this research not only advances gas separation science but also elevates graphene’s status from a model nanomaterial to a functional asset in industrial chemistry and environmental management. The work of Ohba and Hasumi represents a landmark in the quest to engineer tailored nanospaces that manipulate molecular behavior with unprecedented precision, ultimately steering humanity toward a cleaner energy future.
Subject of Research:
Nanotechnology, Materials Science, Chemical Engineering, Carbon Capture, Energy, Environmental Engineering
Article Title:
Enhancing the CO₂/CH₄ Gas Separation Performance of Graphene Membranes via Oxygen Functionalization
News Publication Date:
February 5, 2026
Web References:
https://www.sciencedirect.com/science/article/pii/S0008622325011637?via%3Dihub
References:
Hasumi, S., & Ohba, T. (2026). Enhancing the CO₂/CH₄ gas separation performance of graphene membranes via oxygen functionalization. Carbon, 248. https://doi.org/10.1016/j.carbon.2025.121147
Image Credits:
Associate Professor Tomonori Ohba, Chiba University, Japan
Keywords
Nanotechnology, Materials Science, Graphene, Gases, Chemical Engineering, Energy, Technology, Environmental Engineering, Carbon Capture
