Nanostructured encapsulation for controlled CO2 storage as clathrate hydrate in sub-seabed saline sediments: Containment, stability, and field scale application toward decarbonization. A review

Abstract

Carbon dioxide (CO₂) sequestration via clathrate hydrate formation in sub-seabed saline sediments offers a promising solution for reducing anthropogenic CO₂ emissions. Nanostructured encapsulation using nanomaterials, such as carbon nanotubes, metal-organic frameworks (MOFs), graphene oxide, and bio-inspired designs has shown potential in stabilizing CO₂ within solid matrices, enabling controlled hydrate formation and storage. However, fluctuating pressure, temperature, and salinity conditions, especially in harsh environments, challenge encapsulation stability, requiring material optimization for sediment compatibility. Nanomaterials additives enhance hydrate stability, CO₂ absorption efficiency, and mass transfer, though the performance depends on type, size, texture, composition, and formation conditions. Synergistic effects between nanomaterials and surfactants/polymers further improve interfacial tension (IFT) reduction, induction time, and storage capacity. This work highlights key mechanisms governing nanomaterials' CO₂ uptake in subseafloor sediments, including adsorption/absorption, diffusion, structural modifications, confinement effects, and hydrophobic interactions. In addition, the study underscores advanced characterization techniques, such as Raman spectroscopy, XRD, and molecular dynamics, providing insights into structural and thermal properties, while field studies in regions like the North Sea and Norway highlight practical challenges. Despite progress, scalability, cost-effectiveness, and environmental safety under variable subsea conditions remain hurdles. Emerging innovations, such as stimuli-responsive nanomaterials and hierarchical encapsulation architectures, could optimize long-term CO₂ storage and controlled release. By integrating the collective findings drawn from both empirical data in published papers and theoretical deductions, this work provides a roadmap to enhance comprehension regarding the screening, design, formation, nucleation, and growth of CO₂ hydrate in nanostructured encapsulation system toward sustainable CO₂ storage and global decarbonization goals.