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Clay-based marine sediments have great potential for safe and effective carbon dioxide (CO 2 ) encapsulation by storing enormous amounts of CO 2 in solid gas hydrate form. However, the aging of clay with time changes the surface properties of clay and complicates the CO 2 hydrate formation behaviors in sediments. Due to the long clay aging period, it is difficult to identify the role of clay aging in the formation of CO 2 hydrate in marine sediments. Here, we used ultrasonication and plasma treatment to simulate the breakage and oxidation of clay nanoflakes in aging and investigated the influence of clay aging on CO 2 hydrate formation kinetics. We found that the breakage and oxidation of clay nanoflakes would disrupt the siloxane rings and graft hydroxyl on the clay nanoflakes. This decreased the negative charge density of clay nanoflakes and weakened the interfacial interaction of clay nanoflakes with the surrounding water. Therefore, the small clay nanoflakes enriched in hydroxyl would disrupt the surrounding tetrahedral water structure analogous to the CO 2 hydrate, resulting in the prolongation of CO 2 hydrate nucleation. These results revealed the influence of the structure-function relationship of clay nanoflakes with CO 2 hydrate formation and are favorable for the development of hydrate-based CO 2 storage., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)