Methane hydrate nucleation frustration and dimensional reduction of structural order under nanoconfinement

Methane hydrate nucleation under nanoconfinement remains poorly understood due to the complex interplay between geometric restriction and molecular ordering. Here, we investigate the structural organization of water-methane systems confined between silica planar slit pores with widths ranging from 1 to 5 nm and temperatures between 250 and 295 K. Three-dimensional radial distribution functions reveal a clear suppression of hydrate-like ordering at strong confinement (below 2 nm), indicating frustrated nucleation. In contrast, projected two-dimensional correlations exhibit pronounced in-plane structural organization, evidencing a confinement-induced reduction in the dimensionality of molecular order.