Wave propagation in fluid-saturated nanoporous media: Upscaling molecular mechanics into continuum-level description.

Understanding how mechanical, thermodynamic, and acoustic properties emerge in fluid-saturated nanoporous materials remains a major challenge due to the breakdown of classical continuum assumptions at molecular length scales. Here, we present a multiscale framework that extends linear chemo-poroelasticity theory to describe the coupled response of nanoporous solids and confined fluids to mechanical wave excitation. The effective poromechanical parameters-elasticity and stress-chemistry coupling tensors, scalar chemistry modulus, and fluid mobility tensor-are computed from atomistic simulations of methane adsorption and transport in a prototypical zeolite. These simulation-informed parameters are then embedded in a continuum model of mechanical wave propagation. This integrated approach enables the prediction of the effective wave speeds and attenuation as a function of frequency, fluid loading, and nanopore-scale structure. The methodology provides a physically grounded path for linking molecular interactions to macroscopic acoustic and elastic response. In turn, this framework offers opportunities for designing nanoporous materials with tailored transport, mechanical, and acoustical properties-particularly in the emerging field of nanoscale acoustics.