Unveiling the hidden mechanism on adsorption–deformation coupling: A perturbative insight

Adsorption‐induced deformation (AID) in porous media is a two‐way coupled phenomenon, involving not only the triggering of deformation by adsorption but also the feedback modulation of adsorption by deformation. The inherent complexity makes it challenging to accurately describe AID. Generally, adsorption and deformation should be determined within a unified theory. Here we develop an innovative method for AID. Regarding the deformation as a perturbation to the initial pore, we expand the grand potential of fluid in the deformed pore around that in the initial pore. So, the deformation relates solely to the mechanical information in the initial pore, and the coupling effect is incorporated into the h.o.t. of the expansion. By applying this framework to confined methane, it is found that in pores under 1 nm, the coupling effect is significant, while in even larger pores, the zeroth approximation still works fine.