Metal Organic Frameworks exhibit new and fascinating adsorption properties and flexibility. The coupling between those two aspect plays an important role to explain their behavior under adsorption of a fluid. This thesis aims at providing methods that are adapted to the study of these physical systems. In a first part, I present a method based on the calculation of a generalized density of states in the osmotic ensemble. This method enables us to efficiently obtain all thermodynamical quantities, and most specifically adsorption isotherms, adsorption-induced structural deformations, as well as the hysteresis observed during an adsorption-desorption cycle. In the second part, a analytical thermodynamical model has been developed to understand the behavior of flexible nanoporous materials under adsorption. This approach enables us in particular to derive a large number of informations from experimental datas.
