There is increasing experimental and computational evidence that presence of sorbate molecules within zeolites and other nanoporous crystals can alter thermal conductivity of these materials. This phenomenon is expected to have a profound effect on applications which combine adsorption of sorbate molecules with temperature control, e.g. microscopic adsorption chillers. In addition, this effect can open a route towards control of thermal conductivity via host-sorbate interactions. In this talk we present results of our ongoing research aimed at understanding of effects of the sorbate “rattling” on crystal lattice vibrations. This goal is accomplished by a combination of molecular dynamics (MD) simulations and a theoretical analysis of a Langevin Equation (LE) for the sorbate and lattice dynamics. In order to develop a fundamental understanding of phonon-sorbate interactions, we consider a simple cubic crystal with a spherical molecule adsorbed in one of its unit cells. Our MD simulations demonstrate that even for this simple system the dependence of thermal conductivity on the strength of the sorbate-host interactions is rather complex. In order to elucidate the interactions of the sorbate with various phonon modes, we perform a series of simulations of scattering of phonon wavepackets by sorbates. Further understanding of the phonon-sorbate interactions is achieved by development and solution of a LE for the sorbate degrees of freedom and the key lattice vibration modes, i.e. modes that strongly interact with the sorbate. The LE accounts for these modes explicitly, whereas all other lattice vibration modes are modeled as an effective thermal bath. Since the coupling of the key modes with the thermal noise is weak, the dynamics of the system are investigated by the perturbation of the Hamiltonian dynamics of the key modes. This theoretical analysis is validated by comparison with the results of the MD simulations.