Effect of Flexibility on Thermal Transport in Breathing Porous Crystals
Kutay B. Sezginel, Sangsuk Lee, Hasan Babaei, Christopher E. Wilmer
Abstract
With the aim of understanding heat transfer during structural changes in breathing porous crystals upon gas loading, we study the effect of pore expansion on the thermal conductivity of a series of idealized materials containing adsorbed gas using molecular dynamics simulations. We calculated the thermal conductivity in three main axes of the crystal lattice starting from a tilt angle of 40° to represent the closed form of the crystal up to a tilt angle of 90° to represent the open form. With no gas present, the thermal conductivity increases in the tilt direction with pore expansion whereas thermal conductivity in other directions remains unchanged. In the presence of adsorbed gas, porous crystals at all states of expansion experience reduced thermal conductivity due to phonon scattering introduced by gas–crystal interactions. Similarly, the thermal conductivity in the tilt direction increases as the pore expands; however, the increase is less pronounced compared to the case with no gas present in the pores. We also show that the diffusivity of gas increases during pore expansion, facilitating mass transport.