For the temperature range of interest for gas separation applications (i.e., 260-400K), Kapil et al. have shown that the contributions from gas molecules to the total heat capacity of the gas-framework system is a function of the gas molecule and proportional to the amount of adsorbed gas. This is due to the fact that the contribution of host-guest interactions to the heat capacity are negligible in this temperature range. As the contribution of gas molecules can be added to the heat capacity of the empty framework, in this study, we focus on predicting the heat capacity of an empty framework. To account for anharmonic and nuclear quantum effects, path integral molecular dynamics simulations can be used. Nuclear quantum effects are of particular importance at very low temperatures. We use the harmonic approximation, as previous studies have shown that it gives sufficient accuracy for the heat capacity of an empty framework for the temperature range of interest for gas separation applications. However, it is important to note that the harmonic approximation might fail to correctly describe flexible materials, and it will be interesting to investigate the extent of validity of this approximation for estimating the heat capacity of these materials in the future. The details of computational procedure to compute harmonic frequencies are explained in method section and SI.