An alternative approach is the validation of FF parameters against electronic structure calculations, which can also be employed for cases where no experimental adsorption data are (yet) available. Moreover, an analysis of the results obtained at a higher level of theory can provide insights into the nature of the host-guest interactions. Given its good scaling behaviour and efficient implementation for periodic systems, density functional theory (DFT) is the most widely applicable electronic structure method for these systems. Due to the well-known shortcomings of standard DFT in describing long-range dispersion interactions, which play an important role for adsorption phenomena, recent investigations have usually employed dispersion-corrected "flavours" of DFT. For example, the DREIDING calculations carried out in one of the aforementioned studies were supplemented by DFT calculations for selected systems which used the Perdew-Burke-Ernzerhof (PBE) functional with a D3 dispersion correction. It was shown that FF and DFT give, by and large, the same trends, validating the conclusions drawn from the DREIDING calculations. On the basis of preliminary results obtained in the context of the present study, the rev-vdW-DF2 functional, which includes a nonlocal dispersion correction, was used in recent DFT studies of carbamazepine and triclosan adsorption in all-silica and high-silica zeolites. Schwalbe-Koda and Goméz-Bombarelli compared binding energies obtained from static and dynamic DREIDING calculations to reference values from DFT optimisations and DFT-based MD simulations using the PBE-D3 functional, considering a total of 227 combinations of zeolites and organic structure-directing agents (OSDAs). Pointing out that the PBE-D3 functional tends to overbind guest molecules (see below), they noted that it provides a good balance between accuracy and computational cost compared to more sophisticated approaches. Altogether, they observed a good correlation between FF and DFT calculations, especially when using the "frozen-pose" method to compute the DREIDING binding energies (calculation of the host-guest binding energy without relaxation of zeolite and OSDA). They proposed this method for large-scale FF-based screening studies of zeolite-OSDA pairs. It is well established that DFT interaction energies show a strong dependence on the choice of exchange-correlation (XC) functional, which governs the description of short-range interactions, and (if used) the method to include long-range dispersion interactions. As a large variety of XC functionals and dispersion correction schemes are available, there is a plethora of possible combinations. Several authors have compared different approaches by calculating adsorption energies of small molecules (hydrocarbons, alcohols, CO2, H2O) in all-silica zeolites, as well as protonated and cation-exchanged zeolites, using values extrapolated from experiment and/or results of higher-level calculations as benchmarks.