Assessment of density functional approximations for N2 and CO2 physisorption on benzene and graphene

Experimental isotherms of N-2 and CO2 on carbon-based porous materials and models of the physisorption of gases on surfaces are used to obtain the pore size distribution (PSD). An accurate modelization of the physisorption of N-2 and CO2 on the surface of carbon-based porous materials is important to obtain accurate N-2 and CO2 storage capacities and reliable PSDs. Physisorption depends on the dispersion interactions. High precision ab initio methods, such as CCSD(T), consider accurately the dispersion interactions, but they are computationally expensive. Double hybrid, hybrid and DFT-based methods are much less expensive. In the case of graphene, there are experimental data of the adsorption of N-2 and CO2 on graphite that can be used to build the Steele interaction potential of these gases on graphene. The goal is to find out hybrid and/or DFT methods that are as accurate as the CCSD(T) on benzene and as accurate as the experimental results on graphene. Calculations of the interaction energy curves of N-2 and CO2 on benzene and graphene have been carried out using the CCSD(T) method and several double hybrid, hybrid, and DFT methods that consider the dispersion interactions. The energy curves on benzene have been compared to the CCSD(T) and the energy curves on graphene have been compared with the Steele energy curves. The comparisons indicate that double hybrids with dispersion corrections and omega B97 based DFT methods are accurate enough for benzene. For graphene, only the PBE-XDM functional has a good agreement with the Steele energy curves.

Automated summary

This study investigates the physisorption of N-2 and CO2 on carbon-based porous materials and the pore size distribution. By comparing the interaction energy curves obtained from different calculation methods with experimental results, it is found that double hybrid methods with dispersion corrections and omega B97-based DFT methods are accurate for benzene, while only the PBE-XDM functional shows good agreement with the Steele energy curves for graphene.