Carbon dioxide capture by nitrogen containing organic materials - A density functional theory investigation

Abstract

The present work deals with study and analysis of density functional theory (DFT) methods for carbon dioxide capture using nitrogen containing organic polymerix materials. Nitrogen containing organic materials as potential candidates for CO2 capture is examined by using various density functional methods. The performance of a set range of several density functionals from the representative families of pure generalized gradient approximation (GGA), meta-GGA, hybrid, long range corrected (LRC) and dispersion corrected functionals were considered for their assessment in calculating binding energies associated with gas molecules (CO2 and N-2) with the nitrogen containing model systems. The theory behind the different classes of density functionals was discussed and the functionals were assessed using statistical parameters such as mean average binding energy values, mean absolute errors and root mean square deviations in calculating the binding energies with the gas molecules. A total of 80 method/basis set combinations were examined through the analysis of binding energies of the gas molecules (CO2 and N-2) with various nitrogen containing aromatic frameworks. Unlike previosly reported DFt benchmarks, which calculate single point energies, in this work we have calculated binding energies for the geometries optmizied at each theoretical methods. For comparision the complexes were euavluated using Moller-Plesset perturbation method of second order MP2/aug-cc-pVDZ level theory to yield a best estimate of binding energies. We found that conventional functionals are not suitable for N-conatining model systems and tend to overestimate or understimate the binding energies. Considering both accuracy and efficiency the functionals we recommend are omega B97X-D, CAM-B3LYP and M06-2X. Also the functionals omega B97, omega B97X, PBE0 and M06-HF show relatively less errors and give reliable binding energies for the complexes. We have also discussed the mechanism for carbon dioxide interaction with polymer fragment anf functional groups in the model cluster systems. The conclusions obtained in the study would help in increasing awareness of the strengths and weaknesses of the DFT methods and assist the experimental researchers in efficient molecular engineering of porous covalent architectures for carbon dioxide capture. (C) 2018 Elsevier B.V. All rights reserved.