• CO2 capture;
  • high-level ab initio;
  • binding energy;
  • aromatic ring;
  • π–π interaction

The π–π interactions between CO2 and three aromatic molecules, namely benzene (C6H6), pyridine (C5H5N), and pyrrole (C4H5N), which represent common functional groups in metal-organic/zeoliticimidazolate framework materials, were characterized using high-level ab initio methods. The coupled-cluster with single and double excitations and perturbative treatment of triple excitations (CCSD(T)) method with a complete basis set (CBS) was used to calibrate Hartree–Fock, density functional theory, and second-order M⊘ller–Plesset (MP2) with resolution of the identity approximation calculations. Results at the MP2/def2-QZVPP level showed the smallest deviations (only about 1 kJ/mol) compared with those at the CCSD(T)/CBS level of theory. The strength of π–π binding energies (BEs) followed the order C4H5N > C6H6 ∼ C5H5N and was roughly correlated with the aromaticity and the charge transfer between CO2 and aromatic molecule in clusters. Compared with hydrogen-bond or electron donor–acceptor interactions observed during BE calculations at the MP2/def2-QZVPP level of theory, π–π interactions significantly contribute to the total interactions between CO2 and aromatic molecules. © 2013 Wiley Periodicals, Inc.