<p>The ability of calixarenes to form complexes with a wide range of charged ions, pharmaceutical compounds, and neutral gaseous molecules is a well-established phenomenon in supramolecular chemistry. In the present work, we are performing theoretical calculations to understand the complexation of CO₂ molecule with biologically important supramolecule, i.e., <i>p</i>-sulfonatocalix[4]arene (SC4A). We have performed a comparative study to check the stability of guest small molecule in unsubstituted calix[4]arene (C4A) and simultaneously with various sulfonatocalix[4]arene (SC4A) inclusion complex. All the theoretical calculations were done using density-functional theory at PBE-D3(BJ)/def2-TZVP level of approximation. Calculations like equilibrium geometry optimization, vibrational spectroscopy, global reactivity descriptors, thermodynamic quantities, and adsorption energy led us to the result that HOMO–LUMO gap increases upon complexation of CO₂ with chosen receptor. As sulfonation increases adsorption energy of guest CO₂ molecule decreases, i.e., stability of complex increases with progressive sulfonation.</p> Graphical abstract <p></p>