International audienceUsing first principle methodologies, we investigate the subtle competition between s H-bond and pstacking interaction between CO2 and imidazole either isolated, adsorbed on a gold cluster or adsorbedon a gold surface. These computations are performed using MP2 as well as dispersion corrected densityfunctional theory (DFT) techniques. Our results show that the CO2 interaction goes from p-type stackinginto s-type when CO2 interacts with isolated imidazole and Au clusters or surface. The balance betweenboth types of interactions is found when an imidazole is attached to a Au20 gold cluster. Thus, thepresent study has great significance in understanding and controlling the structures of weakly-boundmolecular systems and materials, where hydrogen bonding and van der Waals interactions arecompeting. The applications are in the fields of the control of CO2 capture and scattering, catalysis andbio- and nanotechnologies