Paired interacting orbitals (PIO) study of Mo/SiO2 and Mo/HZSM-5 catalysts for olefin metathesis

► Paired interacting orbitals method is applied for Mo/SiO2 and Mo/HZSM-5 catalysts. ► Ethene cycloaddition to the surface Mo methylidene species is studied. ► Electronic structure of ethene complexes depends on the support properties. ► The bonds in the transition states are formed in an asynchronous manner. ► Total overlap population is proposed as a reactivity index.