Role of Back-Donation Deciphering CO2 Adsorption Modes on 3d-Transition Metals.

The development of effective and sustainable catalysts for the long-term use of CO2 is highly dependent on understanding how CO2 is adsorbed and activated on catalysts, mainly based on transition metals. Since catalysis is inherently a localized phenomenon and CO2 tends to adsorb at the metal centers due to differences in electronegativity, detailed information on the mechanisms of CO2 capture can be obtained by studying simplified molecular models, such as transition-metal dimers. Using such dimer models, this article addresses the importance of d-orbitals that facilitate the adsorption and activation of a CO2 molecule. In addition, the influence of back-bonding is observed, where electrons from the filled 2π orbitals of CO2 are donated to the vacant orbitals of metal atoms, in different adsorption configurations of CO2 molecule. The findings elucidate a clear connection between back-bonding and CO2 adsorption mechanism, highlighting particular configurations that facilitate optimal activation. Through evaluation of the correlation among d-orbitals, back-bonding, and CO2 activation within transition-metal dimers, a viable approach is presented to design efficient catalysts to capture carbon dioxide.