Divergent CO2 Fixation Modes by Aluminum-Base Bimetallic Systems: Mechanism Investigations

Abstract

The conversion and utilization of carbon dioxide (CO₂) is a challenging contemporary issue in the present day, and the first step is the CO₂ fixation. Recently, the main group metal compounds have been found that have the analogous reactivity to transition metals and are capable of activating inert small molecules. In this work, the reaction mechanisms of [Al-M] (M = Zn, Be, Mg, and Ca) heterobimetallic compounds with CO₂ are investigated by density functional theory calculations. The calculated results indicate that the bimetallic main group compounds [AlAe] (Ae = Be, Mg, Ca) show similar activities near to that of [AlZn] and they can activate CO₂ at low temperature due to the low energy barriers. For both [AlAe] and [AlZn], AlC bond mode is the thermodynamic control and AlO bond mode is kinetic control pathway. At experimental conditions, AlC bond mode is the main reaction pathway for [AlAe], whereas for [Al-Zn], AlO bond mode is preferred. The reactivity is depended on AlM bond strength, the weaker AlM bond, the more reactivity of [Al-M] is.