The standardized carbonates only received the minimum MMFF for relaxation. In order to ensure we are comparing minimum transition barriers between molecules, we identified the lowest energy monomer for each state along the reaction coordinate. With RDKit, 100 conformers are generated for each carbonate and state, which are then undergo geometry optimization with DFTB. For the transition state (TS) conformers, the transferred hydrogen atom, bonded oxygen atoms, and tetrahedral carbon are constrained during the relaxation, to preserve each of the three specific transition states undergoing optimization. For our benchmarked materials, the 10 conformers which showed the most structural diversity-as measured by RDKit-and are within the lowest 5 kcal/mol energetically, were then optimized at the B3LYP level to find the lowest energy conformation.