Catalytic reduction of carbon dioxide to methanol over defect-laden hexagonal boron nitride: insights into reaction mechanisms

We present a density functional theory-based mechanistic understanding of CO2 hydrogenation to value-added products on a nitrogen-vacancy (VN) defect in hexagonal boron nitride (dh-BN). Activation occurs through back-donation to the π* orbitals of CO2 from the frontier orbitals (defect state) of the h-BN sheet that are localized near a nitrogen-vacancy. Subsequent hydrogenation to methanol (CH3OH) and formic acid (HCOOH) proceed through vacancy-facilitated co-adsorption of hydrogen and CO2. More importantly, our reaction pathway analyses complimented by microkinetic modeling indicate that dh-BN is potentially a low-temperature, selective catalyst for CO2 reduction to methanol. Our findings are in agreement with experiments conducted in a mechanical reactor that show high selectivity towards methanol formation for CO2 hydrogenation on defect induced h-BN.