Catalytic Coupling of CH4 with CO2 and CO by a Modified Human Carbonic Anhydrase Combined with Oriented
External Electric Fields: Mechanistic Insights from DFT Calculations
posted on 2020-12-09, 16:38authored byDenghui Ma, Hujun Xie, Zexing Cao
The leading edge of biocatalysis
is human intervention to expand
the specificity of the reactions, so that enzymes can catalyze an
impressive range of challenging chemical reactions. Here density functional
theory (DFT) calculations were used to explore the catalytic coupling
of CH4 with CO2 and CO into value-added chemicals
by a rhodium(I)-substituted human carbonic anhydrase [Rh(hCAII)] under
the oriented external electric fields (OEEFs), and possible mechanisms
and OEEF effects have been discussed. The DFT calculations show that
the rate-determining step for the catalytic coupling of CH4 and CO2 into acetic acid is CO2 insertion
and the formation of a C–C bond, and the application of OEEF
(Fx = +0.0075 au) can
remarkably reduce the free energy span from 37.4 to 19.3 kcal/mol.
The coupling of CH4 with CO into acetaldehyde has a barrier
requirement of below 28.0 kcal/mol. On the basis of the present results,
the artificial carbonic anhydrase is very promising for the conversion
of carbon-based small molecules with the judicious use of OEEFs.