Isotope effect of proton and deuteron adsorption site on zeolite-templated carbon using path integral molecular dynamics

To analyze the proton/deuteron (H/D) isotope effect on the stable adsorption sites on zeolite-templated carbon (ZTC), we have performed path integral molecular dynamics simulations including thermal and nuclear quantum effects with the semi-empirical PM3 potential at 300 K. Here, for the adsorption sites of additional proton (H^*) and deuteron (D^*), we chose different five carbon atoms labeled as α-, β₁-, β₂-, γ-, and δ-carbons from edge to bottom for inside of buckybowl (C₃₆H₁₂ and C₃₆D₁₂). The stable adsorption sites of D^* are observed on all carbon atoms, while those of H^* are not observed on δ-carbon atom, but only on α-, β₁-, β₂-, and γ-carbon atoms. This result is explained by the fact that H^* can easily go over the barrier height for hydrogen transferring from δ- to β₂-carbons at 300 K, since the zero-point energy of H^* is greater than that of D^*.