H2O-Built Proton Transfer Bridge Enhances Continuous Methane Oxidation to Methanol over Cu-BEA Zeolite

摘要

Direct oxidation of methane to methanol (DMTM) is a big challenge in C-1 chemistry. We present a continuous N2O-DMTM investigation by simultaneously introducing 10 vol % H2O into the reaction system over Cu-BEA zeolites. Combining a D2O isotopic tracer technique and ab initio molecular dynamics (AIMD) simulation, we for the first time demonstrate that the H2O molecules can participate in the reaction through a proton transfer route, wherein the H2O molecules can build a high-speed proton transfer bridge between the generated moieties of CH3- and OH- over the evolved mono(mu-oxo) dicopper ([Cu-O-Cu](2+)) active site, thereby pronouncedly boosting the CH3OH selectivity (3.1 -> 71.6 %), productivity (16.8 -> 242.9 mu mol g(cat)(-1) h(-1)) and long-term reaction stability (10 -> 70 h) relative to the scenario of absence of H2O. Unravelling the proton transfer of H2O over the dicopper [Cu-O-Cu](2+) site would substantially contribute to highly efficient catalyst designs for the continuous DMTM.