As a key step in ethanol synthesis from syngas, zeolite-catalyzed carbonylation of dimethyl ether (DME) to methyl acetate (MA) has attracted much attention. Loading metal, especially Cu, into zeolites improves the formation of MA dramatically. As Cu-O has been identified as an active species in previous work, the present work is focused on the mechanism of carbonylation of DME over Cu/H-MOR based on results from in situ IR spectroscopic study and density functional theory (DFT) calculation. The results from the experiments and DFT calculations support a synergetic mechanism involving both the Cu and Bronsted acid sites for DME carbonylation on Cu/H-MOR. In the synergetic mechanism, the Cu-O site and the neighboring Bronsted acid site accommodate the coexistence of CH3- and CH3OH from DME adsorption and dissociation. The coadsorption of CO with the Cu-CH3 species facilitates CO insertion to form the acetyl species. This Cu bound acetyl species, Cu-COCH3, reacts with the adsorbed CH3OH to form MA. (C) 2018 Elsevier Inc. All rights reserved.