Site-Specific Carbonylation of Dimethoxymethane over Brønsted Acids in the Opened Sodalite Cages of FAU Zeolite

Methyl methoxyacetate (MMAc) is a valuable platform molecule used in biodegradable polymers, polyester fibers, and fine chemicals. While zeolite-catalyzed carbonylation of dimethoxymethane (DMM) to MMAc is a sustainable route, achieving high selectivity, stability, and efficiency simultaneously remains challenging. Herein we demonstrate that strategically opening sodalite (SOD) cages within FAU-type zeolites creates optimal Brønsted acid microenvironments for DMM carbonylation. An H-FAU-I-F zeolite (Si/Al ≈ 6), prepared via mild NH4F treatment to open SOD cages, maintained 90% MMAc selectivity and a space-time yield of 0.7 g·g–1·h–1 over 500 h of continuous operation─representing unprecedented catalytic activity and stability. Solid-state NMR studies (using 2H-DMM and 13CO) revealed preferential enrichment of DMM and CO within the opened SOD cages. In situ 1H–13C CP MAS NMR directly captured the insertion of CO into DMM occurring specifically in SOD nanoreactors. DFT calculations attributed their superior activity to enhanced acid strength and transition-state stabilization. This work establishes a cage-engineering strategy for designing efficient and durable industrial carbonylation catalysts.