Alkaline oxide clusters inside zeolites catalyze the selective synthesis of ethyl methyl carbonate

• Ethyl methyl carbonate (EMC) is prepared by transesterification reaction with a simple catalytic method using solid catalysts. • Commercially available zeolite NaX gives a significant catalytic activity (65% conversion, 91% selectivity to EMC) without any pre-activation treatment. • After incorporation of alkaline oxide clusters inside the zeolitic framework, different basic and acid zeolites become extremely active (99% yield) while still selective to EMC (up to ≈80%). • The zeolites are recoverable and reusable at least 10 times in batch, and are implemented in flow. • The alkaline oxide clusters inside the zeolitic framework, i.e. K 2 O, boosts the catalytic activity without changing the nature of the zeolite host (H-USY is still acid). Ethyl methyl carbonate (EMC), as the simplest asymmetric carbonate, is considered a unique green liquid organic compound for lithium batteries (electrolyte) and gasoline blending (octane enhancer additive), with properties between dimethyl and diethyl carbonate. In accordance, its chemical production is expected to boost during the coming years, despite green chemical syntheses for EMC are still to be developed. Here we show the selective synthesis of EMC from DMC and ethanol with one of the cheapest commercially available solids, i.e. zeolites, as a heterogeneous catalyst for the reaction, surpassing most of the current soluble catalysts employed for this reaction. While a pristine commercial zeolite such as NaX already shows a significant catalytic activity (65% conversion, 91% selectivity to EMC) without any pre-activation treatment, is recoverable and reusable, and can be implemented in batch and in flow, the incorporation of alkaline oxide clusters inside the zeolitic framework, i.e. K 2 O, boosts the catalytic activity not only for the NaX zeolite but also for the parent H-USY and NaY zeolites, otherwise barely catalytically active for the reaction, to give yields up to >99% and ≈80% selectivity to EMC. These results bring a sustainable and cheap catalytic system for the production of EMC.