Catalyst design for sustainable and directional ethyl methyl carbonate synthesis

Ethyl methyl carbonate is widely recognized as a key electrolyte solvent for lithium-ion batteries; nevertheless, its efficient synthesis through ethanol-dimethyl carbonate transesterification continues to face significant challenges, primarily arising from azeotropic separation and the inherent activity-selectivity trade-off of traditional basic catalysts. This Highlight surveys recent advances in catalyst design for transesterification, covering both homogeneous and heterogeneous systems. In these reported systems, certain drawbacks persist, namely insufficient interfacial enrichment and sluggish mass transfer, which can result in poor product yield and selectivity. We then summarize an emerging adsorption microenvironment strategy that integrates flexible adsorption with selective molecular adsorption. Swellable, flexible frameworks increase the local reactant concentration and improve access to active sites, while tailored ion pairing and hydrogen bonding motifs preferentially activate ethanol and promote ethyl methyl carbonate desorption, thereby suppressing consecutive reactions. Representative poly(ionic liquid) catalysts and shaped flexible catalysts have demonstrated that rational control over swelling behaviour, cation and anion cooperativity, and particle size can deliver higher ethyl methyl carbonate yield, selectivity, and durability under continuous flow and reactive distillation conditions. Finally, we outline key opportunities in quantitative adsorption design, scalable shaping strategies, and broader extension to organic carbonate synthesis.