Breaking the methanol/dimethyl carbonate azeotrope using a metal-organic framework with tetrahedral potassium-ion cluster gates.

With the growing demand for high-purity dimethyl carbonate (DMC) in the battery industry, the separation of methanol (MeOH) and DMC azeotrope to achieve battery-grade purity (>99.99%) has become a pivotal bottleneck in the production of DMC. Here we design and synthesize an ionic metal-organic framework with tetrahedral potassium-ion clusters as pore gates that enables this separation. Although the ion cluster completely blocks the pore aperture, it permits MeOH transport through selective coordination bond reconstitution and cooperative deformation of the ion cluster. Benefiting from the ultrahigh MeOH/DMC selectivity (>3,300), high-purity DMC (>99.9999%) could be produced in a single adsorption process from an equimolar/azeotropic mixture of MeOH and DMC. This work presents a guest-binding counterion cluster gating mechanism different from conventional sieving of individual ions in porous materials, opening avenues for next-generation molecular sieves.