Dual pore-size sieving in a novel oxygenate-pillared microporous adsorbent for C6 alkane isomers separation

Adsorbents executing molecular sieving mechanisms for the efficient separation of n-hexane (C6) alkane isomers require delicate pore size control, but afford unsatisfactory single-component separations according to their branch degrees. Herein, we report a novel oxygenate-pillared microporous adsorbent, MoOFOUR-Co-tpb, ([Co(tpb)₂MoO₄], tpb = 1,2,4,5-tetra(pyridin-4-yl) benzene), with three gourd-shaped channels for dual pore-size sieving of C6 isomers. In particular, MoOFOUR-Co-tpb excludes 2,2-dimethylbutane, while 3-methylpentane (3MP) can enter one channel showing a high uptake of 82.6 mg g⁻¹, contrasting to the n-hexane (nHEX) adsorption by two channels (136 mg g⁻¹). This dual pore-size control strategy renders a record high equilibrium–kinetic combined selectivity for nHEX/3MP (30.2). Moreover, three- and five-component breakthrough experiments confirm the practical separation performances and cycling stability. Multiple theoretical simulations reveal the separation mechanism and adsorption sites.