Pillared-Layer Heterometallic Zn/Cd MOF for Natural Gas Upgrading and C3–C4 Hydrocarbon Recovery

Developing stable adsorbents for the separation of light hydrocarbons from natural gas is critical for methane purification and high-value C3/C4 hydrocarbon recovery. Herein we report a stable heterometallic Zn/Cd pillared-layer MOF (LIFM-268) featuring a doubly interpenetrated structure with unique hourglass-shaped Zn2Cd node. LIFM-268 exhibits outstanding thermal and chemical stability. Gas adsorption measurements reveal that its adsorption uptakes, isosteric heats of adsorption, and adsorption selectivities for C2–C4 hydrocarbons all far exceed those of CH4, following the order n-C4H10 > C3H8 > C2H6 > CH4. Crucially, dynamic breakthrough experiments using ternary and quinary simulated natural gas confirm that LIFM-268 can directly produce high-purity methane while efficiently capturing C3/C4 components. The material demonstrates excellent recyclability over five adsorption–regeneration cycles. Furthermore, theoretical simulations elucidate that the superior separation performance arises from abundant strong host–guest interactions, specifically C–H···O and C–H···π forces between long-chain alkanes and the framework built from aromatic ligands and trinuclear metal nodes. This work provides a promising adsorbent candidate for industrial natural gas upgrading and offers structural insights into the design of heterometallic MOFs for light hydrocarbon separation.