A Rigid, Stable, and Scalable Aliphatic MOF Adsorbent for Efficient C₂H₂/CO₂ Separation with Record Acetylene Packing Density

Integrating separation parameters such as high adsorption capacity and selectivity, moderate adsorption enthalpy (Q_st), along with industrial factors including cyclic stability, cost-effectiveness, and scalability into a single adsorbent remains highly challenging due to inherent trade-offs among these properties. Herein, we strategically leverage the coordination modes of aliphatic ligands to significantly enhance C₂H₂/CO₂ separation performance. The structure flexibility and pore metrics are finely modulated by hydroxylated aliphatic acid (DLmal). As a result, the rigid Zn-bpy-DLmal exhibits an exceptional C₂H₂ adsorption capacity of 1.4 mmol g^-1 at 0.01 bar, high C₂H₂/CO₂ selectivity (49), and moderate C₂H₂ Q_st value (38.4 kJ mol^-1). Notably, it achieves record-high C₂H₂ packing densities of 347 g L^-1 at 0.01 bar and 747 g L^-1 at 0.5 bar. Furthermore, the scale-up production of Zn-bpy-DLmal to kilogram quantities has been successfully achieved at an estimated cost of $74 per kilogram. Dynamic breakthrough experiments confirm its practical C₂H₂/CO₂ separation performance with excellent cyclability under high flow rates and both dry and humid conditions. Moreover, two-bed pressure swing adsorption simulations demonstrate a high-purity C₂H₂ (>99%) yield of 14.64 mol with a recovery of 88.2% per cycle.