Scalable Co–Ni Mixed MOF Featuring Dual Functional Sites for C2H2 Separation with Excellent Shaping Performance

Abstract

The purification of C₂H₂ from gas streams containing CO₂ persists as a formidable challenge in petrochemical manufacturing, primarily attributed to the identical kinetic diameters and the limitations of conventional separation methods. Herein, we report a scalable Co–Ni mixed metal–organic framework (MOF), Co(bpy)[Ni(CN)₄], featuring dual functional sites, namely, unsaturated Ni²⁺ open metal sites (OMS) and Lewis basic nitrogen atoms, for efficient C₂H₂ capture. The framework exhibits a good C₂H₂ uptake of 51.5 cm³ g^–1 at 298 K and 1 bar, surpassing that of many popular MOFs. Synergistic interactions between C₂H₂ and the dual sites, as revealed by DFT calculations, enable excellent IAST selectivity for equimolar C₂H₂/CO₂ (5.9) and C₂H₂/CH₄ (26.3) mixtures. Dynamic breakthrough experiments confirm robust separation performance under humid conditions, across temperatures (278 to 313 K), and over multiple cycles without degradation. Furthermore, shaping the MOF into pellets using polyvinyl butyraldehyde (PVB) binder retains its porosity and enhances processability, achieving a dynamic C₂H₂ capture capacity of 37 cm³ g^–1 from C₂H₂/CH₄ breakthrough separation. This work demonstrates a scalable, stable, and shapeable MOF with dual functional sites, offering a practical solution for industrial gas separation.