Spatial-Interactive Synergistic Confinement in Isoreticular Metal–Organic Frameworks for Facilitating C2H2 Separation from CO2 with Record Packing Density

The synchronous implementation of precise molecule recognition and efficient gas accumulation in porous materials is highly desirable but challenging for physisorptive separation/storage applications. Here, we demonstrate the feasibility of achieving effective acetylene (C₂H₂) purification from a C₂H₂/CO₂ mixture with record-high gas packing density by modulating the pore size and interpenetrating symmetry in three isomorphic pillar-layered MOFs (CTGU-41/42/43). The 1D rectangular narrow channels and regularly arranged paired binding sites trigger spatial-interactive synergistic confinement (SISC), enabling suitable molecular orientation and spacing distances during C₂H₂ adsorption within these MOFs. In particular, CTGU-41 exhibits exceptional adsorption selectivity (41.4) toward the C₂H₂/CO₂ mixture (v/v, 50/50) with a record-high C₂H₂ storage density of 0.91 g mL^-1 at 298 K and 100 kPa, which, to the best of our knowledge, surpasses the density of solid-C₂H₂ (4.2 K) for the first time. The practical C₂H₂/CO₂ separation ability of CTGU-41/42/43 is further validated by column breakthrough experiments with high purity of C₂H₂ (>99.0%) and good separation factors (6.7-11.3). The SISC mechanism clarified in this work deepens the fundamental understanding of dense gas arrangement in specific adsorption space, which can be generalized to other challenging gas separation and storage applications.