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.