Interlayer Symmetry Control in Flexible-Robust Layered Metal–Organic Frameworks for Highly Efficient C₂H₂/CO₂ Separation

Abstract

Removal of the CO₂ impurities from C₂H₂/CO₂ mixtures is an essential process to produce high-purity C₂H₂. Fabricating an adsorbent capable of discriminating these species, which have close kinetic diameters, is critical for developing advanced adsorption processes. Herein, we demonstrate a strategy to exploit the tunability of interlayer and intralayer spaces of two-dimensional (2D) layered metal-organic frameworks to achieve high performance for C₂H₂/CO₂ separation. This indicates that interlayer symmetrical control can achieve more efficient packing of C₂H₂ into Ni(4-DPDS)₂CrO₄, with a high C₂H₂ capacity of 45.7 cm³·g^-1 at 0.01 bar and a selectivity of 67.7 (298 K, 1 bar), which strikes a good balance between working capacity and separation selectivity compared to other isostructural Ni(4-DPDS)₂MO₄ (M = Mo, W). Crystallographic studies and DFT-D calculations reveal that such a C₂H₂-selective adsorbent possesses strong binding interactions due to the tailored pore confinement provided by the angular anions and rich electronic environment. Experimental breakthrough results comprehensively demonstrate the efficient C₂H₂/CO₂ separation performance of this unique material.