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

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.