Honeycomb-Like Pillar-Layered Metal–Organic\nFrameworks with Dual Porosity for Efficient C₂H₂/CO₂ and C₂H₂/C₂H₄ Separations

Abstract

The\nstorage of C₂H₂ and separating C₂H₂ from the mixture of CO₂ or C₂H₄ are still huge challenges in industry due to\ntheir similar physical properties. Metal–organic frameworks\n(MOFs) as a new generation of high-capacity adsorbents can meet various\nseparation needs. Here, honeycomb-like MOFs, named as [M₃(OX)₃(TPA)₂] (SNNU-333, M = Co or Ni, OX =\noxalic acid, TPA = Tri­(pyridin-4-yl)­amine) with <b>tfz</b> topology\nare successfully synthesized via the in situ ligand transformation\nprocess. SNNU-333 can be regarded as a pillar-layered framework with\nOX anions as pillars and [M₃(TPA)₂] as 2D layers\nor a rod-packing architecture with 1D inorganic [M­(OX)­(TPA)₂] chains as rod-like building blocks. Such a linkage makes SNNU-333\nhighly porous networks with two types of micropores of about 6 and\n12 Å, respectively. Unexpectedly, these MOFs with mononuclear\nbuilding units are of good stability, and SNNU-333-Ni can keep the\nintegrity of the framework in water and solution with pH values varying\nfrom 3 to 11 for 24 h. Taking advantage of the frameworks with dual\nporosity, SNNU-333 MOFs exhibit high C₂H₂ adsorption\ncapacity as well as high separation performance of C₂H₂/CO₂ and C₂H₂/C₂H₄ mixtures. The ideal adsorbed solution theory selectivity\ncalculations, column breakthrough tests, and Grand Canonical Monte\nCarlo simulations further indicate SNNU-333 MOFs promising adsorbents\nfor C₂H₂ adsorption and purification.