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

The storage of C2H2 and separating C2H2 from the mixture of CO2 or C2H4 are still huge challenges in industry due to their similar physical properties. Metal–organic frameworks (MOFs) as a new generation of high-capacity adsorbents can meet various separation needs. Here, honeycomb-like MOFs, named as [M3(OX)3(TPA)2] (SNNU-333, M = Co or Ni, OX = oxalic acid, TPA = Tri(pyridin-4-yl)amine) with tfz topology are successfully synthesized via the in situ ligand transformation process. SNNU-333 can be regarded as a pillar-layered framework with OX anions as pillars and [M3(TPA)2] as 2D layers or a rod-packing architecture with 1D inorganic [M(OX)(TPA)2] chains as rod-like building blocks. Such a linkage makes SNNU-333 highly porous networks with two types of micropores of about 6 and 12 Å, respectively. Unexpectedly, these MOFs with mononuclear building units are of good stability, and SNNU-333-Ni can keep the integrity of the framework in water and solution with pH values varying from 3 to 11 for 24 h. Taking advantage of the frameworks with dual porosity, SNNU-333 MOFs exhibit high C2H2 adsorption capacity as well as high separation performance of C2H2/CO2 and C2H2/C2H4 mixtures. The ideal adsorbed solution theory selectivity calculations, column breakthrough tests, and Grand Canonical Monte Carlo simulations further indicate SNNU-333 MOFs promising adsorbents for C2H2 adsorption and purification.