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 C2H2 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 [M-3(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 [M-3(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 angstrom, 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/C2H2 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.