Comparative study of metal–organic frameworks synthesized via imide condensation and coordination assembly

Abstract

A series of metal–organic frameworks (1-XDI) have been synthesized by imide condensation reactions between an amine-functionalized pentanuclear zinc cluster, Zn₄Cl₅(bt-NH₂)₆, (bt-NH₂ = 5-aminobenzotriazolate), and organic dianhydrides (pyromellitic dianhydride (PMDA), naphthalenetetracarboxylic dianhydride (NDA), 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (HFIPA)). The properties of the 1-XDI MOFs have been compared with analogues (2-XDI) prepared using traditional coordination assembly. The resulting materials have been characterized by ATR-IR spectroscopy, acid-digested ¹H NMR spectroscopy, elemental analysis, and gas adsorption measurements. N₂ adsorption isotherm data reveal modest porosities and BET surface areas (30–552 m² g⁻¹). All of the new 1-XDI and 2-XDI MOFs show selective adsorption of C₂H₂ over CO₂ while 2-PMDI and 2-BPDI exhibit high selectivity toward C₃H₆/C₃H₈ separation. This study establishes imide condensation of preformed metal–organic clusters with organic linkers as a viable route for MOF design.