Two Coordination Polymers Constructed from Pentanuclear Zinc Clusters with Triazolate and Benzenecarboxylate Ligands: Selective Gas Adsorption

Abstract

Reactions of Zn(NO3)2·6H2O with 1,2,4-triazole (Htrz) and 1,3,5-benzenetricarboxylic acid (H3BTC) or 5-sulfoisophthalic acid (5-H3SIP) afforded two coordination polymers, {[Zn5(μ3-OH)2(trz)2(BTC)2(DMF)2]·x(solvent)}n (1) and {[Zn7(trz)8(5-SIP)2(H2O)4]·4(H2O)}n (2). Compound 1 has pentanuclear [Zn5(μ3-OH)2] clusters, which are linked by the triazolate ligands to give a 2D layer. The 2D layer is further bridged by BTC3− ligands to form a 3D framework. The 3D framework of 1 has 1D channels filled by solvent molecules. Desolvated 1 shows a moderate CO2 uptake and high CO2/CH4 and CO2/N2 adsorption selectivities due to its carboxylate oxygen decorated pore environment. Compound 2 contains a rare 3D zinc-triazolate framework constructed from a pentanuclear [Zn5(trz)8] cluster wherein the five zinc atoms are arranged linearly. The 3D zinc-triazolate substructure has 1D open channels filled by 5-SIP3− ligands, which interact with the zinc-triazolate framework through Zn–O bonds, leading to a non-porous 3D structure of 2. Introduction of BTC3− into the zinc-triazolate system gave the porous structure of 1. While a variation of BTC3−, 5-SIP3− was introduced into the zinc-triazolate system yielding a non-porous structure of 2, demonstrating that the secondary ligands play an important role in the formation of the final structures.