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

Reactions of Zn(NO3)(2)center dot 6H(2)O with 1,2,4-triazole (Htrz) and 1,3,5-benzenetricarboxylic acid (H3BTC) or 5-sulfoisophthalic acid (5-H3SIP) afforded two coordination polymers, {[Zn-5(mu(3)-OH)(2)(trz)(2)(BTC)(2)(DMF)(2)]center dot x(solvent)}(n) (1) and {[Zn-7(trz)(8)(5- SIP)(2)(H2O)(4)]center dot 4(H2O)}(n) (2). Compound 1 has pentanuclear [Zn-5(mu(3)-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/N-2 adsorption selectivities due to its carboxylate oxygen decorated pore environment. Compound 2 contains a rare 3D zinc-triazolate framework constructed from a pentanuclear [Zn-5(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 zinctriazolate framework through Zn-O bonds, leading to a non-porous 3D structure of 2. Introduction of BTC3- into the zinctriazolate 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.