One‐dimensional metal–organic frameworks built by coordinating 2,4,6‐tris(4‐pyridyl)‐1,3,5‐triazine linker with copper nodes: CO₂ adsorption properties

Abstract

The reaction between 2,4,6-tris(4-pyridyl)-1,3,5-triazine (4-tpt) and copper(II) hexafluoroacetylacetone (Cu(hfa) 2 ) yields two different 1D metal-organic frameworks (MOFs), [(Cu(hfa) 2 ) 2 (4-tpt)] n (1) and [Cu(hfa) 2 (4-tpt)] n (2). The Cu:4-tpt ratio in the new MOFs is determined by the reaction medium, particularly, the solvent used. The two compounds have been fully characterized, including crystal structure elucidation. [(Cu(hfa) 2 ) 2 (4-tpt)] n (1), with a 2:1 Cu:4-tpt ratio, could be precipitated in either 1,1,2-trichloroethane or supercritical CO 2 . In (1), 4-tpt shows a tritopic coordination mode, but only half of the Cu(hfa) 2 subunits act as a node, thus connecting two 4-tpt and giving a 1D network. The other half of Cu(hfa) 2 subunits are connected only to one pyridine and thus protrude along the chains. The later Cu(hfa) 2 fragments show a labile character and can be dissolved in diethyl ether to give the second MOF [Cu(hfa) 2 (4-tpt)] n (2), with a 1:1 Cu:4-tpt ratio. The compound (2) has also a 1D structure, with all the incorporated copper atoms acting as nodes. In this case, the packing of the chains defines accessible channels, which are perpendicular to the chain axis. After activation, N 2 adsorption/desorption measurements at 77 K confirm the microporous character of (2) with an apparent surface area of 190 m 2 g À1 . Besides, at 273 K this material clearly shows a significant adsorption of CO 2 prompted by noncoordinated nitrogen in the triazine linker.