Carboxylate-assisted acylamide metal–organic frameworks: synthesis, structure, thermostability and luminescence studies

Abstract

We present a series of carboxylate-assisted ethylamide metal–organic frameworks, namely, Zn₂(L)₂(oba)₂·2H₂O(1, L = N1,N3-di(pyridin-3-yl)isophthalamide, H₂oba = 4,4′-oxybis(benzoic acid)), Zn₂(L)(nap)₂·(DMF)_2.5H₂O(2, H₂nap = 1,4-naphthalic acid, DMF = dimethylformamide), Cd(H₂O)(L) (ip)·3H₂O (3, H₂ip = 1,3-benzenedicarboxylic acid), Cd(L)(ip)·2H₂O(4). Polymer 1 crystallizes in the acentric Pca2₁ space group and presents an unprecedented topology prototype of noz-4-Pcca that allows three-fold interpenetration. Polymer 2 is a 3D supramolecular net with a considerable solvent-accessible void that is occupied by DMF and water molecules. As for polymers 3 and 4, the different formation of them is somewhat controlled by the concentration of initial materials such as 0.1 mmol Cd(NO₃)₂, L, ip in 8 mL water used for 3, 0.2 mmol Cd(NO₃)₂, L, ip in 8 mL water used for 4. In 3, a highly rare 1D porous ladder-type structure is observed, and further through hydrogen bonds a 2D supramolecular net is built. By contrast, a 3D α-Po net with two-fold interpenetration, based on a dinuclear Cd₂(CO₂)₄ building block, is observed in 4. Moreover, their thermostability and luminescence properties are explored.