The molecular design of coordination polymers (CPs) and metal-organic frameworks (MOFs) has attracted increasing attention in the areas of inorganic chemistry and functional materials. In this study, a new series of 2D CPs and 3D MOFs was hydrothermally assembled from metal(II) chlorides and 2,2'-((4-carboxy-1,2-phenylene)bis(oxy))diacetic acid (H3cpbda) as a flexible and little-explored tricarboxylate linker. Additionally, several types of aromatic N,N-donor auxiliary ligands were used to promote crystallization, namely, 1,10-phenanthroline (phen), 4,4'-bipyridine (bipy), bis(4-pyridyl)amine (bpa), 1,2-di(4-pyridly)ethylene (dpey), or 1,2-di(4-pyridly)ethane (dpea). The obtained products were fully characterized and identified as M3(μ6-cpbda)2(phen)2n·4nH2O (M = Zn (1), Cd (2)), Co3(μ5-cpbda)2(μ-bipy)2n·2nH2O (3), Zn3(μ5-cpbda)2(μ-bipy)2n (4), Zn(μ3-cpbda)(Hbpa)n·4nH2O (5), Zn4(μ3-cpbda)2(μ-OH)2(μ-dpey)3(H2O)2n·2nH2O (6), Co3(μ4-cpbda)2(μ-dpey)3n·2nH2O (7), and Ni3(μ4-cpbda)2(μ-dpea)3n·2nH2O (8). Their structural and topological features were also explored, allowing us to identify a diversity of 2D and 3D coordination networks. Remarkably, Zn-based coordination polymers 5 and 6 revealed a high catalytic activity and reusability in the condensation reaction between benzaldehyde and malononitrile (or ethyl cyanoacetate), leading to almost quantitative product yields (99%) under optimized conditions. The present work contributes to widening the family of CPs/MOFs assembled from flexible polycarboxylate linkers and highlights a promising application of these compounds in heterogeneous catalysis.
Dou et al. (Sat,) studied this question.