Coordination Polymers from 2-Chloroterephthalate Linkers: Synthesis, Structural Diversity, and Catalytic CO₂ Fixation

Abstract

In contrast to the broad use of terephthalic acid as a building block for generating metal–organic architectures, functionalized terephthalate ligands remain significantly less investigated. In the present study, 2-chloroterephthalic acid (CltaH2) was used as an unexplored linker for assembling a new series of metal­(II) coordination polymers (CPs) formulated as {[Cu2(μ-Clta)­(μ4 -Clta)­(bipy)2]­·2H2O} n (1), {[Cu2(μ-Clta)­(μ4 -Clta)­(phen)2]­·2H2O} n (2), [Co3(μ4 -Clta)3­(phen)2] n (3), {[Zn4(μ3-Clta)2­(μ4-Clta)­(μ3-OH)2­(phen)2]­·2H2O} n (4), {[Cd­(μ3 -Clta)­(phen)]­·H2O} n (5), [Co2(μ-Clta)­(μ4 -Clta)­(μ-bpa)2] n (6), [Zn2(μ4 -Clta)­(μ4 -biim)] n (7), and [Cd­(μ-Clta)­(H2biim)2] n (8). These compounds were prepared hydrothermally from the respective metal­(II) chlorides, CltaH2, and different N-donor supporting ligands acting as mediators of crystallization (i.e., bipy, 2,2′-bipyridine; phen, 1,10-phenanthroline; bpa, bis­(4-pyridyl)­amine; H2biim, 2,2′-biimidazole). The structures of the coordination polymers 1–8 range from one-dimensional chains (5 and 8) and two-dimensional layers (1–3) to three-dimensional (3D) frameworks (4, 6, and 7); the latter also include 3D + 3D interpenetrated examples (4, 6). Apart from different dimensionalities, the compounds also feature distinct topologies, namely, 3,4L13 in 1 and 2, 3,4,6L12 in 3, pcu in 4, SP 1-periodic net (4,4)­(0,2) in 5, sqc65 in 6, 2C1 in 8, and a new kir1 topology in 7. Given the similarity of the reaction conditions, the obtained wide diversity of structures is primarily determined by the type of metal­(II) node and/or crystallization mediator. All the CPs were also screened as heterogeneous catalysts in a model CO2 fixation reaction, namely, in the coupling of epoxide (epichlorohydrin) with carbon dioxide, under atmospheric pressure, and in the absence of added solvent, to produce the corresponding cyclic carbonate. The catalytic reactions were optimized for CP 4, which revealed the best activity (up to 71% product yields), good stability, and recyclability for up to four reaction steps. Finally, CPs 3–8 are the first examples of cobalt, zinc, and cadmium coordination compounds assembled from 2-chloroterephthalic acid, thus widening its very limited application in the design of functional metal–organic architectures.

Coordination Polymers from Biphenyl-Dicarboxylate Linkers: Synthesis, Structural Diversity, Interpenetration, and Catalytic Properties

“…The five-coordinate Zn1 center assumes a distorted trigonal bipyramidal {ZnN 2 O 3 } geometry that is built from three carboxylate oxygen atoms from two μ 2 -H 2 L 2 2– linkers and two N phen atoms. The Zn–N [2.072(5)–2.078(5) Å] and Zn–O [1.939(3)–2.329(4) Å] bonding distances agree with related literature data. ,, The H 2 L 2 2– block functions as a μ 2 -linker with mono- and bidentate carboxylate groups (Scheme , mode V). The carboxylate moieties are responsible for interconnection of Zn­(II) atoms to produce 1D zigzag chains (Figure b) of a 2C1 topological type (Figure c).…”

Zn(ii) metal–organic architectures from ether-bridged tetracarboxylate linkers: assembly, structural variety and catalytic features

“…The resulting network can be defined as a dinodal 3,4-linked layer with a 3,4L13 topology and a (4•6 2 ) 2 (4 2 •6 2 •8 2 ) point symbol. 42 Besides, H-bonds in 3 reinforce its 2D network (Fig. S3, Table S2, ESI †).…”

“…Despite the absence of a clear linkage of catalyst structure with its activity, a better performance of 1, 2, and 4 can be associated with their one-dimensional structures and the presence of open metal sites (Lewis acid sites) or labile H 2 O ligands. 42,[54][55][56] In fact, these catalysts may display zinc(II) centers that are more accessible for catalytic action in comparison to 3 and 5 that are 2D and 3D coordination polymers, respectively. These factors may potentially explain an enhanced catalytic activity of CPs 1, 2, and 4 in the Knoevenagel condensation reaction that follows a common mechanism described for other coordination polymer catalysts.…”

“…In pursuit of our general research line on probing various commercially available but still rarely used polycarboxylic acids as linkers for designing functional coordination polymers, [40][41][42][43] in the current work we have chosen two etherbridged tetracarboxylic acids: 3-(2,5-dicarboxyphenoxy) phthalic (H 4 dpa) and 5-(2,5-dicarboxyphenoxy)isophthalic acids (Scheme 1). These organic compounds can potentially act as versatile semi-flexible linkers for the synthesis of zinc(II) coordination polymers.…”

Coordination Polymers as Heterogeneous Catalysts for Water Splitting and CO2 Fixation

“…Kirillov and co-workers have used the chloro-functionalized terephthalate as a linker along with pyridine-containing coligands to synthesize Cu(II)-, Co(II)-, and Cd(II)-based MOFs/CPs. 11 The networks obtained have diversity in the form of dimensionalities, ranging from onedimensional to three-dimensional. All of the eight resulting network materials are shown to act as heterogeneous catalysts toward cyclic addition of CO 2 to epoxides.…”