A porous Zn(ii)-coordination polymer based on a tetracarboxylic acid exhibiting selective CO2 adsorption and iodine uptake

A porous Zn(ii)-coordination polymer, namely {[Zn2(μ8-abtc)(betib)]·DMF}n (1), was solvothermally synthesized from 3,3',5,5'-azobenzenetetracarboxylate (abtc4-) and 1,4-bis(2-ethylimidazol-1-yl)butane (betib) ligands and {[Zn2(μ8-abtc)(betib)]·H2O}n (2) was obtained through the immersion of 1 in methanol. Compounds 1 and 2 were structurally characterized via numerous techniques. Both compounds displayed a 3D porous framework with a 3,6-connected sqc5381 net. Compound 2a obtained at 140 °C from 2 exhibited gas and iodine adsorption properties. Interestingly, the compound adsorbed selectively CO2 with the uptake capacity of 54.02 cm3 g-1 (13.26%) over N2 (5.43 cm3 g-1) and CH4 (14.53 cm3 g-1) at 273 K. The compound also adsorbed iodine with the weights of 19.99% and 30.26% in solution and vapor phases, respectively. The single crystal X-ray result and Raman spectra showed the presence of iodine units in the pores of the framework.

Two zinc metal-organic framework isomers based on pyrazine tetracarboxylic acid and dipyridinylbenzene for adsorption and separation of CO2 and light hydrocarbons

Two highly porous metal-organic framework isomers Zn₂(TCPP)(DPB) (1 and 2, H₄TCPP = 2,3,5,6-tetrakis(4-carboxyphenyl)pyrazine and DPB = 1,4-di(pyridin-4-yl)benzene) were successfully synthesized using different solvents and acid species to adjust the topologies of these two MOFs. Both of them were constructed by paddlewheel Zn₂(COO)₄, TCPP^4-, and DPB ligands. In compound 1, the Zn₂(COO)₄ paddlewheel units were fitted together by the TCPP^4- ligands to form two-dimensional layers, which were further connected by DPB ligands as pillars to construct a two-fold catenated 3D framework. In compound 2, the cross-linkage of Zn₂(COO)₄ paddlewheel units and TCPP^4- ligands resulted in a three-dimensional framework of Zn-TCPP, in which DPB ligands coordinated to two axial vertical dinuclear Zn₂(COO)₄. Both activated MOFs exhibited permanent porosity with high BET areas (1324 m² g^-1 for 1 and 1247 m² g^-1 for 2) and possessed narrow pore size distributions (0.93 nm for 1 and 1.02 nm for 2). Moreover, the adsorption behaviors of the two activated MOFs for CO₂ and light hydrocarbons (C1, C2, and C3) at low pressure were evaluated and favorable selectivity was proven for C₃H₈/C₃H₆ over CH₄. These two MOF materials reported in this study for selective CO₂ and light hydrocarbon capture have immense potential applications for environmental protection.

H-Bonded and metal(ii)-organic architectures assembled from an unexplored aromatic tricarboxylic acid: structural variety and functional properties

This study reports the application of an aromatic tricarboxylic acid, 2,5-di(4-carboxylphenyl)nicotinic acid (H3dcna) as a versatile and unexplored organic building block for assembling a new series of metal(ii) (M = Co, Ni, Zn, Fe, and Mn) complexes and coordination polymers, namely [M(Hdcna)(phen)2(H2O)]·H2O (M = Co (1), Ni (2)), [Zn(μ-Hdcna)(phen)]n (3), [Co(μ-Hdcna)(bipy)(H2O)2]n·nH2O (4), [Zn2(μ-Hdcna)2(bipy)2(H2O)4]·6H2O (5), [Zn(μ3-Hdcna)(H2biim)]n (6), [Ni2(Hdcna)2(μ-bpb)(bpb)2(H2O)4] (7), [Fe(μ4-Hdcna)(μ-H2O)]n·nH2O (8), and [Mn3(μ5-dcna)2(bipy)2(H2O)2]n·2nH2O (9). Such a diversity of products was hydrothermally prepared from the corresponding metal(ii) salts, H3dcna as a principal multifunctional ligand, and N-donor mediators of crystallization (1,10-phenanthroline, phen; 2,2'-bipyridine, bipy; 2,2'-biimidazole, H2biim; or 1,4-bis(pyrid-4-yl)benzene, bpb). The obtained products 1-9 were fully characterized by standard methods (elemental analysis, FTIR, TGA, PXRD) and the structures were established by single-crystal X-ray diffraction. These vary from the discrete monomers (1, 2) and dimers (5, 7) to the 1D (3, 4, 6) and 2D (8, 9) coordination polymers (CPs). Structural and topological characteristics of hydrogen-bonded or metal-organic architectures in 1-9 were highlighted, revealing that their structural multiplicity depends on the type of metal(ii) source and crystallization mediator. Thermal stability as well as luminescent, magnetic, or catalytic properties were explored for selected compounds. In particular, the zinc(ii) derivatives 3, 5, and 6 were applied as efficient heterogeneous catalysts for the cyanosilylation of aldehydes with trimethylsilyl cyanide at room temperature. The catalytic reactions were optimized by tuning the different reaction parameters (solvent composition, time, catalyst loading) and the substrate scope was also explored. Compound 5 revealed superior catalytic activity leading to up to 75% product yields, while maintaining its original performance upon recycling for at least four reaction cycles. Finally, the obtained herein products represent the unique examples of coordination compounds derived from H3dcna, thus opening up the use of this multifunctional tricarboxylic acid for generating complexes and coordination polymers with interesting structures and functional properties.

Synthesis and magnetic properties of two Mn-based coordination polymers constructed by a mixed-ligand strategy

Two Mn(ii) CPs have been synthesized by mixed-ligand strategy and measured for their magnetic properties. Moreover, analysis of the magnetic structure–effect relationship indicates that 1 and 2 have different Mn chains of magnetic interactions.

Controlling the size of a Zn-MOF through ligand exchange and pore-tailored ZnO assemblies for size-selective gas sensing

The nucleation and final size of Zn-MOF were modulated by ligand exchange, and the annealed ZnO assemblies exhibited size-selective sensing.