Porous coordination polymers show great potential in applications, such as heterogeneous catalysis, biomedical applications, sensor technology, magnetism, adsorption, separation and storage of gases due to their structural properties, namely: high regularity, tunable pore sizes, and large surface area. Three-dimensional Cu(II)-based coordination polymers were obtained using Cu(ClO4)x6H2O or Cu(BF4)x6H2O salts and different exo-bidentate bipyridine-based ligands, such as: 1,2-bis(4-pyridyl)ethane (bpa), 1,2-bis(4-pyridyl)ethylene (bpe), and 4,4’-azopyridine (azopy). The synthesized compounds have the general formula {[Cu3(CO3)2(L)3](Y)2}n, where L = bipyridine-based ligand and Y = ClO4- or BF4- anions. Single-crystal and powder X-ray diffraction along with spectroscopic techniques, such as FTIR and UV-Vis in solid state, as well as elemental and thermal analyses were used in characterization of these compounds. All obtained compounds are isostructural. The 2-D Kagomé layers are formed, in the basic ammonia solution, by direct fixation of atmospheric CO2 as carbonate anion and are stacked one onto another, connected via the bipyridine-based ligands, forming hexagonal channels. Disordered counter anions are found along the channels. The aqueous ammonia solution was used with multipurpose - stabilising solutions of the reagents which precipitate out in water, acting as a source of hydroxide for carbonate formation conducting to chemical sequestration of atmospheric CO2, and as a means of controlling structure and dimensionality in coordination polymers. The influence of the organic ditopic ligands used as pillars between the 2-D Kagomé layers on the size of the formed cavities, as well as the adsorption properties of these compounds are discussed.

Crystalline porous copper(II) coordination polymers with pillared Kagomé layers

ACS Fall 2021

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