Organometallic "sponge" can adsorbe carbon dioxide and nitrogen, study finds
RUDN University chemists together with colleagues from Australia, Iran, Poland, Russia, and Turkey have created a highly porous organometallic polymer. Due to its structure, it is able to hold and store carbon dioxide and nitrogen molecules. The results are published in Inorganica Chimica Acta.
Coordination polymers are hybrid crystalline coordination compounds formed by organic ligands and metal bridges in one, two, or three dimensions due to the formation of a metal-ligand coordination bond. Their main feature is that small fragments can independently assemble into complex structures due to the formation of metal-ligand bonds. They can be one-dimensional (like a long chain of beads), two-dimensional (like lace), or three-dimensional (like building scaffolding). Until now, there were only three similar organometallic polymers with cobalt atoms connected to fragments of pyridine and hydrazine as a ligand. All of them did not have a porous structure. At the same time, especially close attention of scientists is attracted by organometallic coordination polymers, which have a microporous structure and can work as a sponge for gases and other substances. This, for example, simplifies the storage and transportation of gas fuel or protects the environment from carbon dioxide emissions from power plants. RUDN University chemists together with colleagues from Australia, Iran, Poland, Russia, and Turkey have created a new organometallic coordination polymer that is able to retain carbon dioxide and nitrogen in its pores.
"Porosity of metal-organic frameworks dictates one of their most outstanding, but not limited, practical applications for gas storage and separation. However, the ability to predict and control the supramolecular assembly of molecules still remains a challenge, and much more work is required to understand the inter- and intramolecular forces that determine the patterns of molecular structure and crystal packing.", said Fedor Zubkov, Ph.D., Associate Professor at RUDN University's Department of Organic chemistry.
Chemists obtained a new coordination polymer by studying cobalt complexes with ligands containing pyridine and hydrazine residues. Pyridine is an organic substance with one of the carbon atoms of the benzene ring replaced by a nitrogen atom. Hydrazine is two ammonia molecules connected by a nitrogen-nitrogen bond. The new polymer was obtained on the basis of a combination of these two substances and an inorganic salt potassium thiocyanate. The ligand was added to a methanol solution of cobalt sulfate and mixed at room temperature for a long time. A few days later, a green precipitate was formed, from which plate-like polymer crystals were formed. Some of them were studied by chemists using X-ray diffraction analysis, which made it possible to describe its characteristics in detail.
The new polymer has many large pores with a size of about 63 angstroms. One such cavity can fit about 20 molecules of carbon dioxide or 40 molecules of nitrogen. There are so many pores that the surface area of one gram of polymer reaches 30 square meters. Thanks to this structure, each gram of polymer can retain up to 30 cubic centimeters of carbon dioxide under normal conditions. In addition, the new polymer has paramagnetic properties, that is, it is able to be magnetized under the influence of an external magnetic field.
"We found that the resulting complex is able to adsorb nitrogen and carbon dioxide. It can become a new porous coordination polymer for specific binding and storage guest molecules", said Fedor Zubkov, Ph.D., Associate Professor at RUDN University's Department of Organic chemistry.
More information:
Burak Ay et al. A novel paramagnetic coordination polymer, fabricated from Co(NCS)2 and 2-pyridinecarbaldehyde isonicotinoylhydrazone, Inorganica Chimica Acta (2021). DOI: 10.1016/j.ica.2021.120335
Provided by RUDN University
