Ag(I) coordination polymer of 1,2,4,5-benzenetetracarboxylic acid and thiomorpholine-4-carbonitrile

Abstract

Metal-organic frameworks (MOFs) are regarded as promising materials for applications in catalysis, separation, gas storage and molecular recognition. Here we report the synthesis and characterization of novel silver(I) MOF obtained by the reaction of silver(I) nitrate with 1,2,4,5- benzenetetracarboxylic acid (H4BTEC) and thiomorpholine-4-carbonitrile (tmc). As shown by X-ray difraction analysis, silver(I) centers have distorted tetrahedral geometry with two coordination sites occupied by carboxylic oxygen atoms of two H4BTEC, and the other two by N-atom from nitrile group and S-atom of tmc, respectively. Adjacent silver-carboxylate chains are connected by two tmc ligands into a 2D polymeric structure. Water molecules between these 2D layers are hydrogen bonded to carboxylic groups from adjacent layers and thus expanding the 2D structure into a supramolecular 3D structure. Hydrogen bonds make this structure flexible and suitable for gas absoption. Potential aplication of this coordination polymer as a hydrogen storage material will be the subject of further investigations.

Metal-organske umrežene strukture (engl. Metal organic frameworks, MOFs) predstavljaju potencijalno dobre materijale sa primenom u katalizi, odvajanju, skladištenju gasova i molekulskom prepoznavanju. U ovom radu opisana je sinteza i karakterizacija novog MOF-a srebra(I) dobijenog reakcijom srebro(I)-nitrata sa 1,2,4,5-benzentetrakarboksilnom kiselinom (H4BTEC) i tiomorfolin-4-karbonitrilom (tmc). Rendgenska strukturna analiza je pokazala da srebro(I) centri imaju distorgovanu tetraedarsku geometriju, pri čemu dva koordinaciona mesta zauzimaju atomi kiseonika dva molekula H4BTEC, dok su druga dva koordinacina mesta zauzimaju redom N-atom nitrilne grupe i S-atom tmc-a. Susedni srebro-karboksilatni lanci su povezani preko dva tmc liganda u 2D polimernu strukturu. Između 2D slojeva nalaze se molekuli vode koji grade vodonične veze sa karboksilatnim grupama iz susednih slojeva formirajući supramolekulsku 3D strukturu. Vodonične veze čine ovu strukturu fleksibilnom i pogodnom za apsorpciju gasova. Potencijalna primena ovog koordinacionog polimera za skladištenje vodonika će biti predmet daljih istraživanja.