Synthesis, structure and gas adsorption properties of a stable microporous Cu-based metal–organic framework assembled from a T-shaped pyridyl dicarboxylate ligand

Abstract

A three-dimensional microporous metal–organic framework assembled from a T-shaped pyridyl dicarboxylate ligand, 4′-(pyridin-4-yl)-[1,1′-biphenyl]-3,5-dicarboxylic acid (H₂PBPD), has been successfully synthesized via solvothermal reaction with copper(II) nitrate. Compound 1 was characterized by X-ray single-crystal diffraction, elemental analysis, IR spectroscopy and thermogravimetric analyses. Single-crystal X-ray diffraction analysis indicates that compound 1 is a (3,6)-connected three-dimensional framework with the point symbol {4²·6}₂{4⁴·6²·8⁶·10³}. In the framework of this compound, there exist two large metal–ligand cages. Stability tests show that compound 1 keeps its crystal structure after being soaked in several organic solvents or calcined at 250 °C under air atmosphere. The N₂ adsorption at 77 K shows that compound 1 is microporous with a BET surface area of 1682 m² g⁻¹. Compound 1 possesses high adsorption capacities for CO₂ (114 cm³ g⁻¹, 273 K) under ambient pressure. The test of CO₂ cyclic adsorption and regeneration of 1 shows that it has a stable CO₂ adsorption capacity and no obvious weight change after doing this ten times.