Adsorption of pyridine onto the metal organic framework MIL-101

Pyridine can be adsorbed on coordinative unsaturated sites of MIL-101 formed during dehydration with a high stabilization energy. [Display omitted] ► Quantitative examination of pyridine adsorption on MIL-101. ► Theoretical calculation of the stabilization energy for the pyridine adsorption. ► Discussion on the adsorption site and strength of pyridine on MIL-101. The adsorption of pyridine onto the metal organic framework MIL-101 was investigated by experimental and theoretical methods. The amount of pyridine adsorbed on MIL-101 was extraordinarily large at 20°C, corresponding to about 950mg/g of dried MIL-101 and approximately half of the voids being filled. Most of the pyridine that had filled the voids was rapidly removed by evacuation at room temperature, but some of the pyridine was so strongly adsorbed that it was retained even under evacuation at 150°C. Although IR spectra of the adsorbed pyridine indicated the adsorption of pyridine as pyridinium ions and coordinated pyridine at low temperatures, increasing the adsorption temperature induced partial cleavage of the pyridine rings. The high stabilization energy of pyridine on the coordinative unsaturated sites (CUS) of MIL-101, obtained by theoretical calculation, −103kJ/mol, supported the strong adsorption of pyridine on the CUS.