Zr(IV) and Ce(IV)-based metal-organic frameworks incorporating 4-carboxycinnamic acid as ligand: Synthesis and properties

Abstract

Two new microporous metal-organic framework materials constructed from Zr(IV) (1) or Ce(IV) (2) ions and 4-carboxycinnamate (CCA) ligand are presented. 1 was prepared by heating a mixture of ZrCl4, H2CCA ligand and acetic acid with a molar ratio of 1:1:10 in N,N′-dimethylformamide (DMF) at 150 °C for 24 h. 2 was synthesized by solvothermal reaction of a mixture of ammonium cerium(IV) nitrate and H2CCA ligand in a DMF/H2O mixture at 100 °C for 20 min. The as-synthesized and the thermally activated forms (1′ and 2′) of the compounds were characterized by X-ray powder diffraction (XRPD), Fourier transform infrared (FT-IR), thermogravimetric (TG) and elemental analysis. 1 and 2 show high thermal stability up to 390 and 300 °C in air atmosphere, respectively. According to XRPD measurements, both compounds show moderate stability in water, but they lose their crystallinity in 1 M HCl. N2 sorption experiments reveal that 1′ and 2′ possess BET surface areas of 870 and 1210 m2 g−1, respectively. The CO2 uptake values of 1′ and 2′ at 0 °C and 1 bar are 2.0 and 1.6 mmol g−1, respectively.