A Series of new Urea-MOFs Obtained via Post-synthetic Modification of NH2-MIL-101(Cr): SO2, CO2 and H2O Sorption

Abstract

The amino group in the MOF NH2-MIL-101(Cr) was post-synthetically converted into urea-groups partially using either ethyl isocyanatoacetate, furfuryl isocyanate, p-toluenesulfonyl isocyanate or 3-(triethoxysilyl)propyl isocyanate in acetonitrile. The derived four novel urea-MOFs exhibit the expected lower BET surface areas and pore volumes than MIL-101(Cr) and NH2-MIL-101(Cr) MOFs but the partially p-toluenesulfonyl-urea-modified MOF exhibits an outstanding SO2 adsorption capacity of 823 cm3 g−1 (corresponding to 36.7 mmol g−1 or 70 wt.% at T=0 °C and 0.9 bar), which is the second highest SO2 uptake of any known material today – surprisingly even better than for highly porous MIL-101(Cr) with an uptake of 645 cm3 g−1 SO2 under the same conditions. The high uptake is linked to the favorable dipole interactions of SO2 with the sulfonyl group of the p-toluenesulfonyl-modified MOF.