Effects of varying water adsorption on a Cu3(BTC)2 metal–organic framework (MOF) as studied by 1H and 13C solid-state NMR spectroscopy

Abstract

The process of water adsorption on a dehydrated Cu₃(BTC)₂ (copper (II) benzene 1,3,5-tricarboxylate) metal–organic framework (MOF) was studied with ¹H and ¹³C solid-state NMR. Different relative amounts of water (0.5, 0.75, 1, 1.5, 2, and 5 mole equivalents with respect to copper) were adsorbed via the gas phase. ¹H and ¹³C MAS NMR spectra of dehydrated and water-loaded Cu₃(BTC)₂ samples gave evidence on the structural changes due to water adsorption within the MOF material as well as information on water dynamics. The analysis of ¹H spinning sideband intensities reveals differences in the ¹H–^63/65Cu hyperfine coupling between dehydrated and water-loaded samples. The investigation was continued for 60 days to follow the stability of the Cu₃(BTC)₂ network under humid conditions. NMR data reveal that Cu₃(BTC)₂ decomposes quite fast with the decomposition being different for different water contents.