Quantitative Analysis of Linker Composition and Spatial Arrangement of Multivariate Metal-Organic Framework UiO-66 through 1H Fast MAS NMR

Fast H-1 magic-angle spinning (MAS) solid-state NMR spectroscopy was utilized for quantitative analysis of the linker composition and spatial arrangement of functional groups of MTV-UiO-66-(BDC-CH3)(x)-(BDC-OH)(y)-(BDC-NH2)(1-x-y). 2D H-1-H-1 DQ-SQ MAS NMR experiments facilitate the H-1 NMR chemical shift assignments. It was demonstrated that the fast H-1 MAS technique could improve the resolution of H-1 NMR spectra and allow the quantitative determination of the relative content of functional linkers without acid-digested treatment of MTV-UiO-66. The spatial proximities of various components including BDC-CH3 and BDC-OH were verified from the 2D H-1-H-1 spin diffusion homonuclear correlation experiments. The relative intensities of the H-1-H-1 spin-diffusion buildup curves via OH -> CH3 and CH3 -> OH pathways were closely related to the linker composition of MTV-UiO-66. Additionally, the extracted slices along with the CH3 site and OH site from the 2D( 1)H-H-1 spin diffusion NMR spectra are nearly the same as the corresponding 1D H-1 MAS NMR spectra, indicating that the three functional linkers are in approximately random distribution in MTV-UiO-66-A and MTV-UiO-66-B. This work provides an efficient approach to examine the spatial arrangement of MTV-MOFs containing three distinct linkers.