Quantitative Analysis of Linker Composition and Spatial Arrangement of Multivariate Metal–Organic Framework UiO-66 through <sup>1</sup>H Fast MAS NMR
Jing Tang, Shenhui Li, Yongchao Su, Yueying Chu, Jun Xu, Feng Deng
Abstract
Fast 1H 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 1H–1H DQ–SQ MAS NMR experiments facilitate the 1H NMR chemical shift assignments. It was demonstrated that the fast 1H MAS technique could improve the resolution of 1H 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 1H–1H spin diffusion homonuclear correlation experiments. The relative intensities of the 1H–1H 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 1H–1H spin diffusion NMR spectra are nearly the same as the corresponding 1D 1H 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.