113Cd Solid-State NMR for Probing the Coordination Sphere in Metal-Organic Frameworks

Spectroscopic techniques are a powerful tool for structure determination, especially if single-crystal material is unavailable. Cd-113 solid-state NMR is easy to measure and is a highly sensitive probe because the coordination number, the nature of coordinating groups, and the geometry around the metal ion is reflected by the isotropic chemical shift and the chemical-shift anisotropy. Here, a detailed investigation of a series of 27 cadmium coordination polymers by Cd-113 solid-state NMR is reported. The results obtained demonstrate that (CdNMR)-Cd-113 is a very sensitive tool to characterize the cadmium environment, also in non-single-crystal materials. Furthermore, this method allows the observation of guest-induced phase transitions supporting understanding of the structural flexibility of coordination frameworks.