2H NMR as a Practical Tool for Following MOF Formation: A Case Study of UiO-66

Developing the mechanism for MOF formation is crucial for the rapid development of new materials. This work demonstrates that Deuterium NMR spectroscopy is the optimal inter-laboratory methodology for understanding the in situ kinetics of metal-organic framework (MOF) formation. This method is facile, affordable, and allows for the isolation and monitoring of individual reagents by using one deuterated component while the remaining components are protonated. This study utilizes 2H NMR, via the spectrometer's lock channel, to investigate the formation of UiO-66 as influenced by different modulators: acetic acid, benzoic acid, and hydrochloric acid. By monitoring the concentration of the deuterated linker and observing the chemical shift and peak width of deuterated water over time, key elements of the mechanism are unraveled. Paradoxically, conditions that cause the ligand to be consumed more slowly result in MOFs forming more quickly and with fewer defects. This phenomenon is attributed to the dissociative mechanism associated with the Zr(IV)-containing node.