Alternating Zr/Hf Layers as Markers of Crystal Growth in the Metal-Organic Framework UiO-66
Metal-organic frameworks (MOFs), a diverse class of porous crystalline materials comprising metal nodes coordinated to organic linkers, are promising candidates for gas separation, heterogeneous catalysis, drug delivery, and other areas. Controlling particle size, morphology, and reactivity is an important way to tune MOFs for specific applications. To control these properties more systematically, a better understanding of crystal growth mechanisms is needed. In this work, crystalline samples of the MOF UiO-66 were synthesized using alternating spikes of zirconium and hafnium nodes and characterized using scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy. Results identify regions of fastest growth and demonstrate the use of metal identity in elucidating crystal growth mechanisms.