The chemistry behind room temperature synthesis of hafnium and cerium UiO-66 derivatives

Abstract

As metal−organic framework (MOF) production scales up to meet industrial needs, the MOF field finds itself looking for less hazardous and more energy efficient synthetic protocols. Effective methods that operate under ambient conditions will be a huge production advantage that can promote MOF industrialization. To deepen our understanding of room temperature (RT) MOF synthesis, we investigate RT formation of Hf and Ce UiO-66 derivatives. We report the first successful RT synthesis of Hf UiO-66-X (X = –COOH, –NO₂, –NH₂, –Br and –(OH)₂) by first forming a hafnium oxocluster at 80 °C in water or 120 °C in DMF and subsequently adding the linker at RT. Further, we present a green, one-step synthesis protocol for Ce UiO-66 derivatives in aqueous media either with or without a modulator. We compare the crystallinity, morphology, and yield of these one-step and two-step RT methods. This study advances current chemical understanding of RT synthesis of Hf and Ce UiO-66 structures and could help material chemists develop green RT synthesis protocols for other MOF structures.