Exploring RE-MOFs with spn Topology and their Stimuli-Responsive Structural Properties

The work described herein explores an emerging class of metal–organic frameworks (MOFs) that are synthesized using rare-earth (RE) metals, known as RE-MOFs. In this work, these RE-MOFs are comprised of RE-hexanuclear clusters and tritopic organic linkers that give rise to a framework with spn topology. This thesis explores the (i) design, synthesis, and characterization of a yttrium (Y(III)) hexanuclear-cluster based RE-MOF, known as CU-45 (CU = Concordia University, experiment 45), (ii) the implementation of neodymium oxide (Nd2O3) precursors as templating agents, and (iii) the design, synthesis, and characterization of terbium and europium (Tb(III) and Eu(III)) MOFs with preliminary exploration of luminescence properties for potential sensing applications. Chapter 2 explores the synthesis, characterization, and stimuli-responsive structural transformation of CU-45. CU-45, an achiral MOF, is exposed to various external stimuli including pressure, pH, temperature, and solvent, and in each case undergoes a phase transformation to give a chiral, RE-chain based MOF, known as Y-MOF-76. The physical and chemical properties of CU-45 and Y-MOF-76, as well as the underlying mechanism of the stimuli-responsive structural transformation is discussed. Chapter 3 aims to address and improve the stability of CU-45, first by exploring a phenomenon known as lanthanide templating, which can facilitate the assembly and stabilization of lanthanide clusters. By adding a Nd2O3 precursor template to the CU-45 synthetic mixture, a phase pure MOF with improved crystallinity can be obtained. Furthermore, the effect of incorporating other rare-earth ions in CU-45, including Tb(III)- and mixed-metal Tb(III)/Eu(III)-CU-45, on stability is examined