Previously reported magnetic properties of the metal organic framework (MOF) and tunable molecular magnet, Cu9X2(cpa)6,-- abbreviated CPA -- have shown this material to be a candidate for enhanced magnetocaloric effect (MCE) and quantum spin liquid (QSL) studies. The robust structure and magnetic topology of the Triangulated Kagome Lattice (TKL) within CPA presents opportunities to tailor its MCE via chemical modifications for application in cryogenic adiabatic demagnetization refrigeration. Similarly, chemical modifications could also alter the highly degenerate ground state, leading to novel opportunities to study QSL physics. Our previous investigations have reported the synthetic tunability of CPA; specifically, insertion and intercalation of 3d and 4f metals and anion substitution within CPA. Here we report the confirmation and limitations of anion substitution in CPA using Powder X-Ray Diffraction (PXRD) as well as newly proposed chemical modifications using solvents inside the crystalline channels (nearly 40% of unit cell volume is “liquid” solvent); a chemistry that lies at the interface of solid and liquid chemistry. The effects of polar and nonpolar solvents on crystal morphology and structural stability of CPA were characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) in conjunction with PXRD to confirm limits of stability for the CPA crystal structure. We also recognize the current multistep synthesis for CPA presents limitations on crystal size and tunability. Following the lead of current work with other macromolecular materials and protein crystal growth, the crystals of CPA should benefit from crystal growth under conditions of microgravity. This, however, presents a synthetic challenge. Engineering a reactor chamber for crystal growth aboard the International Space Station (ISS) is complicated by the multistep synthesis of CPA. Developing a “one-pot” synthesis for CPA by first isolating a stable form of the ligand would be a preferred method. Our attempts to date will be discussed. More generally, a successful one-pot synthesis could also provide an easier path to variants of CPA crystals and compositions, expanding this class of tunable materials for further studies involving the MCE as well as the fundamental physics of QSLs.

Thermochemical characterization of synthetic strategies for the triangulated kagome lattice (TKL) material Cu9X2(cpa)6

2019 Spring National Meeting

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