Probing Ce- and\nZr-Fumarate Metal–Organic Framework\nFormation in Aqueous Solutions with In Situ Raman Spectroscopy and\nSynchrotron X‑ray Diffraction

The synthesis of Ce-fumarate and Zr-fumarate metal–organic\nframework (MOF) is monitored for the first time with in situ Raman\nspectroscopy in custom-built solvothermal reactors. Several synthesis\nconditions were explored for Ce-fumarate at room temperature. The\nuse of the method for high-temperature synthesis of Zr-fumarate is\nalso demonstrated. In situ Raman monitoring provided insights into\nboth the solution and crystalline phases of the reaction medium, revealing\nthe dynamic interplay among precursors, modulators, and the forming\nMOF structure. The reaction kinetics was determined by following the\ncharacteristic peak at 1666 cm<sup>–1</sup>. The conversion\nwas in good agreement with the reaction kinetics determined via in\nsitu synchrotron powder diffraction. The resulting MOF products were\nfurther characterized using ex situ X-ray powder diffraction, scanning\nelectron microscopy, thermogravimetry, and surface area measurements.\nThis study demonstrates a simple and industrially scalable method\nfor monitoring MOF synthesis in situ, which can provide insights into\nthe stages and mechanisms of formation of MOFs and other compounds.