Structural and Sorption Characteristics of Silica Aerogel Loaded with Flufenamic Acid

This study investigates the structural and sorption characteristics of a composite material consisting of silica aerogel loaded with flufenamic acid (FFA) using various nuclear magnetic resonance (NMR) techniques. Magic angle spinning (MAS) NMR spectroscopy reveals significant interactions between the aerogel matrix and FFA molecules. Solid-state ^29Si NMR provides insights into the stability of the aerogel, while ^1H and ^13C NMR confirm the presence of FFA, highlighting signals from FFA molecules alongside tetraethoxysilane (TEOS) groups. Ethanol-induced desorption of FFA narrows spectral lines, indicating the breaking of intermolecular hydrogen bonds. ^19F MAS NMR spectra show alterations in the local environments of FFA upon loading into the aerogel pores. The evaluation of CO2 sorption characteristics using ^13C NMR demonstrates a slower sorption rate for the AG + FFA composite compared to pure AG, attributed to a decrease in pore volume. Additionally, nuclear Overhauser effect spectroscopy (NOESY) is employed to explore the conformational behavior of FFA within the aerogel matrix, revealing shifts in conformer populations, particularly regarding the rotation of cyclic fragments. These findings offer valuable insights into the structural and sorption characteristics of the AG + FFA composite, contributing to the development of novel drug solid forms. Please see full text https://doi.org/10.1039/D4CP03217A