Catalytic synthesis of iron-doped graphitic aerogels from poly(phloroglucinol-terephthalaldehyde – urethane) precursors

Abstract

We report a new class of graphitic carbon aerogel precursors based on iron oxide-doped poly(phloroglucinol-terephthalaldehyde–urethane) (T-POL/PU-FeOx) networks. The hybrid polymeric network incorporates a rigid aromatic triisocyanate, tris(4-isocyanatophenyl)methane, which reacts in situ with the hydroxyl groups of phloroglucinol to form a polyurethane-containing framework. Monolithic aerogels derived from this system undergo catalytic graphitization at significantly reduced temperatures (800–1500 °C) compared to conventional graphitization (2500–3300 °C). An oxidative ring fusion aromatization step (240 °C, air) prior to pyrolysis enhanced the degree of graphitization. The resulting graphitic aerogels were characterized by XRD, Raman spectroscopy, TGA, TEM, SEM, XPS, and N₂ sorption porosimetry. Compared to their purely phenolic analogs, graphitic carbons derived from the polyurethane-containing precursors exhibited enhanced porosity and higher surface areas. Optimal graphitization was achieved at 1500 °C, yielding aerogels primarily composed of 100 % (w/w) graphitic carbon. During pyrolysis, iron oxides facilitated carbothermal reduction to form Fe(0) nanoparticles embedded within the carbon matrix. These materials can find applications ranging from catalysis (e.g., oxygen reduction reaction - ORR) to biomedical applications (drug delivery). Additionally, none of the procedures for preparing these materials caused significant damage to the monoliths, making these materials useful for form-factor dependent applications.