Polymerization-Induced Colloid Assembly Route to Iron Oxide-Based Mesoporous Microspheres for Gas Sensing and Fenton Catalysis

Iron oxide materials have wide applications due to their special physicochemical properties; however, it is a great challenge to synthesize mesoporous iron oxide-based microspheres conveniently and controllably with high surface area, large pore volume, and interconnected porous structures. Herein, mesoporous α-Fe2O3-based microspheres with high porosity are synthesized via a facile polymerization induced colloid assembly method through polymerization of urea–formaldehyde resin (UF resin) and its simultaneously cooperative assembly with Fe(OH)3 colloids in an aqueous solution, followed by subsequent thermal treatment. Remarkably, by controlling the cross-linking degree of UF, pure mesoporous α-Fe2O3 and α-Fe2O3/carbon hybrid microspheres can be synthesized controllably, respectively. They exhibit a uniform spherical morphology with a particle size of around 1.0 μm, well-interconnected mesopores (24.5 and 8.9 nm, respectively), and surface area of 54.4 m2/g (pure mFe2O3 microspheres) and 144.7 m2/g (hybrids), respectively. As a result, mesoporous pure α-Fe2O3 microspheres exhibited excellent H2S sensing performance with a good selectivity, high response to low concentration H2S at 100 °C, and quick response (4 s)/recovery (5 s) dynamics owing to the high surface area, open mesopores, and crystalline structure of the n-type α-Fe2O3 semiconductor. Moreover, mesoporous α-Fe2O3/carbon hybrid microspheres were used as a novel Fenton-like catalyst for the decomposition of methylene blue in a mild condition and exhibit quick degradation rate, high removal efficiency (∼93% within 35 min), and stable recycling performance owing to the synergetic effect of a high surface area and the carbon-protected α-Fe2O3.