Iron(III) Arylhydrazone Complexes Immobilized on Amine‐Functionalized Mesoporous Silica: Catalysts for the Valorization of Biomass‐Derived Furfuryl Alcohol

Abstract

The aquasoluble FeIII complexes [Fe(H2O)3(L1)] ⋅ 4H2O (Fe1) and [Fe(H2O)3(L2)] ⋅ 3H2O (Fe2), bearing the basic forms of 5‐chloro‐3‐(2‐(4,4‐dimethyl‐2,6‐dioxocyclohexylidene)hydrazinyl)‐2‐hydroxy‐benzenesulfonic acid (H3L1) and 3‐(2‐(2,4‐dioxopentan‐3‐ylidene)hydrazinyl)‐2‐hydroxy‐5‐nitrobenzenesulfonic acid (H3L2), were incorporated for the first time into amine‐functionalized SBA‐15 support via an impregnation method. The successful preparation of the composites was confirmed by Fourier‐Transform Infrared spectroscopy (FT‐IR), powder X‐ray diffraction (XRD), scanning electron microscope (SEM/EDS), transmission electron microscopy (TEM), elemental analysis, and nitrogen adsorption‐desorption isotherms. The resulting Fe1@aptesSBA‐15 and Fe2@aptesSBA‐15 composites were tested as the first SBA‐15‐based heterogeneous catalysts for the conversion of furfuryl alcohol under mild reaction conditions (80 to 100 °C) and with an environmentally friendly oxidant (TBHP, 70 % aq. sol. with 1 : 1 oxidant/substrate molar ratio). The influence of various factors, such as reaction time, amounts of oxidant and catalyst, was investigated. The reaction time can be fairly reduced by adopting a microwave‐assisted method allowing it to reach complete conversion after 0.25 h, in the absence of any added solvent or additive. Under these conditions, a vigorous furfuryl alcohol polymerization process occurred, with furfural as a by‐product. Recycling studies were carried out for Fe2@aptesSBA‐15 and after four consecutive runs, the overall conversion of furfuryl alcohol remained high (≥99 %), without an appreciable change in the obtained yield.