Morphology‐Controllable Hexagonal‐Phase Indium Oxide In Situ Structured onto a Thin‐Felt Al 2 O 3 /Al‐Fiber for the Hydrogenation of CO 2 to Methanol

Indium oxide is as a promising catalyst for the hydrogenation of CO 2 to methanol. Previous studies mainly focused on the cubic‐phase In 2 O 3 (C‐In 2 O 3 ), but the hexagonal‐phase In 2 O 3 (H‐In 2 O 3 ) with a corundum structure has been rarely studied because of the difficulty in its synthesis. Herein, the morphology‐controllable H‐In 2 O 3 in situ structured onto a thin‐felt Al 2 O 3 /Al‐fiber is prepared by a facile mixed solvothermal method. The amount of H‐In 2 O 3 is strongly dependent on the urea/In molar ratio during the mixed solvothermal synthesis. The optimal catalyst obtained at a urea/In ratio of 4.5 possesses the highest amounts of oxygen vacancy and strong basic site. Such catalyst achieves a turnover frequency of 47.8 h −1 (the number of CO 2 converted into methanol per oxygen vacancy site per hour) and is stable for at least 200 h, being capable of converting 4.4% CO 2 into methanol at a selectivity of 67.6% at 325 °C (or higher selectivity at the expense of conversion below 325 °C) with a methanol space time yield of 0.20 g MeOH  g cat −1  h −1 . In contrast, the microfibrous‐structured C‐In 2 O 3 (prepared by the incipient wetness impregnation method) delivers a very low methanol selectivity of only 36.8% under identical reaction conditions. In situ Fourier transform infrared spectroscopy experiments reveal that the H‐In 2 O 3 /Al 2 O 3 /Al‐fiber catalyzes CO 2 ‐to‐methanol conversion through formate intermediates.