NO2 is one of the most important air pollutant gases for the environment and human health. H2 is seen as the next generation of clean energy to promote sustainable development. However, sensitive detection of NO2 at room temperature is still a major challenge, and reliable H2 sensors are also scarce. Metal oxide semiconductor (MOS) gas sensors are advantageous for detecting gas. Hence, we synthesized the unique hexahedral hollow mesoporous In2O3 (h-In2O3) derived from MIL-68 (In). The formation process and properties of h-In2O3 were analyzed. The surface of h-In2O3 is rich in hydroxyl groups, which are active sites for NO2 adsorption at room temperature. Increasing working temperature up to 160 °C enables effective sensing reaction with H2. Based on different temperature-dependent gas sensing mechanisms, the h-In2O3 sensor exhibits ultrasensitive response values of 400 towards 100 ppb NO2 at room temperature (24 °C) and of 17.99 towards 10 ppm H2 at 160 °C. In addition, the h-In2O3 sensor exhibits reliable linear response, low theoretical detection limit of 1.8 ppt and 23 ppb for NO2 and H2, excellent selectivity, repeatability and long-term stability. The synergistic effect of the unique structure, larger specific surface area, and abundant adsorbed oxygen plus oxygen vacancy contribute to the excellent gas sensing performance of the h-In2O3 sensor. This study provides a promising strategy for the development of bifunctional gas sensors.