Gas effects on the chemical and structural characeristics of porous MoO3 and MoO3−x grown by vapor condensation in helium and hydrogen

▶ Growth of porous MoO3 was promoted in evaporations under 100 Pa of He or H2. ▶ Reducing effect of the gas was evidenced when the hydrogen pressure reached 600 Pa. ▶ The He-grown samples exhibited β-MoO3 while α-MoO3 in the H2-grown samples. ▶ A weak confinement effect is achieved with hydrogen favoring the porous growth.