α-Bi2O3 was synthesized via a hydrothermal method at 180 °C for 12 h in 1 (S1) and 2 (S2) M KOH aqueous solutions, using Bi(NO3)3•5H2O as raw material. The synthesized material was characterized by X-ray powder diffraction (XRPD) technique. The XRPD results indicated that by using 1M KOH aqueous solution, α-Bi2O3 was obtained with small fractions of β-Bi2O3, while 2M KOH solution resulted in pure α-Bi2O3. The α-Bi2O3 was crystallized in a monoclinic crystal structure with space group of P21/c. The size and morphologies of the synthesized material was studied by field emission scanning electron microscope (FESEM). The FESEM images showed that the obtained material had multigonal structures in micron dimensions. The synthesized material was tested as catalyst in Biginelli reactions and excellent performance was achieved in the optimized conditions. Experimental design was used to obtain optimized reaction conditions. Also the optical properties of the obtained material were studied by ultraviolet visible (UV-Vis) diffuse reflectance spectrum (DRS). Manuscript profile