Mesoporous -Al2O3 powders with nanofiber and nanorod-like structures were synthesized using boehmite sols in the presence of triblock copolymer, P123 in ethanol by solvothermal process at different temparatures (100 degrees C-165 degrees C) followed by calcination at 400 degrees C-1000 degrees C. The powders were characterized by low- and wide-angle X-ray diffraction (XRD), N2 adsorption-desorption, and transmission electron microscopy (TEM). The adsorption efficiency of the powders with Congo red (CR) was studied by UV-vis spectroscopy. The -Al2O3 phase became stable up to 1000 degrees C. The nanorods obtained at 165 degrees C had narrower pore size distribution (PSD) than nanofibers synthesized at 100 degrees C, the former showed higher CR adsorption efficiency. The stepwise growth mechanism of nanofibers to nanorods conversion with increase in solvothermal temperatures was illustrated.