Iron(iii) oxyhydroxide and oxide monoliths with controlled multiscale porosity have been successfully fabricated via the sol-gel process accompanied by phase separation. The size of macropores was controlled by synthesis parameters such as starting compositions. The as-dried iron(iii) oxyhydroxide monoliths were amorphous and possessed surface areas over 340 m2 g-1, of which mesostructures could be further controlled by a heat-treatment at 250-350 °C without collapse of macrostructures and monolithic forms. When the as-dried gel was heated at 300 °C, the resultant gel transformed to crystalline α-Fe2O3 and exhibited a specific surface area of 124 m2 g-1. Heat-treatment at 350 °C resulted in the broadened size distribution of mesopores. The adsorption behavior of Congo red has revealed that the interconnected macroporous structure contributed to faster diffusion and better accessibility in a continuous flow-through set up, and the crack-free monolithic forms accounted for an advantageous use of the flow-through adsorbents.