Iron(iii) oxyhydroxide and oxide monoliths with controlled multiscale porosity: synthesis and their adsorption performanceElectronic supplementary information (ESI) available: The molecular structure of Congo red; time evolutions of pH in the reaction solution; mesopore size distributions of the as-dried monoliths with varied starting compositions; change in diameter of the monoliths during gelation, drying, and heat treatment processes; macropore size distributions of the monoliths heat treated

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 m 2 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-Fe 2 O 3 and exhibited a specific surface area of 124 m 2 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. Iron( iii ) oxyhydroxide and oxide monoliths with controlled multiscale porosity have been successfully fabricated via the sol-gel process accompanied by phase separation.