Monoliths are used in a variety of applications, including environmental catalysis, chemical synthesis, and bio-catalysis. In environmental catalysis, they are crucial for exhaust gas treatment in automotive and industrial applications, where they help in the removal of harmful pollutants. In chemical synthesis, monoliths are employed in processes like hydrogenation, oxidation, and reforming reactions. They are also gaining traction in bio-catalysis for enzyme immobilization and biotransformation processes.