With industrilization, hazardous organic compounds released into atmosphere and greenhouse gas severely affect the environment. Those environmental concern has dramatically increased interest among researchers. It becomes urgent to degrade organic compounds and reduce carbon dioxide. In this book, a new catalyst with inverse opal structure was introduced and mounted on a monolithic optical fiber reactor. This catalyst was found to increase the reaction rate tremendously by about 2.5 times for organic compound in vapor phase. Also it was successfully applied to reduce carbon dioxide to useful products of industrial significance, methanol and its application in environment was discussed.