Metal nanoparticles have been widely used as efficient catalysts for many industrial applications due to their unique properties (high surface area, quantum confinement effect etc.). However, there are several problems existing in the traditional metal nanoparticle catalysts. Activity loss caused by aggregation and poor recyclability are key issues. To solve these problems, efforts have been put on creating materials with new structures. Porous layer coating has been developed as an effective method. The porous layer serves as a protection layer between the nanoparticles to prevent...