Shape-Defined Hollow Structural Co-MOF-74 and Metal Nanoparticles@Co-MOF-74 Composite through a Transformation Strategy for Enhanced Photocatalysis Performance.

In recent years, metal-organic frameworks (MOFs) have received extensive interest because of the diversity of their composition, structure, and function. To promote the MOFs' function and performance, the construction of hollow structural metal-organic frameworks and nanoparticle-MOF composites is significantly effective but remains a considerable challenge. In this article, a transformation strategy is developed to synthesize hollow structural Co-MOF-74 by solvothermal transformation of ZIF-67. These Co-MOF-74 particles exhibit a double-layer hollow shell structure without remarkable shape change compared to original ZIF-67 particles. The formation of hollow structure stemmed from the density difference of Co between ZIF-67 and Co-MOF-74. By this strategy, hollow structural Co-MOF-74 with different sizes and shapes are obtained from corresponding ZIF-67, and metal nanoparticles@Co-MOF-74 is synthesized by corresponding nanoparticles@Co-ZIF-67. To verify the structural advantages of hollow structural Co-MOF-74 and Ag nanoparticles@Co-MOF-74, photocatalytic CO reduction is used as a model reaction. Conventionally synthesized Co-MOF-74 (MOF-74-C), hollow structural Co-MOF-74 synthesized by transformation method (MOF-74-T) and Ag nanoparticles@Co-MOF-74 (AgNPs@MOF-74) are used as cocatalysts in this reaction. As a result, the cocatalytic activity of MOF-74-T and AgNPs@MOF-74 is 1.8 times and 3.8 times that of MOF-74-C, respectively.