Nanocatalysts encapsulated in metal-organic frameworks: Size control and positive influences

Beyond traditional porous materials, metal-organic frameworks (MOFs) have attracted considerable attention for fabricating encapsulated nanocatalysts in the pores/cavities/channels of MOFs due to the high surface area, porous structure, and a large variety of organic linkers. As the host for nanocatalyst encapsulation, MOFs can provide uniform hierarchical pores and channels that can accelerate the mass transfer and migration of reactants or products and various metal‑oxygen clusters and organic linkers, which may interact strongly with nanocatalysts. Herein, state-of-the-art advancements in the encapsulation of nanocatalysts, including catalyst nanoparticles, clusters, quantum dots, and single-atom catalysts, have been summarized. The synthetic methods for nanocatalysts in MOFs and the enhanced properties are especially discussed. Then, positive effects upon the encapsulation of nanocatalysts in MOFs, including tunable chemical environment and encapsulation effects have been explored. Notably, the catalytic activity and product selectivity can be much improved by regulating the chemical environment around nanocatalysts and the interaction between the active nanocatalysts and metal nodes or organic linkers. Finally, challenges and future perspectives in encapsulated nanocatalysts in MOFs are proposed. This review could shed light on the construction of stable nanocatalysts encapsulation in MOFs with maximum exposed active sites and excellent activity in significant reactions.