One-Step Solvent-Assisted Cation Exchange Approach to Hollow Metal-Organic Frameworks Nanoreactors with Orderly Distributed Active Sites for Tandem Catalysis.

Biological membrane-enclosed organelles, in which cascade reactions promoted by multiple enzymes occur, have inspired widespread interest in the design of spatially confined nanoreactors for tandem catalytic transformations. Because of their accessible compartmentalized environments and large framework diversity, hollow metal-organic frameworks (H-MOFs) are ideal platforms for the development of new multi-functionalized nanoreactors. However, simple methodologies for fabrication of hollow MOFs, which possess functionalities that are precisely localized and encapsulated of active sites like those found in biological membrane-enclosed organelles, is a considerable challenge. Herein, a facile, one-step solvent-assisted cation exchange method was firstly developed for controlled synthesis of multifunctional H-MOF, Pd@H-UiO-66-NH, which contains precisely encapsulated Pd nanoparticles (NPs) inside cavities. Micro-mesoporous shell thicknesses in the range of 22-73 nm are effectively controlled by easily tuning Pd loading. Impressively, the delicate nanoarchitecture and precise encapsulation of Pd NPs give Pd@H-UiO-66-NH a propensity for size-selective molecular recognition in catalytic hydrogenation reactions and ability to catalyze tandem processes. Observations made in this effort suggest that one-step solvent-assisted cation exchange protocol might serve as general avenue for the design and construction of multi-functionalized H-MOFs, which can be employed in diverse applications in the fields of material chemistry.