Mechanochemistry-assisted encapsulation of metal nanoparticles in MOF matrices via a sacrificial strategy

Abstract

Metal–organic framework (MOF)-supported metal nanoparticle (MNP) composites, especially those with encapsulation structures (MNPs@MOF), hold significant promise for versatile applications. Massive efforts have been devoted towards the preparation of these composites; however, the poor stability of MOFs and their homogeneous growth in solution make these synthetic strategies complex and tedious; this greatly hampers their practical application. Herein, a general mechanochemistry-assisted encapsulation approach was developed to entrap MNPs in MOF matrices. In this approach, metal precursor-supported MNP hybrids were in situ sacrificed to form MNPs@MOF composites via simple ball milling, and the MNPs were encapsulated in the MOF matrices in the solid state during the sacrificial process. This method completely avoids the homogeneous growth of MOFs; furthermore, this approach proceeds with trace amounts of solvents and does not require stabilizing agents; this enables a clean and sustainable synthesis. By this facile approach, many interesting MNPs@MOF composites were prepared. All the composites showed good crystalline structures, and no obvious damages to the MOF were observed. Moreover, in these structures, small MNPs were well encapsulated in the MOF matrices and mainly distributed near the surface of the MOFs, resulting in high catalytic activity and selectivity for the hydrogenation of olefins. Moreover, the MNPs@MOF composites can be easily synthesized on a gram-scale (8 g of Pd@ZIF-8); this achievement would advance their practical application.