Millimeter-scale magnetic spherical metal-organic framework core-shell structured composites for recyclable catalytic applications

A facile in situ growth approach for preparing magnetic spherical activated carbon (MSAC)-metal organic framework (MOF) core-shell composite beads with millimeter size is described. This approach overcomes the challenge of processing MOF nanoparticles into shaped bodies with fast magnetic responsivity. The size of the MOF@MSAC beads can be easily tuned by changing the activated carbon core size. Furthermore, the thickness of the MOF shell can be designed by controlling the assembly cycle number and the precursor concentration of forming the MOF. In addition, different types of MOF, including monometallic (e.g., ZIF-67 and HKUST-1) as well as bimetallic ones (e.g., CoZn-ZIF) can be successfully self-assembled to form the shell. As a model catalyst, ZIF-67@MSAC displays satisfying activity in the Knoevenagel condensation reaction, good recyclability and remarkable convenience in separation and recovery. The applicability of the catalyst is contributed to its unique structural features, such as nanoscale active MOF, magnetic responsivity and the dispersing and stabilizing effects of the activated carbon support.