Topochemical polymerizations and crystal Cross-Linking of metal organic frameworks

Abstract

Topochemical polymerizations have been attracting continuous interest as one of the precise polymerizations in a confined space. However, it is still not easy for designing new monomers due to difficulty in designing and controlling the arrangement suitable for topochemical polymerization. In this chapter, we shortly review polymerization in a confined space and demonstrate recent advances in topochemical polymerizations, providing the molecular orientations for various topochemical polymerization monomers. Then, we propose a new type of topochemical polymerization by use of metal organic framework (MOF). MOF is nano-porous crystalline materials constructed by metal ions and rigid organic ligands equipped with two or more ligation sites to form robust 3D host framework with nano-pores. The void space between them is wide and stable, which prompted us to investigate cross-linking of the organic ligands as the host monomers by the external guest monomers by means of two chemical reactions: (1) azide-tagged MOF (AzMOF) cross-linked by multi-alkyne cross-linkers via click reaction and (2) cyclodextrinMOF (CDMOF) cross-linked by diglycidyl ethers. They should be new crystalline-state polymerization, because the cross-linking took place without any movement of the host monomers in the open-host framework.