Tailoring Polymer-Metal-Organic Frameworks (PolyMOFs) using Telechelic Poly(octenamer)s

Abstract

Polymer-metal-organic frameworks (polyMOFs) represent an unusual class of polymer-MOF hybrids, but inadequate methods for designing and tailoring their underlying polymeric building blocks has been a limitation of these systems. Previous efforts in designing polyMOFs using random copoly(pentenamer)s resulted in a rather limited loading (30%) of benzene-1,4-dicarboxylic acid (H2bdc; a.k.a, terephthalic acid) derived monomers into the polymer ligand. In this context, this study employs poly(octenamer)s that allowed for 100% incorporation of H2bdc containing monomers. This was achieved by homopolymerising a new H2bdc-tagged cyclooctene derivative through a controlled olefin-metathesis polymerisation in the presence of acyclic olefins as chain-transfer agents (CTAs). Using a novel CTA led us to achieve a homopolymer with reversible addition fragmentation chain-transfer (RAFT) telechelics, which was then utilized as macroinitiators to polymerise styrene and produce ABA-type triblock copolymers, wherein a poly(octenamer) block centered between two polystyrene (PS) blocks. Combining these polymers with Zn(II) produced polyMOFs with tunable structural morphologies influenced by the architecture, composition, and monomer content of the polymer ligand. Interestingly, the discrete thermoplastic PS domains enabled the corresponding crystalline polyMOFs to exhibit a reversible glassy-to-rubbery characteristics at >100 °C.