Highly emissive metal-organic framework composites by host-guest chemistry

The unique host-guest chemistry of metal-organic frameworks (MOFs) can be used to implement additional properties by loading the cavities with functional molecules or even nanoparticles. We describe the gas-phase loading of MOFs featuring either a three-dimensional (MOF-5, MOF-177 and UMCM-1) or one-dimensional channel system (MIL-53(Al)) with the highly emissive perylene derivative N,N-bis(2,6-dimethylphenyl)-3,4:9,10-perylene tetracarboxylic diimide (DXP) or an iridium complex, (2-carboxypyridyl)bis(3,5-difluoro-2-(2-pyridyl)phenyl)iridium(III) (FIrpic). The resulting host-guest composites show strong luminescence, with their optical properties being dominated by the guest species. DXP-loaded MOFs exhibit a high stability towards guest displacement by solvent molecules, while the interaction of FIrpic with the host is weaker. The emissive properties of intercalated DXP also indicate host-guest interactions such as caging effects, strong quenching of the MOF host emission, as well as aggregate formation.