Photonic hybrid crystals constructed from in situ host-guest nanoconfinement of a light-emitting complex in metal-organic framework pores

We report the concept underpinning the facile nanoconfinement of a bulky luminous guest molecule in the pores of a metal-organic framework (MOF) host, which yields a hybrid host ⊃ guest nanomaterial with tunable opto-electronic characteristics and enhanced photostability. Utilizing an in situ host-guest confinement strategy enabled by molecular self-assembly, we show that the highly emitting ZnQ [Zn-(bis-8-hydroxyquinoline)] guest complexes could be rapidly encapsulated within the sodalite nanocages of zeolitic imidazolate framework (ZIF-8) host crystals. The nature of optical and electronic transitions phenomena of the guest-encapsulated ZIF-8 ⊃ ZnQ has been elucidated by means of fluorescence and absorption spectroscopy measurements, and substantiated further via theoretical molecular orbital calculations revealing the plausible host-guest charge transfer mechanism involved. Evidence suggests that its photophysical properties are not only strongly determined by the host-guest co-operative bonding interactions within the environment of the confined MOF nanocage, but also can be engineered to manipulate its emission color chromaticity or to shield light-sensitive emitting guests against rapid photochemical degradation.