Exploring the Photodynamics of a New 2D-MOF Composite: Nile Red@Al-ITQ-HB.

Abstract

In this work, we unravel the photodynamics of Nile Red (NR) interacting with Al–ITQ-HB nanostructure, a new layer-type metal–organic framework (MOF) with potential catalytic and photonic applications. Steady-state spectroscopy reveals the presence of NR monomers and aggregates when interacting with the MOF structure. Time-resolved experiments provide emission lifetimes of the interacting monomers, H- and J-type aggregates. We observed contributions from two monomer populations having different environments. One monomer species emits from the local-excited state and another from a photoproduced charge-separated state resulting from an ultrafast intramolecular charge transfer (ICT). Femtosecond fluorescence experiments reveal that the ICT process occurs in ∼1 ps. Fluorescence microscopy on single crystals and agglomerates of the composites shows a homogenous distribution of the dye lifetimes within the material. This study shows that the photobehavior of NR in Al–ITQ-HB MOF is dictated by its location within the material. The reported findings using a well-known polarity probe and a new two-dimensional MOF provide information on the microenvironment of this material, which may help for designing smart MOFs with potential applications in photonics and nanocatalysis.