Rapid-photo-responsive photoluminescence of spiropyran-encapsulated cage-like zeolitic imidazolate frameworks via dynamic energy transfer process

Abstract

The development of photo-responsive fluorescent materials with rapidly switching performance is crucial for many optical applications. Here, we present a novel strategy that enables fast multicolor switching by encapsulating a luminescent dye (acriflavine, AF) and a photochromic molecule (spiropyran, SP) into the cage-like Zeolitic Imidazolate Frameworks (ZIF-11 and rho-ZMOF). Under UV light (365 nm) irradiation, the large conformational freedom of the ZIFs’ pores promotes the rapid conversion of SP from a non-fluorescent closed-ring form to a red-fluorescent open-ring merocyanine (MC) form. Furthermore, this confined space facilitates dynamic fluorescence resonance energy transfer (FRET) between AF and MC. Notably, compared with RHO-ZMOF, the smaller cages of ZIF-11 force the energy donor (AF) and the energy acceptor (SP) into close proximity, leading to dynamically higher efficient FRET (≈ 60.77%). As a result, the dynamic photoluminescence of ZIF-11⊃dyes can be regulated rapidly, efficiently and reversely under UV light (365 nm) and visible light (> 405 nm) irradiation. We also demonstrated that this material can be applied directly in advanced information encryption. This design strategy, utilizing the confined environment of the ZIF's cages, provides a prototype for constructing rapid dynamic energy transfer and dynamic photoluminescent materials.