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The combination between photoactive molecules and inorganic structures is of great interest for the development of advanced materials in the field of optics. Particularly, zeotypes with extra-large pore size are attractive because they allow the encapsulation of bulky dyes. The microporous aluminophoshate Mg-ITQ-51 (IFO-type structure) represents an ideal candidate because of the synergic combination of two crucial features: the IFO framework itself, which is composed of non-interconnected one-dimensional extra-large elliptical channels with a diameter up to 11 Å able to host bulky guest species, and the particular organic structure-directing agent used for the synthesis (1,8-bis(dimethylamino)naphthalene, DMAN), which efficiently fills the IFO pores, and is itself a photoactive molecule with interesting fluorescence properties in the blue range of the visible spectrum, thus providing a densely-incorporated donor species for FRET processes. Besides, occlusion of DMAN dye in the framework triggers a notable improvement of its fluorescence properties by confinement effect. To extend the action of the material and to mimic processes such as photosynthesis in which FRET is essential, two robust laser dyes with bulky size, rhodamine 123 and Nile Blue, have been encapsulated for the first time in a zeolitic framework, together with DMAN, in a straightforward one-pot synthesis. Thus, photoactive systems with emission in the entire visible range have been achieved due to a partial FRET between organic chromophores protected in a rigid aluminophosphate matrix.

Styryl dyes are generally poor fluorescent molecules inherited from their flexible molecular structures. However, their emissive properties can be boosted by restricting their molecular motions. A tight confinement into inorganic molecular sieves is a good strategy to yield highly fluorescent hybrid systems. In this work, we compare the confinement effect of two Mg-aluminophosphate zeotypes with distinct pore systems (the AEL framework, a one-dimensional channeled structure with elliptical pores of 6.5 Å × 4.0 Å, and the CHA framework, composed of large cavities of 6.7 Å × 10.0 Å connected by eight-ring narrower windows) for the encapsulation of 4-DASPI styryl dye (trans-4-[4-(Dimethylamino)styryl]-1-methylpyridinium iodide). The resultant hybrid systems display significantly improved photophysical features compared to 4-DASPI in solution as a result of tight confinement in both host inorganic frameworks. Molecular simulations reveal a tighter confinement of 4-DASPI in the elliptical channels of AEL, explaining its excellent photophysical properties. On the other hand, a singular arrangement of 4-DASPI dye is found when confined within the cavity-based CHA framework, where the 4-DASPI molecule spans along two adjacent cavities, with each aromatic ring sitting on these adjacent cavities and the polymethine chain residing within the narrower eight-ring window. However, despite the singularity of this host–guest arrangement, it provides less tight confinement for 4-DASPI than AEL, resulting in a slightly lower quantum yield.

Styryl dyes are generally poor fluorescent molecules inherited from their flexible molecular structures. However, their emissive properties can be boosted by restricting their molecular motions. A tight confinement into inorganic molecular sieves is a good strategy to yield highly fluorescent hybrid systems. In this work, we compare the confinement effect of two Mg-aluminophosphate zeotypes with distinct pore systems (the AEL framework, a one-dimensional channeled structure with elliptical pores of 6.5 Å × 4.0 Å, and the CHA framework, composed of large cavities of 6.7 Å × 10.0 Å connected by eight-ring narrower windows) for the encapsulation of 4-DASPI styryl dye (trans-4-[4-(Dimethylamino)styryl]-1-methylpyridinium iodide). The resultant hybrid systems display significantly improved photophysical features compared to 4-DASPI in solution as a result of tight confinement in both host inorganic frameworks. Molecular simulations reveal a tighter confinement of 4-DASPI in the elliptical channels of AEL, explaining its excellent photophysical properties. On the other hand, a singular arrangement of 4-DASPI dye is found when confined within the cavity-based CHA framework, where the 4-DASPI molecule spans along two adjacent cavities, with each aromatic ring sitting on these adjacent cavities and the polymethine chain residing within the narrower eight-ring window. However, despite the singularity of this host–guest arrangement, it provides less tight confinement for 4-DASPI than AEL, resulting in a slightly lower quantum yield.