Interrogating the Behaviour of a Styryl Dye Interacting with a Mesoscopic 2D-MOF and Its Luminescent Vapochromic Sensing

Abstract

In this contribution, we report on the solid-state-photodynamical properties and further applications of a low dimensional composite material composed by the luminescent trans-4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM) dye interacting with a two-dimensional-metal organic framework (2D-MOF), Al-ITQ-HB. Three different samples with increasing concentration of DCM are synthesized and characterized. The broad UV-visible absorption spectra of the DCM/Al-ITQ-HB composites reflect the presence of different species of DCM molecules (monomers and aggregates). In contrast, the emission spectra are narrower and exhibit a bathochromic shift upon increasing the DCM concentration, in agreeance with the formation of adsorbed aggregates. Time-resolved picosecond (ps)-experiments reveal multi-exponential behaviors of the excited composites, further confirming the heterogeneous nature of the samples. Remarkably, DCM/Al-ITQ-HB fluorescence is sensitive to vapors of electron donor aromatic amine compounds like aniline, methylaniline, and benzylamine due to a H-bonding-induced electron transfer (ET) process from the analyte to the surface-adsorbed DCM. These findings bring new insights on the photobehavior of a well-known dye when interacting with a 2D-MOF and its possible application in sensing aniline derivatives.

Interrogating the nature of aggregates formed in a model azine based ESIPT coupled AIE active probe: stark differences in photodynamics in the solid state and aggregates in water

“…Considering the J-aggregates show longer emission lifetimes, τ 1 and the τ 2 components were assigned to be from the H- and J-aggregates respectively based on previous reports. 8,57…”

“…Such observations definitely led to the assumption of multiple aggregates having differing emission properties co-existing in the ground state. [53][54][55][56][57] To verify this, the absorption spectrum in the solid state was deconvoluted using Origin s 2019 software (Fig. 6A).…”

Novel Approach for Detecting Vapors of Acids and Bases with Proton-Transfer Luminescent Dyes Encapsulated within Metal–Organic Frameworks

“…The exposition of the HPTS@UiO-66 material to a saturated atmosphere of Et 3 N causes a spectacular change in its emission spectrum (Figure a). After just 2 min of interaction, the emission of the material redshifts a total of 65 nm (∼2900 cm –1 , from 440 to 505 nm), reflecting the super-fast response and efficiency of this material to detect vapors of Et 3 N. Then, a prolonged exposure to Et 3 N (4–60 min) induced an augmentation of the emission intensity of the band at 505 nm of HPTS@UiO-66, making this material even more special, as most of the reported examples of luminescent MOF sensors are based on the quenching of the emission intensity, ,− while those reporting a sensing mechanism with an increase in the luminescence intensity are less frequent . Generally, the increase in the luminescence intensity or the shift in the emission wavelength is highly preferred for developing luminescent sensors, as those which are based on the quenching of the emission intensity may suffer from undesired effects (e.g., photodegradation).…”

“…Metal organic frameworks (MOFs), a class of porous crystalline inorganic–organic hybrid materials, have been postulated as one of the most promising materials for sensing a vast number of different chemical compounds. − Their accessible porosity allows the diffusion of gases, VOCs, or molecules within their structure, favoring possible chemical interactions, and therefore inducing physical or chemical changes in their properties, that can be measured to quantify the amount of the analyte. A special subclass of MOFs that has gained much attention is the luminescent MOFs (LMOFs), which, in few words, are those MOFs capable of emitting light. − This type of LMOF has been widely employed in different scientific fields and potential technological applications such as cell bioimaging, − light-emitting devices, − anticounterfeiting or reversible writing and encoding, − and chemical detection. − Even though the number of LMOFs used for chemical sensing is rather elevated, most of these examples are based on the detection of chemicals in solutions; however, the detection of chemical compounds in the vapor phase is more scarce. ,− Hence, it is paramount to develop novel LMOF alternatives that enable the detection of chemical compounds in the vapor phase and that can be implemented in the development of sensors for being used in several industrial processes.…”

Unraveling the Optimal Cerium Content for Boosting the Photoresponse Activity of Mixed-Metal Zr/Ce-Based Metal–Organic Frameworks through a Photodynamic and Photocurrent Correlation: Implications on Water Splitting Efficiency

“…Metal–organic frameworks (MOFs), a special class of crystalline porous materials constructed with metals ions or clusters interlinked by organic ligands, have attracted the attention of a large number of multidisciplinary researchers owing to their potential implementation in forefront technologies and scientific advancements. − The chemical versatility of these materials has boosted the fabrication of different MOF structures with bespoke physicochemical properties. Indeed, nowadays it is possible to design photoactive MOFs on demand, , which have been used in different fields of photonics spanning from sensing, optoelectronic applications, cell imaging, and photocatalysis. − Due to their large surface area, ordered porous structure, tunable organic bridging linker/metal clusters, higher thermal stability, and better water tolerance than most of other MOFs, Zr-based MOFs isostructural to the UiO family, have garnered great interest for their potential as photocatalysts in different reactions. − However, the UiO-type MOFs are mainly constituted by d 0 metals such as Zr or Hf, whose binding energy is too low, and consequently, the overlap between their orbitals and the π*-orbitals of the organic linkers is very inefficient. , This mismatch in the orbital levels hinders an efficient generation of long-lived charge-separated states (CSSs) in the photoexcited MOFs, which are the cornerstone of the photocatalytic reactions, and therefore reduces the photocatalytic activity of MOFs like Zr-UiO or Hf-UiO . To circumvent this drawback, it has been proposed that doping the Zr clusters with Ce in UiO-isostructural MOFs may enhance the photocatalytic activity as a result of a more efficient ligand-to-cluster charge transfer (LCCT) process upon photoexcitation of the organic linkers. − The enhancement of the LCCT event is caused by the low-lying empty 4f orbitals of Ce 4+ that better overlap with the π*-orbitals of the organic linkers .…”