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Phillipsite was crystallized from a high siliceous aluminosilicate mixture containing Zn cations and methylene blue (MB). The presence of MB did not affect the crystallization, but it resulted in a substantial amount of dye being anchored to the zeolite, despite its narrow channels. Dye-free synthetic phillipsite modified with MB solution showed markedly lower dye content, which, however was considerably higher than those in the MB-treated natural phillipsite and mordenite. The ultra violet/visible (UV-vis) spectra of the dye-modified synthetic phillipsites indicated the presence of MB monomers and oligomers, whereas the spectra of the modified natural zeolites showed protonated MB also. The electron spin resonance spectra of samples crystallized with MB indicated the presence of paramagnetic species. [ABSTRACT FROM AUTHOR]

Abstract: Zeolite losod prepared with tetrabutylammonium hydroxide was applied as matrix for sulfur anion-radicals thermally generated from precursors (elemental sulfur and alkalis or alkaline oligosulfides). We hoped that large los cages could favor formation and stabilization of big radicals (e.g. red ). The products with maintained LOS structure, however, always showed light green or blue coloration (due to and radicals) and bigger radicals never were detected (EPR). It is likely that the sulfur radicals in the products occupy rather eri cages in LOS structure, whereas the large los cages do not accommodate any radicals, because several of them could stay there and subsequently recombine to ordinary oligosulfides. Some reduction of los cage size by means of Cs or K cations resulted in a degradation of LOS structure. Introduction of sulfur compounds already during the losod crystallization disturbed formation of LOS structure. [Copyright &y& Elsevier]

Abstract: The aim of the work was to collect information concerning boundary effects which are suspected in α-alanine dosimeters consisted of powdered microcrystalline α-alanine and binders. In our experiments the conventional binders were replaced by molecular sieves (MS). MS are inorganic porous materials (host structures) with well organized and uniform intra-crystalline pore systems of nano-scale size. The guest molecules can be either physically adsorbed on very large inner MS surface, or chemically bound to the active sites. They can be also encapsulated inside the intracrystalline cavities. The EPR spectra of gamma irradiated dl-α-alanine supported on NaY, CeY, SOD, mordenite, ZSM-5 and ALPO4-5 were very similar to that one observed for irradiated microcrystalline dl-α-alanine. In the case of alanine supported on HY an initial EPR spectrum was different and only after some weeks it made resemble to the well known quintet observed in microcrystalline samples. In sodalites synthesized in the presence of dl-α-alanine EPR signal appeared in non-irradiated sample was very low and structureless. The irradiated sample showed a distinct spectrum which was quite different from that one observed for crystalline dl-α-alanine. [Copyright &y& Elsevier]

Abstract: Colored products have been obtained by thermal treatment of erionite mixed with elemental sulfur and alkalis (Na2CO3 or K2CO3). Synthesis at lower temperature (500°C) resulted in forming colored materials with preserved ERI structure (particularly with potassium cations), whereas the treatment of highly alkaline mixtures at high temperature (800°C) caused re-crystallization to SOD (when Na was used) or to unknown structures (with K). The ESR spectra of the products with preserved original ERI structure recorded at room temperature show two signals, one with g =2.030 and another with g tensor value either 2.045 (for sodium containing samples) or 2.005 (for the potassium bearing products). The latter signal could be considered as a reflection of radicals immobilized in small ε-cages, but it is more likely that it presents anisotropic component of the radical spectrum. The spectra measured at 77K show anisotropy indicating three values of orthorhombic g-tensor, which is typical of radical, although the values vary for particular samples. [Copyright &y& Elsevier]

Abstract: The colored (greenish) products analogous to ultramarine obtained from zeolite A, cancrinite and erionite by means of high-temperature (500–800°C) treatment of zeolites mixed with elemental sulfur and alkalis can maintain the original structure of the parent zeolite under certain preparation conditions. The ESR spectra of samples recorded at room temperature always indicate the presence of radicals S3 − (the blue chromophore). The spectra of samples prepared from zeolites recorded at 77K exhibit additional signals that could be assigned to the yellow chromophore (the radical S2 −) encapsulated inside the β or ε-cages. It is remarkable that in the case of products with preserved cancrinite structure, where the S2 − radicals are encapsulated inside the ε-cages, the above signals are visible already at room temperature. It may result from retarded mobility of these species in small cancrinite cages. [Copyright &y& Elsevier]

The metallosilicalites (MFI) containing copper ([Cu,Si]), zinc ([Zn,Si]) or both elements ([Cu,Zn,Si]) were prepared and modified as potential catalysts for the NO reduction with propene. The H-[Cu,Si] samples showed the highest activity, which was initially comparable to that of Cu-ZSM-5, but contrary to the latter, it increased with time. The framework Cu or Cu released from the framework probably act as active sites. [ABSTRACT FROM AUTHOR]

The metallosilicalites (MFI) containing copper ([Cu,Si]), zinc ([Zn,Si]) or both elements ([Cu,Zn,Si]) were prepared and modified as potential catalysts for the NO reduction with propene. The H-[Cu,Si] samples showed the highest activity, which was initially comparable to that of Cu-ZSM-5, but contrary to the latter, it increased with time. The framework Cu or Cu released from the framework probably act as active sites. [ABSTRACT FROM AUTHOR]

Abstract: The colored products analogous to ultramarine have been obtained by thermal treatment (500–800°C) of cancrinite mixed with elemental sulfur and alkalis. The samples obtained at 500°C maintain the original structure of cancrinite, while heating of the mixture at 800°C resulted in zeolite structure transformation towards SOD in the case of mixture containing Na+ cations and to kaliophilite or unknown structures, when K+ or Li+ were applied as alkali sources. Encapsulation of sulfur species inside the cancrinite cages does not result in the generation of another radicals but , which is reflected in the ESR spectra resembling those embedded in sodalite cages. [Copyright &y& Elsevier]

Imidazole molecules entrapped in porous materials can exhibit high and stable proton conductivity suitable for elevated temperature (>373 K) fuel cell applications. In this study, new anhydrous proton conductors based on imidazole and mesoporous KIT-6 were prepared. To explore the impact of the acidic nature of the porous matrix on proton conduction, a series of KIT-6 materials with varying Si/Al ratios and pure silica materials were synthesized. These materials were additionally modified with cerium atoms to enhance their Brønsted acidity. TPD-NH3 and esterification model reaction confirmed that incorporating aluminum into the silica framework and subsequent modification with cerium atoms generated additional acidic sites. UV-Vis and XPS identified the presence of Ce3+ and Ce4+ in the KIT-6 materials, indicating that high-temperature treatment after cerium introduction may lead to partial cerium incorporation into the framework. EIS studies demonstrated that dispersing imidazole within the KIT-6 matrices resulted in composites showing high proton conductivity over a wide temperature range (300–393 K). The presence of weak acidic centers, particularly Brønsted sites, was found to be beneficial for achieving high conductivity. Cerium-modified composites exhibited conductivity surpassing that of molten imidazole, with the highest conductivity (1.13 × 10−3 S/cm at 393 K) recorded under anhydrous conditions for Ce-KIT-6. Furthermore, all tested composites maintained high stability over multiple heating and cooling cycles. [ABSTRACT FROM AUTHOR]

The present work concerns proton-conducting composites obtained by replacing the water molecules present in aluminophosphate and silicoaluminophosphate AFI-type molecular sieves (AlPO-5 and SAPO-5) with azole molecules (imidazole or 1,2,4-triazole). Both the introduction of azoles and the generation of Brønsted acid centers by isomorphous substitution in aluminophosphate materials were aimed at improving the proton conductivity of the materials and its stability. In the presented study, AlPO-5 and several SAPO-5 materials differing in silicon content were synthesized. The obtained porous matrices were studied using PXRD, low-temperature nitrogen sorption, TPD-NH3, FTIR, and SEM. The proton conductivity of composites was measured using impedance spectroscopy. The results show that the increase in silicon content of the porous matrices is accompanied by an increase in their acidity. However, this does not translate into an increase in the conductivity of the azole composites. Triazole composites show lower conductivity and significantly higher activation energies than imidazole composites; however, most triazole composites show much higher stability. The different conductivity values for imidazole and triazole composites may be due to differences in chemical properties of the azoles. [ABSTRACT FROM AUTHOR]

Abstract: MOF-5 and ZIF-8 were used for the first time as matrices for pigments containing entrapped dmit. The chromophore was introduced either by impregnation or by its synthesis from CS2 inside the matrices. Pigments with ZIF-8 resisted washing and maintained the structure, while these with MOF-5 underwent structure altering or amorphization. [Copyright &y& Elsevier]

Imidazole (Im) introduced into the channels of H-MFI zeolites (with diverse framework Si/Al) shows remarkably enhanced proton conductivity in a broad temperature range (303–393 K), which increased with Im loading. Some conductivity raise is already noticed after its introduction into slilicalite-1 (i.e. SiO 2) due to escalated Im dispersion and subsequently enhanced mobility inside the channels. The increase, however, becomes much more spectacular for the Im composites based on H-forms of aluminosilicate MFI zeolite matrices. It results from additional beneficial interaction of the guest Im with the zeolite acid sites, particularly OH groups, acting as additional proton carriers. Nevertheless, there is no straight correlation between the number of acid sites and the proton conductivity. It seems that the strong Lewis acid sites, contrary to Broensted centers, hinder the conduction, because of firm bonding the Im molecules and reducing their motion. Thus, both kind of sites compete with each other. The highest conduction noticed for the composites based on the H-zeolite with Si/Al = 50 results not so much from pronounced contribution of Broensted centers, but rather from the small number of Lewis sites which are relatively weak. Both Grotthuss and vehicle conductivity modes could be considered. Image 1 • Anhydrous proton conductors. • Imidazole entrapped in H-zeolites MFI with various Si/Al. • Impact of acid sites on composite conductivity. [ABSTRACT FROM AUTHOR]

X-band electron spin resonance (ESR) spectra of S3- radicals in ultramarine analog (pigment) prepared from zeolite A and maintaining the original structure of parent zeolite were recorded in the temperature range of 4.2–380 K. Electron spin echo experiments (echo detected ESR, electron spin-lattice relaxation, and spin echo dephasing) were performed in the temperature range of 4.2–50 K. The rigid lattice g factors are gx=2.0016, gy=2.0505, and gz=2.0355, and they are gradually averaged with temperature to the final collapse into a single line with g=2.028 above 300 K. This is due to reorientations of S3- molecule between 12 possible orientations in the sodalite cage through the energy barrier of 2.4 kJ/mol. The low-lying orbital states of the open form of S3- molecule having C2v symmetry are considered and molecular orbital (MO) theory of the g factors is presented. The orbital mixing coefficients were calculated from experimental g factors and available theoretical orbital splitting. They indicate that the unpaired electron spin density in the ground state is localized mainly (about 50%) on the central sulfur atom of S3- anion radical, whereas in the excited electronic state the density is localized mainly on the lateral sulfur atoms (90%). A strong broadening of the ESR lines in directions around the twofold symmetry axis of the radical S3- molecule (z-axis) is discovered below 10 K. It is due to a distribution of the S–S–S bond angle value influencing mainly the energy of the 2B2-symmetry MO. This effect is smeared out by molecular dynamics at higher temperatures. A distribution of the g factors is confirmed by the recovery of the spin system magnetization during spin-lattice relaxation measurements, which is described by a stretched exponential function. Both the spin-lattice relaxation and electron spin echo dephasing are governed by localized phonon mode of energy of about 40 cm-1. Thus, the anion-radical S3- molecules are weakly bonded to the zeolite framework, and they do not participate in the phonon motion of the host lattice because of their own local dynamics. [ABSTRACT FROM AUTHOR]

Abstract Imidazole entrapped in H-forms of FAU zeolites with various Si/Al ratios (1, 4, 40) exhibit high and stable proton conductivity (up to ∼10−3 S/cm) in a broad range of temperatures (293–393 K). The conductivity increases with temperature and imidazole loading. The number and strength of zeolite acid sites (resulting from various Si/Al) influence markedly the conductivity of composites. The samples based on zeolites with low Si/Al (1) show markedly higher conduction than these supported on the matrix with medium Si/Al (4), regardless of very similar number of the acid OH groups. The strong acid OH groups in zeolite with Si/Al = 4 result in protonation and immobilization of adsorbed imidazole, which reduce their mobility and subsequently the conduction. The low siliceous with weaker acid sites protonate imidazole and form a chain of H-bonds effective in proton propagation. Almost neutral high silica matrix provides a high mobility of dispersed imidazole, due to weak mutual interaction. The overloaded samples indicate a phase transition effect at elevated temperature due to melting of extra-matrix imidazole, which is reflected in dramatic increase in conductivity. Graphical abstract Image 1 Highlights • Proton conductivity of imidazole entrapped in H-forms of faujasites. • Role of imidazole loading, phase transition at high temperature. • Influence of Si/Al on efficiency and mechanism of conduction. [ABSTRACT FROM AUTHOR]

Fluorescein was entrapped inside FAU type zeolite (Y) by generating it from resorcinol and phthalic anhydride. Prior to the formation of fluorescein, zeolite Y was modified with various cations (H, Zn, Ce, Na, K). The modified zeolite acted as catalysts for the fluorescein Friedel–Crafts reaction synthesis, while at the same time it played a role of matrix for the stabilization and homogeneous dispersion of the guest molecules. The nature of the different cations influenced the content of fluorescein generated in the zeolite, and favoured the formation of some dye isomers (i.e. anion, dianion, cation or transition metal complex). The contribution of different fluorescein derivatives in the products was reflected in their absorption and fluorescence properties. The H-, Ce-, and Zn- containing Y zeolites revealed the highest content of fluorescein due to their distinct acid active sites. The composites with H- and ZnY zeolites indicated much higher fluorescence than that of the pristine fluorescein. Moreover, fluorescein in zeolite Y matrices did not show any photobleaching under continuous illumination (λ = 730 nm, in a two-photon experiment for 180 s), which suggests that these materials could be used for biomedical applications. [ABSTRACT FROM AUTHOR]

X-ray, UV−vis, FT-infrared, Raman, continuous wave, and pulsed ESR spectroscopy were applied to characterize pigments prepared at 500 °C under vacuum or in air from mixtures of zeolite A (LTA) with sulfur (40 wt %) and anhydrous sodium sulfide (Na2/S = 0.1−0.4). The samples maintained the LTA structure. Sample color results from an S3−absorption band and the shoulder of a UV band. The fingerprint and asymmetric stretch region of the IR spectra show that the pigments synthesized in air have more disordered structures. The S2−/S3−ratio was estimated from Raman spectra. The ESR spectra of S3−radicals show the existence of several phases visible as five different ESR components. Two components dominate: ideal [Na4S3−]3+clusters and clusters existing in a disordered environment. The samples synthesized in air show a substantial distortion of local structure. Synthesis in vacuum leads to products containing about 20% of the ordered crystalline phase. [ABSTRACT FROM AUTHOR]