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Błękit Majów , jedno z najważniejszych osiągnięć Mezoameryki

Łukarska M., Zywert A., Kowalak S.

Wiadomości Chemiczne

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2012

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[Z] 66, 7-8

715-739

EN

The Maya Blue is a famous blue pigment developed by pre-Columbian civilizations of Mesoamerica and manufactured there for about thousand years. It was applied for body decoration, important for cruel religious rituals, as well as for artistic paintings, murals, or coloration of ceramics. Its production was abandoned in XVII century and the procedure forgotten. The chemical nature of this blue pigment remained a puzzle for a long time and only in nineteen sixties it was revealed [1, 2] that it is a composite consisting of inorganic matrix (palygorskite) that accommodates molecules of organic dye – indigo. The preparation procedure was rediscovered [3] and the products analogous to classical Maya Blue could be obtained by simple thermal insertion of indigo into palygorskite (and also into sepiolite). However, the nature of chemical interaction between dye and matrix that provides very high resistibility of resulting pigments remains still not satisfactorily explained. The hydrogen bonds or coordinative interaction with matrix cations are taken into an account. Zeolites and other molecular sieves can be efficiently applied as matrices for pigments similar to Maya Blue. The coloration and other properties of pigments can be considerably changed by initial modification of zeolites with various cations, what supports an important role of complexes formed by dye molecules and zeolite cations. On the other hand, the zeolite-like materials AlPO4 as well as to some extent mesoporous silica (with some contribution of micropores) lacking any cations are also efficient matrices for pigments analogous to Maya Blue. Not only indigo, but also indigo derivatives (leucoindigo, thioindigo, indigo carmine) could be embedded inside the molecular sieves. The thermal insertion as well as crystallization of zeolites from gels supplemented with respective dye can be used for pigment synthesis. It is interesting that role of matrix can be also played by representative of novel MOF family of the molecular sieves.

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Materiały MOF, nowa rodzina sit molekularnych o niezwykłych właściwościach i możliwościach zastosowań

Florczak P., Janiszewska E., Kędzierska K., Kowalak S.

Wiadomości Chemiczne

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2011

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[Z] 65, 5-6

427-460

EN

The metal organic frameworks (MOFs) are a novel group of molecular sieves discovered in the last decade of the twentieth century. Most of conventional molecular sieves such as microporous zeolites and zeolite-like materials, ordered mesoporous materials (M41S) are typical inorganic compounds. Although their synthesis often involves an assistance of organic compounds acting as structure directing agents and organic solvents are sometimes applied during their crystallization, the organics are always removed from resulted products (mainly by calcinations). The MOFs are crystalline materials build of metal ions or ion clusters coordinatively bonded with organic segments (linkers) that form porous (one-, two-, or threedimensional) structures. The various coordination number of selected metal and the nature of organic linkers allow to prepare a great variety of structures with different properties. The inorganic components comprise a great variety of transition (e.g. Zn Cu, Fe, rare earths) and base metal (e.g. Al) cations of different valence. The organic linkers are functionalized compounds containing O, N, P, S atoms (i.e. carboxylates, phosphonates, sulfonates, cyanides, amines, imidazoles) enable to chelate the inorganic cations. The organic subunits can be additionally modified by substitution of other functional groups (halogens, hydroxyls, aminogroups). The MOF materials are mostly prepared similarly as zeolitic materials by crystallization in solvothermal conditions. The solvents (water or organic compounds) can play a role of templates, although sometimes additional structure directing agents are admitted into the initial mixtures. The crystallization is always conducted in moderate temperatures (20–200°C). After removal of solvents well ordered pore systems are available for selective adsorption and for other applications. The thermal stability of this family of molecular sieves is obviously lower than that of inorganic materials, but most of them can withstand heating at 350–400°C, which still makes them suitable for variety of potential applications. The adsorption properties of MOFs makes them very appealing for practical application. The recorded surface areas of some types are overwhelming and they surpass 5000 m2/g. The high adsorption capacity is very promising for storage of fuels (natural gas, hydrogen) or waste gases (CO2, SO2) as well as for their separation. The great and very fast growing variety of structures and chemical compositions brings also a hope to use them as efficient catalysts. The metal segments, functional groups in organic blocks as well as occluded or encapsulated species can play a role of catalytically active sites. The MOF materials can be also applied as matrices for sensors, pigments, and microelectronic or optical devices.

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Nowe metody syntezy pigmentów ultramarynowych z użyciem zeolitów

Jankowska A., Kowalak S.

Wiadomości Chemiczne

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2008

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[Z] 62, 7-8

659-682

EN

The natural ultramarine (lazurite, lapis lazuli) has been known and valued since the ancient times as semiprecious gem applied for jewelry, artistic works, decoration and painting. In Middle Ages it was used as excellent, but very expensive pigment. At the beginning of the nineteenth century a method of synthesis of artificial ultramarine has been discovered and it soon became a common inexpensive commercial product applied mostly for production of paints and as an optical brightener. The procedure included heating of the substrate mixtures (kaolin, sulfur, sodium carbonate, reducing agent) in kilns at high temperature (800°C). The technology of ultramarine production has not been substantially changed up to now, whereas the law regulations concerning environment protection imposed in the twentieth century could not accept a serious air pollution (SO2, H2S) always accompanying the production process. Therefore, searching for novel, environmentally friendly procedures becomes challenging. Ultramarine is an aluminosilicate with sodalite structure that contains sulfur anion-radicals (mostly •S3-) combined with Na+ cations embedded inside ?-cages. The sulfur radicals play a role of chromophores (•S3- blue, •S3- yellow). Sodalite is a zeolite and the sodalite units (?-cages) are constituents of structure of several zeolites (LTA, FAU, LTN, EMT). The use of zeolitic structures for encapsulation of sulfur anion radicals appeared very promising. The direct introduction of sulfur radicals from aprotic solutions of oligosulfides [27] was not successful but the thermal treatment of zeolites mixed with sulfur radical precursors (NaSn, S + alkalis) resulted in colored products analogous to ultramarine [24-26, 30, 31]. Zeolites A seem the most useful for preparation of sulfur pigments but other zeolites can be applied as well. The products of various colors (yellow, green blue and sometimes pinky) and shades can be obtained by choosing appropriate zeolite, radi-cal precursor, kind and content of alkaline cation in the initial mixture, temperature (400-800°C) and time of treatment. It was found that zeolite structure can be maintained upon the thermal treatment or it can be transformed (mostly towards SOD) under highly alkaline thermal treatment. The sulfur radicals can also be embedded inside smaller than ?-cages (e.g. CAN) which favors a generation of smaller radicals (i.e. •S2-) [39-42]. It is also possible to incorporate the sulfur compounds into zeolites during their crystallization and then a generation of radical upon heating. The sulfur pigments based on non aluminosilicate matrices (e.g. AlPO4-20) can be also obtained [38, 53]. Generally use of zeolites allows to obtain ultramarine-like pigments with broad range of colors under much milder than conventional conditions and with much lower emission of polluting agents.

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Application of the Molecular Sieves as Matrices for Chromophores Embedded in Their Cages

Kowalak S., Jankowska A.

Polish Journal of Chemistry

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2008

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Vol. 82, nr 1-2

131-140

EN

Zeolite matrices have been applied for embedment of sulfur radical chromophores inside the intra-crystalline cages. The thermal treatment of zeolites (200–800 graduate C) with sulfur radical precursors (oligosulfides, elemental sulfur and alkalis) led to colored products. Their coloration (yellow, green, blue) and structure depended on structure type of parent zeolite (LTA, FAU, SOD, ERI, CAN, GIS, STI, CHA, HEU), alkalinity of the initial mixture, temperature and time of thermal treatment. Synthesis at high temperatures under high alkalinity of mixtures always resulted in recrystallization of parent zeolites towards sodalite, whereas the mild preparation conditions did not affect the original structures of zeolites. Employing of zeolites as starting materials allows to extend the palette of achievable colors of ultramarine pigments.

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Mezoporowate sita molekularne : otrzymywanie i właściwości

Kowalak S., Stawiński K.

Wiadomości Chemiczne

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2000

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[Z] 54, 9-10

817-843

EN

The crystalline molecular sieves comprised almost exclusively microporous materials (zeolites and zeolite-like materials). The pore diameter of this materials was mostly in the range 0,3-0,8 nm. Despite a very narrow range of this diameter, which limits the number of molecules to be applied, the crystalline molecular sieves have attained a great commercial importance for many industrial processes (selective adsorption, ion-exchange, catalysis). The attention of many research groups was focused on syntheses of larger pore structures accessible for bulkier molecules. It was not sure, however, whether such structures could be achieved and if so, whether they would be satisfactory stable to be applied for practical purposes. The successful syntheses of crystalline structures of VPI-5, JDF-20, Cloverite, and UTD-1 indicated that extra-large diameters above 1 nm could be obtained. The structures, on the other hand, appeared not very stable and not easy to be synthesized and modified. Therefore, they have not been commercially applied. The important milestone in modem history of the molecular sieves was discovery of novel family of mesoporous, well organized materials in early ninetieths. This new family of the molecular sieves have been presented independently by Mobil and Toyota at the 9th International Zeolite Conference in Montreal. The first examples of the materials consisted exclusively of silica. Soon later the aluminosilicate mesoporous molecular sieves have been presented and then many other chemical compositions have been employed for synthesis of mesoporous molecular sieves. The materials of this kind are generally called M41S. The principle of synthesis of these materials shows some similarity with the preparation of zeolites and zeolite-like materials in respect to employing of the organic compounds as structure directing agents. The role of a template agent plays usually surfactants such as long alkyl chain amines, which form micelles in a solution. The micelle aggregates are then surrounded by inorganic precursors and the well organized array of voids (e.g. tubes) filled with surfactant molecules are formed due to condensation of an inorganic phase. The organic compounds are removed from the pores mostly by means of thermal treatment. A variety of surfactants applied allows to prepare various structures of different pore sizes (2-10 nm). The growing family of mesoporous molecular sieves contains many unique structures. The most common are: the hexagonal unit cell MCM-41, cubic MCM-48, lamellar structure MCM-50, although the number of defined structures is to date many times higher. Contrary to zeolites and other microporous molecular sieves the M41S are not crystalline materials. The XRD indicates usually only one or few reflections at very low range of 2-theta angle. The mesoporous molecular sieves show very high surface areas (usually above 1000 m2/g) and their adsorption/desorption isotherms of type IV often indicate a hysteresis loop. The transmission electron micrographs indicate a pore array in the lattice image. It has been hoped that the novel materials would show a similar catalytic activity as zeolites. These expectations have not been proven satisfactory so far. The catalytic activity of aluminosilicate mesoporous materials resembles rather activity of the amorphous aluminosilicates. The always growing variety of mesoporous structures and of their chemical compositions provides a chance of finding the materials of high and stable catalytic activity. The pore system of this materials is widely studied as a support accommodating the introduced catalytically active compounds. The mesoporous molecular sieves can be used for many other applications such as adsorption (storage of gases), matrices for microelectronic and optical devices, active fillers for polymers etc.