Basolites: a type of Metal Organic Frameworks highly efficient in the one-pot synthesis of quinoxalines from a-hydroxy ketones under aerobic conditions.

We report here efficient synthesis of quinoxalines from ophenylendiamine and -hydroxy ketones over commercial Basolites. The concentration and type of acid centres, as CUS sites, together with the porosity of the samples strongly influence the resulting conversion and selectivity. Our results indicate a new reaction route in which tautomerization reactions are also involved.pre-print624 K

Controlling crystal morphology of anisotropic zeolites with elemental composition

O.V. acknowledges the support of Charles University through the project “Grant Schemes at CU” (Reg. no. CZ.02.2.69/0.0/0.0/19_073/0016935). J.Č. acknowledges the support of the Czech Science Foundation through the project ExPro (19-27551X). W.J.R. acknowledges the financial support from the National Science Centre Poland, grant number 2020/37/B/ST5/01258. M.S. acknowledges the support of the Ministry of Education, Youth and Sports of the Czech Republic through ERC_CZ project LL 2104. This work was also supported by Ministerstvo Školství, Mládeže a Tělovýchovy as ERDF/ESF project TECHSCALE (Nos. CZ.02.01.01/00/22_008/0004587). R.E.M. acknowledges the European Research Council for funding through the AdG 787073 “ADOR” programme.The morphology of zeolite crystals strongly affects their textural, catalytic, and mechanical attributes. However, controlling zeolite crystal morphology without using modifiers or structure-directing agents remains a challenging task because of our limited understanding of the relationships between zeolite crystal shape, crystallization mechanism, and composition of the starting synthesis mixture. In this study, we aimed at developing a general method for controlling the morphology of zeolites by assessing the impact of the Si/T molar ratio of the synthesis gel on the growth rate of zeolite crystals in various crystallographic directions and on the final crystal morphology of the UTL germanosilicate with a 2D system of intersecting 14- and 12-ring pores. Our results showed that flat UTL crystals progressively thicken with the Si/Ge molar ratio, demonstrating that Ge concentration controls the relative rate of crystal growth in the perpendicular direction to the pore system. The morphology of other zeolites and zeotypes with an anisotropic structure, including AFI (12R), IFR (12R), MWW (10–10R), and IWW (12–10–8R), can also be predicted based on their Si/T ratio, suggesting a systematic pattern across zeolite structures and in a wide range of zeolite framework elements. Combined, these findings introduce a facile and cost-efficient method for directly controlling crystal morphology of zeolites with anisotropic structures with a high potential for scale-up while providing further insights into the role of elemental composition in zeolite crystal growth.Peer reviewe

Post-synthesis incorporation of Al into germanosilicate ITH zeolites: the influence of treatment conditions on the acidic properties and catalytic behavior in tetrahydropyranylation

Post-synthesis alumination of germanosilicate medium-pore ITH zeolites was shown to be an effective procedure for tuning their acidity. Treatment of ITH zeolites synthesized with different chemical compositions (i.e. Si/Ge = 2.5, 4.4 and 5.8) with aqueous Al(NO3)(3) solution led to the formation of strong Bronsted and Lewis acid sites and an increasing fraction of ultramicro- and meso-pores in Ge-rich ITH samples (Si/Ge = 2.5 and 4.4). The concentration of Al incorporated into the framework increases with decreasing Si/Ge ratio of the parent ITH. The increasing temperature of alumination from 80 to 175 degrees C (HT conditions) resulted in (1) a 1.5-2-fold increase in the concentration of Bronsted acid sites formed and (2) a decreasing fraction of framework Al atoms detectable with base probe molecules (i.e. pyridine, 2,6-di-tert-butylpyridine), i.e. an increased concentration of the "inner" acid sites. The activity of prepared Al-substituted ITH zeolites in tetrahydropyranylation of alcohols is enhanced with increasing amount of accessible acid sites in bulky crystals (e.g. alumination at lower temperature) or with increasing total concentration of acid centres within tiny ITH crystals (e.g. alumination under HT conditions). This trend became more prominent with increasing kinetic diameter of the substrate molecules under investigation (methanol < 1-propanol < 1-hexanol).Post-synthesis alumination of germanosilicate medium-pore ITH zeolites was shown to be an effective procedure for tuning their acidity. Treatment of ITH zeolites synthesized with different chemical compositions (i.e.Si/Ge = 2.5, 4.4 and 5.8) with aqueous5529732984Czech Science Foundation [14-30898P, 13-17593P

Vapour-phase-transport rearrangement technique for the synthesis of new zeolites

M.S., M.M., R.E.M., J.Č. and M.O. acknowledge OP VVV “Excellent Research Teams” project No.CZ.02.1.01/0.0/0.0/15_003/0000417– CUCAM. M.S. and M.O. thank the Primus Research Program of the Charles University (project number PRIMUS/17/SCI/22 “Soluble zeolites”). R.E.M. also thanks the ERC (Advanced Grant 787073 “ADOR”). A.M. acknowledges The Centre for High-resolution Electron Microscopy (CħEM), supported by SPST of ShanghaiTech University under contract No. EM02161943, and the Natural National Science Foundation of China, through projects NFSC-21850410448 and NSFC- 21835002. Z.L. acknowledges the support from the National Key Research and Development Program of China (2016YFA0300102) and the National Natural Science Foundation of China (11675179, 11434009). J.Č. acknowledges the support of the Czech Science Foundation to the project EXPRO (19-27551×).Owing to the significant difference in the numbers of simulated and experimentally feasible zeolite structures, several alternative strategies have been developed for zeolite synthesis. Despite their rationality and originality, most of these techniques are based on trial-and-error, which makes it difficult to predict the structure of new materials. Assembly-Disassembly-Organization-Reassembly (ADOR) method overcoming this limitation was successfully applied to a limited number of structures with relatively stable crystalline layers ( UTL , UOV , *CTH ). Here, we report a straightforward, vapour-phase-transport strategy for the transformation of IWW zeolite with low-density silica layers connected by labile Ge-rich units into material with new topology. In situ XRD and XANES studies on the mechanism of IWW rearrangement reveal an unusual structural distortion-reconstruction of the framework throughout the process. Therefore, our findings provide a step forward towards engineering nanoporous materials and increasing the number of zeolites available for future applications.Publisher PDFPeer reviewe

Annulation of phenols with methylbutenol over MOFs: The role of catalyst structure and acid strength in producing 2,2-dimethylbenzopyran derivatives

The catalytic behavior of metal-organic frameworks of different structures (Fe(BTC), MIL-100(Fe), MIL-100(Cr) and Cu-3(BTC)(2)) was investigated in annulation reaction between 2-methyl-3-buten-2-ol and phenols differing in size (phenol, 2-naphthol). MIL-100(Fe) possessing intermediate Lewis acidity, perfect crystalline structure, and the highest S-BET surface area showed the highest activity (TOF = 0.7 and 1.4h(-1) for phenol and 2-naphthol, respectively) and selectivities to target benzopyran (45% and 65% at 16% of phenol and 2-naphthol conversion, respectively). The increasing strength of Lewis acid centers for MIL-100(Cr) was found to result in the dramatically decreased activity of the catalyst, while negligible conversion of phenols was found over Fe(BTC), characterized by a less ordered framework.M.O. and J.C. acknowledge the Czech Science Foundation for the support (14-07101S) and RNDr. Libor Brabec, CSc. for SEM images.Shamzhy, MV.; Opanasenko, MV.; García Gómez, H.; Cejka, J. (2015). Annulation of phenols with methylbutenol over MOFs: The role of catalyst structure and acid strength in producing 2,2-dimethylbenzopyran derivatives. Microporous and Mesoporous Materials. 202:297-302. doi:10.1016/j.micromeso.2014.10.003S29730220

Tuning Of Acidic And Catalytic Properties Of Iwr Zeolite By Post-synthesis Incorporation Of Three-valent Elements

Post-synthesis alumination and galliation of borogermanosilicate IWR zeolite in acidic medium (pH 0.5-2.0) was shown to be an efficient approach for tuning its acidic and catalytic properties. The concentration of Al(NO3)(3), pH, and the temperature of the treatment of IWR zeolite were varied and related to the structural and acidic properties of the obtained materials. The concentration of Al incorporated in the framework of IWR increased with increasing concentration of applied Al(NO3)3 solution (in the range 0.1-1.0 M), pH (0.5-2.0), or the temperature (25-95 degrees C) of the treatment. Obtained Ga- and Al-containing IWR zeolites are characterized by a higher concentration of strong Bronsted acid sites (117 and 82-277 mu mol/g vs. 24 mu mol/g) and superior catalytic performance in benzoylation of p-xylene in comparison with parent B-IWR zeolite. The balanced strength of acid centers in Ga-IWR enabling sufficient activation of benzoyl chloride as well as efficient desorption of formed ketone results in the highest yield of target product over Ga-IWR among isomorphously substituted IWR zeolites: B-IWR (5%) < Al-IWR (33%) < Ga-IWR (99%). (C) 2014 Elsevier B.V. All rights reserved.243768