Please cite this article in press as: G. Varga, et al., Syntheses, characterization and catalytic activities of CaAl-layered double hydroxide intercalated Fe(III)-amino acid complexes, Catal. Today (2016), http://dx.doi.org/10.1016/j.cattod.2016.12.005 ARTICLE IN PRESS G Model CATTOD-10495; No. of Pages 9 Catalysis Today xxx (2016) xxx–xxx Contents lists available at ScienceDirect Catalysis Today journal homepage: www.elsevier.com/locate/cattod Syntheses, characterization and catalytic activities of CaAl-layered double hydroxide intercalated Fe(III)-amino acid complexes Gábor Varga a,b , Zita Timár a,b , Szabolcs Muráth a,b , Zoltán Kónya c,d , Ákos Kukovecz c,e , Stefan Carlson f , Pál Sipos b,g , István Pálinkó a,b,∗ a Department of Organic Chemistry, University of Szeged, Dóm tér 8, Szeged, H-6720 Hungary b Materials and Solution Structure Research Group, Institute of Chemistry, University of Szeged, Aradi Vértanúk tere 1, Szeged, H-6720 Hungary c Department of Applied and Environmental Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged, H-6720 Hungary d MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, Rerrich Béla tér 1, Szeged, H-6720 Hungary e MTA-SZTE “Lendület” Porous Nanocomposites Research Group, Rerrich Béla tér 1, Szeged, H-6720 Hungary f Max-IV Laboratory, Lund University, Lund, Sweden g Department of Inorganic and Analytical Chemistry, University of Szeged, Dóm tér 7, Szeged, H-6720 Hungary a r t i c l e i n f o Article history: Received 26 August 2016 Received in revised form 10 October 2016 Accepted 1 December 2016 Available online xxx Keywords: Structural characterisation Fe(III)-amino acid complexes in CaAl-LDH Catalytic properties Oxidation reactions Ullman-type etherification a b s t r a c t Synthesis of intercalated composites were carried out using CaAl-LDH (layered double hydroxide) as host and the anionic form of Fe(III)-amino acid complexes as guest materials. Intercalation was attempted with two methods either introducing the preformed complexes or constructing the complex among the layers of the LDH. After optimization of the synthesis parameters, structural characterization was performed by X-ray diffractometry, scanning electron microscopy as well as mid and far infrared spectroscopies. Quan- titative data about the intercalated complexes were collected by chemical analysis and X-ray absorption spectroscopy investigating the near edge region as well as the extended fine structure. Structural models based on characterization measurements are also given. Catalytic activities, selectivities and recycling abilities of the substances were studied in the oxidation reactions of cyclohexene with peracetic acid and in situ formed iodosylbenzene as oxidants in the liquid phase. The catalysts were active in the Ullmann- type etherification coupling reaction as well. The intercalated substances were found to be efficient and highly selective catalysts with very good recycling abilities. © 2016 Elsevier B.V. All rights reserved. 1. Introduction Homogeneous catalysts are most often complex compounds containing a metal (ion) and various organic compounds as ligands [1]. They can be highly active and extremely selective. However, their recovery from the reaction mixture and, therefore, their reuse is usually difficult if not impossible. Heterogenisation is a common method of eliminating these drawbacks [2,3], although some activ- ity and selectivity losses may be expected. A chance of minimizing these disadvantageous features may be offered if immobilization occurs by keeping the identity of the complex. Moreover, if immobi- lization is performed in a constrained environment [4], e.g., among the layers of layered double hydroxides (LDHs) [5–7], the shape selective effects of the host material may be exploited. ∗ Corresponding author at: Department of Organic Chemistry, University of Szeged, Dóm tér 8, Szeged, H-6720 Hungary. E-mail address: palinko@chem.u-szeged.hu (I. Pálinkó). Fe(III)-containing amino acid complexes, as the cofactors in var- ious oxidoreductase enzymes are found in nature as the redox centres of these biological catalysts. As redox catalysts, they have important role in laboratory organic transformations as well. In order to facilitate easier recovery and increase durability, these complexes are frequently anchored to various host materials like functionalized silica gel [8] or zeolite [9]. However, to the best of our knowledge such compounds have never been introduced among the layers of LDHs of any type. LDHs, because of the relative ease of their synthesis, represent inexpensive, versatile and potentially recyclable source of catalyst supports [10–12], catalyst precursors [13–15] or actual catalysts [16–19]. LDHs can be found in nature, but for applications they are usually synthesized. They have many representatives, and they have been classified [20]. Part of the hydrotalcite supergroup is the hydrocalumite subgroup − the name giving mineral has the for- mula of [Ca 2 Al(OH) 6 ]A×nH 2 O, where A is a monovalent anion – having corrugated brucite-like main layers, which contain ordered arrangements of Ca 2+ and Al 3+ or other trivalent ions, seven- and http://dx.doi.org/10.1016/j.cattod.2016.12.005 0920-5861/© 2016 Elsevier B.V. All rights reserved.