oa EDITORIAL [Hot Topic :Advanced Characterization of Porous Materials (Guest Editors: Konstantin Hadjiivanov and Georgi N. Vayssilov)]

This special issue aims at presenting some new achievements in the detailed and advanced characterization of micro and mesoporous materials. We realize that the topic is too large to give a complete picture of the state-of-the art. However, we hope that we succeeded to include interesting contributions that can intrigue the reader. We have tried to present the applications of modern techniques to this specific type of modern materials with various complex properties. In the first paper, Colella describes the fascinating history of the birth and the development of the crystalline and ordered porous materials, starting from zeolite discovery, roughly two and half centuries ago, via the appearance of the synthetic zeolites and alternative ordered microporous and mesoporous structures, until the recently created microporous hybrid inorganic-organic frameworks. After this personal overview, there are two papers dealing with IR characterization of porous materials. In the paper of Busca, the use of the technique for obtaining information on the location of surface OH groups is presented. Briefly, combining probe molecules with different size (and therefore different abilities to penetrate in channels and pores) the author demonstrates how location of different hydroxyls can be determined. Note that the approach can be enlarged to (i) other porous materials and (ii) determination of the location of guest cations. The second IR paper (Hadjiivanov et al.) deals with the use of isotopically labeled molecular probes for advanced characterization. In particular the usefulness of the technique to characterize OH groups (and the extent of H-bonding) is shown as well as the power of CO isotopic mixtures for determination of the coordination state of incorporated cations. Another important and presently hot class of porous materials is that of metal-organic frameworks (MOF). They are promising materials for hydrogen storage and this is described in the first paper dealing with MOFs. Spassov et al. summarize the current achievements in room temperature hydrogen storage in various types of MOFs, compares them with alternative materials and the general requirements for the practical applications, and discuss the restrictions and possible ways for improvement of MOFs for hydrogen storage. A constructive and comprehensive overview of the specific features and key results in the utilization of IR spectroscopy in characterization of various types of MOF materials is presented in the paper of Daturi. This contribution provides excellent examples for practical use of IR spectroscopic techniques in clarification structural problems and chemical behavior of such systems. The theoretical modeling has become an integral part of the modern chemistry and the vatious types of micro and mesoporous materials are not an exception in this trend. The different approaches for simulation of the structure, spectral features and properties of such materials are summarized in the review of Vayssilov et al. The authors focus in particular on the achievements of the computational modeling related to transition metal cations and their complexes with small molecules in zeolites and in MOFs. Finally, the last two contributions show interesting application of microporous materials. Kowalak et al. describe the utilization of zeolites and other microporous materials as hosts for pigments taking the advantage from the mechanical and chemical stability of the zeolite framework and its optical transparency. The paper highlights different possibilities for directing and fine tuning of the color of the material by modification of the type and chemical composition of the chromophore, and the treatment of the samples. The classical and one of the most important areas for practical application of zeolites, as heterogeneous catalysts, is demonstrated in the paper of Mota et al. As a case study, they investigated the role of in catalytic transformations of glycerol on protonic forms of zeolites into ethers, acetals/ketals, esters and other dehydration products. The study is related to the search of efficient industrial utilization of glycerol produced as a side product in biodisel production from oils. The Editors would like to use the opportunity to thank all invited contributors for their understanding and dedicated work and the Editor of Current Physical Chemistry for providing the possibility this issue to appear. The topic is hot and large, so likely we will try to go on with a second thematic issue.