Metal–Organic Frameworks – Heading towards Application

Abstract

Guest Editors Pascal Dietzel and Hiroshi Kitagawa give an overview of the papers clustered together in this issue on metal–organic frameworks with emphasis on applications. Over the past two decades, research on metal–organic frameworks, or porous coordination polymers, has become a vast and diverse field within chemistry and materials science. More than twenty years ago, the systematic exploration of using the straightforward principles of coordination chemistry to assemble macroscopic crystalline molecules, which frequently contained large solvent-filled volumes, was eagerly taken up by a growing number of researchers within the chemical community. In these early days, the preparation and structure determination of any new framework material was a testament to the skill of the experimentalist and represented success in itself. Even though, Hoskins and Robson already pointed out in their seminal paper in 1989 that this class of giant framework materials might have potential for useful properties and application in many different areas such as molecular sieves, in ion exchange, and as materials with unusual mechanical and electrical properties and catalysis.1 The potential for application in such a diverse range of areas spawns from the extraordinary variety of inorganic and organic building units that can be used to make MOFs, which essentially leaves it up to the ingenuity of the scientist to choose building units that afford the property he or she wishes to incorporate into the framework material and the complicit participation of nature in that the desired material actually forms under the selected reaction conditions. While the investigation of the properties of MOFs in respect to their behavior within gas adsorption quickly became a focus of many researchers entering the field, not surprising considering the large pore space many of these compounds exhibited, many other areas of application were referred to more in words than in deed in these early days. This has changed in the past decade. More than ever before, all facets of the properties of MOFs are being explored by curious scientists in all their exciting diversity. This thematic issue will present some current progress as metal–organic frameworks head towards application. The issue contains more than thirty Microreviews, Communications and Full Papers. The contributions reflect the large variation of research performed within the field. The issue starts off with an Essay by Gérard Férey. He gives a personal account of the development of the field and the challenges it faces in respect to making the transition to industrial relevance. Gérard replied to our invitation with great enthusiasm and amazing speed. We feel very much indebted to him for this delightful-to-read and inspirational food for thought. At the core of any material that finds its way into application is an efficient pathway for its synthesis. A number of contributions deal with syntheses of new MOFs and advances in controlling the preparation of MOFs. Among these are three Microreviews: H. Reinsch summarizes the "green" synthesis of metal–organic frameworks, F. Costantino et al. give an overview on robust metal–organic frameworks based on tritopic phosphonoaromatic ligands and R. J. Marshall and R. S. Forgan focus on the post-synthetic modification of zirconium MOFs. H.-C. Zhou et al. extend the modulation approach in the synthesis of MOFs to a change in the oxidation state of the metal precursor. J. T. Hupp, O. K. Farha and co-workers transform one MOF into another using a combination of solvent-assisted linker exchange and node transmetallation and report an example of a zirconium MOF with the topology. H. Reinsch, N. Stock, et al. present a scalable "green" synthesis of zirconium MOFs. J. J. Richardson, P. Falcaro and co-workers describe how the growth of metal–organic frameworks can be controlled using gravitational forces. D. Matoga et al. report carboxylate–hydrazone mixed-linker MOFs and their characterization. S. J. Loeb and co-workers present the use of a hexacarboxylate rotaxane linker in the construction of a zinc-based MOF. Adsorption-related applications are still a major field of investigation within MOFs. Despite twenty-something years of studying their sorption properties, there are still phenomena that are not fully understood and new behaviors to be observed. One of these is touched upon in the Microreview by H. Oh and M. Hirscher on the use of MOFs in the separation of hydrogen isotopes by quantum sieving. In a Full Paper, T. K. Woo et al. use a computational approach to screen several hundred thousand MOF structures for viability in CO2 capture. M. Hartmann, F. J. Keil, et al. present a combined experimental and theoretical study on the olefin/paraffin separation potential of selected zeolitic imidazolate frameworks. J. Li et al. present a study on flexible metal–organic frameworks with discriminatory gate-opening effect, which allows for the separation of acetylene from ethylene. MOFs will have to undergo some kind of formulation before becoming available in application-oriented markets. A good understanding of the effects of shaping and mechanical properties of the material is important at this stage. P. L. Llewellyn et al. discuss how shaping affects the gas adsorption properties of selected MOFs. R. Schmid and co-workers perform a multiscale investigation on how mesopores impact the mechanical stability of HKUST-1. P. G. Yot et al. investigate the impact of the metal center and functionalization on the mechanical behavior of MIL-53 MOFs. When they are not used as bulk material to separate mixtures of fluids, membranes are an alternative to employ MOFs with beneficial properties in separation applications. C. Janiak, K. Müller-Buschbaum and co-workers report on the incorporation of luminescent lanthanide MOFs in mixed-matrix membranes. H. B. T. Jeazet, J. Coronas, C. Janiak, et al. also incorporate two MOFs, MIL-101 and ZIF-8, in a mixed-matrix membrane, which leads to increased selectivity in CO2/CH4 separation. Catalysis using MOFs was for many years more alluded to and only rarely tested. This has changed. A. Corma, F. X. Llabrés i Xamena, et al. study the diastereoselective synthesis of pyranoquinolines over UiO-66-type MOFs. C. Wang, W. Lin and co-workers report the use of a rhenium-functionalized MOF as single site catalyst for photochemical reduction of carbon dioxide. S. Ma et al. report on an anionic metal–organic framework that has been used for selective dye removal and catalytic addition of CO2 and epoxides. Recent developments in the area of ferroelectric MOFs are summarized in a Microreview by K. Asadi and M. A. van der Veen. The proton-conducting properties of MOFs are the subject of contributions by R. Vaidhyanathan et al., who report the enhancement of proton conduction by five orders of magnitude by doping a zwitterionic metal–organic framework with cesium ions, and S.-S. Bao, L.-M. Zheng and co-workers, who investigate the effect of counterions on the proton conduction in mixed-metal 2D frameworks. The combination of porosity and guest-sensitive chemical function in the framework, which frequently affects the optical behavior of the material, has direct relevance for the use of MOFs in sensing applications. S. Kaskel et al. investigate the vapochromic luminescence of a zirconium-based MOF, which allows differentiation between non-polar aromatic and non-aromatic compounds and between protic and aprotic polar solvents. H. Wang, B. Chen, et al. explore the selective gas separation and luminescence sensing of different metals using a MOF based on a large organic tetraphenylethene linker. T. J. Sørensen, A. L. Goodwin and co-workers investigate the thermal expansion and thermochromism of silver dicyanamide. MOFs can also be used as porous carrier materials for nanoparticles. P. van der Voort et al. study [email protected] as a selective and regenerable adsorbent for removal of arsenic species from water, while Q. Xu et al. report on the high catalytic performance of NiRu alloy nanoparticles that are immobilized on MIL-101 towards hydrolytic dehydrogenation of ammonia borane. C. Roch-Marchal, P. Horcajada and co-workers show how in situ synthesis of Au nanoparticles with a reduced polyoxometalate in the mesopores of MIL-101 leads to a material that can be used in catalysis and as a theranostic agent. Recently, it has been realized that decomposing MOFs under controlled conditions may be used in a practical approach to obtain nanostructured metal oxides. L. C. Gómez-Aguirre, S. Castro-García, et al. report on the synthesis of hollow microtubes of cobalt oxide made in this way. In addition, we, as guest editors, contribute results from our own research groups on the differences in the structural transformation in two MOFs based on a racemic mixture of a chiral organic linker and the conducting behavior and valence ordering of a one-dimensional coordination polymer under high pressure. It is our pleasure to present this thematic issue "Metal–Organic Frameworks – Heading towards Application", but it would not have come to fruition without the dedication and effort invested by many people, to whom we wish to extend our heartfelt gratitude. In particular, we wish to thank the authors for their high-quality contributions and the editors and editorial office at Wiley-VCH who have organized the compilation of this issue with great dedication and kept it running smoothly throughout the process. It was a privilege to work with everybody involved. Pascal D. C. Dietzel received his diploma degree in chemistry from the University of Bonn. He conducted research for his dissertation at the Max-Planck-Institute for Solid State Research in Stuttgart and received his doctoral degree from the University of Stuttgart (2003). He then joined SINTEF Materials and Chemistry in Oslo (2004–2011) before moving to the University of Bergen in 2011 as Professor for Inorganic Nanochemistry at the Department of Chemistry. His broad research interests include inorganic materials and coordination polymers, crystallography and energy-related applications. Hiroshi Kitagawa received his Ph.D. from Kyoto University in 1992. He moved to the Institute for Molecular Science (IMS) as an assistant professor in 1991, Japan Advanced Institute of Science & Technology (JAIST) as an assistant professor in 1994, University of Tsukuba as an associate professor in 2000, and Kyushu University as a professor in 2003. In 2009, he returned to the original laboratory at Kyoto University. He held a visiting appointment at Davy-Faraday Research Laboratory, Royal Institution of Great Britain (1993–1994). His research fields are solid-state chemistry, coordination chemistry, nanoscience, low-dimensional electron systems, and molecule-based conductors.