Roland A. Fischer

Advances in flexible and functional metal-organic frameworks (MOFs), also called soft porous crystals, are reviewed by covering the literature of the five years period 2009-2013 with reference to the early pertinent work since the late 1990s. Flexible MOFs combine the crystalline order of the underlying coordination network with cooperative structural transformability. These materials can respond to physical and chemical stimuli of various kinds in a tunable fashion by molecular design, which does not exist for other known solid-state materials. Among the fascinating properties are so-called breathing and swelling phenomena as a function of host-guest interactions. Phase transitions are triggered by guest adsorption/desorption, photochemical, thermal, and mechanical stimuli. Other important flexible properties of MOFs, such as linker rotation and sub-net sliding, which are not necessarily accompanied by crystallographic phase transitions, are briefly mentioned as well. Emphasis is given on reviewing the recent progress in application of in situ characterization techniques and the results of theoretical approaches to characterize and understand the breathing mechanisms and phase transitions. The flexible MOF systems, which are discussed, are categorized by the type of metal-nodes involved and how their coordination chemistry with the linker molecules controls the framework dynamics. Aspects of tailoring the flexible and responsive properties by the mixed component solid-solution concept are included, and as well examples of possible applications of flexible metal-organic frameworks for separation, catalysis, sensing, and biomedicine.

The applications and potentials of thin film coatings of metal-organic frameworks (MOFs) supported on various substrates are discussed in this critical review. Because the demand for fabricating such porous coatings is rather obvious, in the past years several synthesis schemes have been developed for the preparation of thin porous MOF films. Interestingly, although this is an emerging field seeing a rapid development a number of different applications on MOF films were either already demonstrated or have been proposed. This review focuses on the fabrication of continuous, thin porous films, either supported on solid substrates or as free-standing membranes. The availability of such two-dimensional types of porous coatings opened the door for a number of new perspectives for functionalizing surfaces. Also for the porous materials themselves, the availability of a solid support to which the MOF-films are rigidly (in a mechanical sense) anchored provides access to applications not available for the typical MOF powders with particle sizes of a few μm. We will also address some of the potential and applications of thin films in different fields like luminescence, QCM-based sensors, optoelectronics, gas separation and catalysis. A separate chapter has been devoted to the delamination of MOF thin films and discusses the potential to use them as free-standing membranes or as nano-containers. The review also demonstrates the possibility of using MOF thin films as model systems for detailed studies on MOF-related phenomena, e.g. adsorption and diffusion of small molecules into MOFs as well as the formation mechanism of MOFs (101 references).

Defect engineering in metal-organic frameworks (MOFs) is an exciting concept for tailoring material properties, which opens up novel opportunities not only in sorption and catalysis, but also in controlling more challenging physical characteristics such as band gap as well as magnetic and electrical/conductive properties. It is challenging to structurally characterize the inherent or intentionally created defects of various types, and there have so far been few efforts to comprehensively discuss these issues. Based on selected reports spanning the last decades, this Review closes that gap by providing both a concise overview of defects in MOFs, or more broadly coordination network compounds (CNCs), including their classification and characterization, together with the (potential) applications of defective CNCs/MOFs. Moreover, we will highlight important aspects of "defect-engineering" concepts applied for CNCs, also in comparison with relevant solid materials such as zeolites or COFs. Finally, we discuss the future potential of defect-engineered CNCs.

ADVERTISEMENT RETURN TO ISSUEPREVReviewNEXTMetal–Organic Framework Thin Films: From Fundamentals to Applications.Angélique Bétard and Roland A. Fischer*View Author Information Anorganische Chemie II, Organometallics and Materials, Ruhr-Universität Bochum, D-44780 Bochum, Germany*E-mail: [email protected]Cite this: Chem. Rev. 2012, 112, 2, 1055–1083Publication Date (Web):September 20, 2011Publication History Received12 May 2011Published online20 September 2011Published inissue 8 February 2012https://pubs.acs.org/doi/10.1021/cr200167vhttps://doi.org/10.1021/cr200167vreview-articleACS PublicationsCopyright © 2011 American Chemical SocietyRequest reuse permissionsArticle Views33536Altmetric-Citations1031LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Crystallization,Crystals,Deposition,Metal organic frameworks,Thin films Get e-Alerts

Efficient reversible oxygen electrodes for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are vitally important for various energy conversion devices, such as regenerative fuel cells and metal-air batteries. However, realization of such electrodes is impeded by insufficient activity and instability of electrocatalysts for both water splitting and oxygen reduction. We report highly active bifunctional electrocatalysts for oxygen electrodes comprising core-shell Co@Co3O4 nanoparticles embedded in CNT-grafted N-doped carbon-polyhedra obtained by the pyrolysis of cobalt metal-organic framework (ZIF-67) in a reductive H2 atmosphere and subsequent controlled oxidative calcination. The catalysts afford 0.85 V reversible overvoltage in 0.1 m KOH, surpassing Pt/C, IrO2 , and RuO2 and thus ranking them among one of the best non-precious-metal electrocatalysts for reversible oxygen electrodes.