Introduction to Reticular Chemistry

Metal-Organic Frameworks and Covalent Organic Frameworks

Omar M. Yaghi, Markus J. Kalmutzki, Christian S. Diercks

• Publisher: Wiley-VCH
• Year: 2019
• ISBN:
  9783527821105
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Inorganic Chemistry

A concise introduction to the chemistry and design principles behind important metal-organic frameworks and related porous materials Reticular chemistry has been applied to synthesize new classes of porous materials that are successfully used for myraid applications in areas such as gas separation, catalysis, energy, and electronics. Introduction to Reticular Chemistry gives an unique overview of the principles of the chemistry behind metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and zeolitic imidazolate frameworks (ZIFs). Written by one of the pioneers in the field, this book covers all important aspects of reticular chemistry, including design and synthesis, properties and characterization, as well as current and future applications Designed to be an accessible resource, the book is written in an easy-to-understand style. It includes an extensive bibliography, and offers figures and videos of crystal structures that are available as an electronic supplement. Introduction to Reticular Chemistry: -Describes the underlying principles and design elements for the synthesis of important metal-organic frameworks (MOFs) and related materials
-Discusses both real-life and future applications in various fields, such as clean energy and water adsorption
-Offers all graphic material on a companion website
-Provides first-hand knowledge by Omar Yaghi, one of the pioneers in the field, and his team. Aimed at graduate students in chemistry, structural chemists, inorganic chemists, organic chemists, catalytic chemists, and others, Introduction to Reticular Chemistry is a groundbreaking book that explores the chemistry principles and applications of MOFs, COFs, and ZIFs.

Part I
Metal-Organic Frameworks

1
Emergence of Metal‐Organic Frameworks

1.1 Introduction

Reticular chemistry¹ is the study of linking discrete chemical entities (molecules and clusters) by strong bonds to make extended structures such as metal‐organic frameworks (MOFs). In MOFs, polynuclear metal clusters are joined together by organic linkers to make crystalline porous frameworks. MOFs combine the synthetic control exercised in making organic molecules with the vast geometric and compositional variations possible by using inorganic units. The reticular chemistry of MOFs has combined two fields of chemistry that have been practiced and taught separately, into one. Accordingly, the synthesis of MOFs requires the well‐honed skills of both organic and inorganic chemists to make extended solids with precisely designed structures and properties. These are imparted by the constituents yet go beyond what would be possible by the individual molecular building units. One such property is the open space encompassed by the framework into which molecules can be introduced and transformed in a manner not possible otherwise. Given the potential of reticular synthesis and the place it is beginning to occupy in the larger context of chemistry, it is instructive to provide a historical perspective on how this new field has emerged. Since MOFs were the first class of crystalline solids to be developed in the realm of reticular chemistry, their history figures prominently in its initial development.

1.2 Early Examples of Coordination Solids

The field of synthetic metal‐organic chemistry as it is practiced today has emerged from coordination chemistry. Early examples of transition metal complexes were discovered by serendipity centuries ago and at that time only little was known about their structure and composition. The first reported example of a synthetic coordination compound can be traced back to the discovery of the pigment “Prussian blue” in Berlin, Germany, in the beginning of the eighteenth century [1]. The story of this finding is captured in a book by Georg E. Stahl [2]. According to him, the discovery of Prussian blue took place in the laboratories of Johann K. Dippel who was preparing a so‐called “animal oil” by distillation of animal materials. This was then repeatedly distilled from potash (K₂CO₃) to remove undesired impurities. This procedure promotes the decomposition of organic components to form cyanide, which subsequently reacts with residual iron from the animal blood to form hexacyanoferrate ions [M₂Fe(CN)₆] (M = Na⁺, K⁺), which stays behind as an impurity in the potash. At that time, a color maker named Johann J. Diesbach worked in Dippel's laboratory synthesizing “Florentine lake,” an organic red pigment based on cochineal red. Usually, he accomplished this by precipitation of an extract of cochineal with potash and the addition of alum [KAl(SO₄)₂·12H₂O] and iron sulfate (FeSO₄) to enhance both the color and the processing of the resulting pigment. At one point, Diesbach had run out of potash so he borrowed some of the potash that had been used in the production of Dippel's animal oil. To his surprise, upon addition of this contaminated potash he observed an unexpected rich blue precipitate, later termed Prussian blue,

[Fe²⁺(CN)₆]₃·H₂O.

Owing to their intense colors, a variety of coordination compounds have had widespread practical use throughout history as pigments (e.g. Prussian blue) and dyes (e.g. alizarin) without knowledge of their chemical composition or structure [1c , 3]. As illustrated with this representative example, the serendipitous discoveries of coordination compounds at that time severely limited the number of accessible materials and hence conclusions about their behavior were exclusively based on phenomenological observations.

1.3 Werner Complexes

The conceptual foundation of coordination chemistry was laid by the Swiss chemist Alfred Werner, who was ultimately awarded the Nobel Prize in chemistry in 1913 for his efforts [4]. When he started his career in 1890 he tried to elucidate and conceptualize the spatial arrangement of atoms in coordination complexes [5]. In 1857, F. August Kekulé proposed the model of constant valence, which was based on the general assumption that every element only exists in one valence and therefore only has one fixed coordination number [6]. Chemical formulae were consequently given using the dot notation, as in CoCl₃·6NH₃, which gave a correct description of the chemical composition but, as Werner later determined, did not represent the actual molecular structure (Figure 1.1).

Figure 1.1 Chemical structure of CoCl₃·6NH₃ based on the theory of constant valence. According to this theory cobalt has a valence of three and therefore has three ligands attached (trigonal arrangement) with the remaining ligands forming chains.

A key observation that led to this conclusion was that addition of hydrochloric acid to a solution of CoCl₃·6NH₃ did not result in the quantitative liberation of all six ammonia molecules per complex. The fact that some ammonia was not released led Werner to deduce that it must be bound tightly to the central cobalt atom. In contrast, upon addition of aqueous silver nitrate, all the chloride ions were precipitated as silver chloride. ...