Covalent organic frameworks (COFs) represent an exciting new type of porous organic materials, which are ingeniously constructed with organic building units via strong covalent bonds. The well-defined crystalline porous structures together with tailored functionalities have offered the COF materials superior potential in diverse applications, such as gas storage, adsorption, optoelectricity, and catalysis. Since the seminal work of Yaghi and co-workers in 2005, the rapid development in this research area has attracted intensive interest from researchers with diverse expertise. This critical review describes the state-of-the-art development in the design, synthesis, characterisation, and application of the crystalline porous COF materials. Our own opinions on further development of the COF materials are also presented for discussion (155 references).

Covalent organic frameworks (COFs): from design to applications

Metal–organic frameworks (MOFs) or porous coordination polymers (PCPs) are open, crystalline supramolecular coordination architectures with porous facets. These chemically tailorable framework materials are the subject of intense and expansive research, and are particularly relevant in the fields of sensory materials and device engineering. As the subfield of MOF-based sensing has developed, many diverse chemical functionalities have been carefully and rationally implanted into the coordination nanospace of MOF materials. MOFs with widely varied fluorometric sensing properties have been developed using the design principles of crystal engineering and structure–property correlations, resulting in a large and rapidly growing body of literature. This work has led to advancements in a number of crucial sensing domains, including biomolecules, environmental toxins, explosives, ionic species, and many others. Furthermore, new classes of MOF sensory materials utilizing advanced signal transduction by devices based on MOF photonic crystals and thin films have been developed. This comprehensive review summarizes the topical developments in the field of luminescent MOF and MOF-based photonic crystals/thin film sensory materials.

Metal-organic frameworks: functional luminescent and photonic materials for sensing applications.

Covalent organic frameworks (COFs) are a class of crystalline porous polymers that allow the atomically precise integration of organic units to create predesigned skeletons and nanopores. They have recently emerged as a new molecular platform for designing promising organic materials for gas storage, catalysis, and optoelectronic applications. The reversibility of dynamic covalent reactions, diversity of building blocks, and geometry retention are three key factors involved in the reticular design and synthesis of COFs. This tutorial review describes the basic design concepts, the recent synthetic advancements and structural studies, and the frontiers of functional exploration.

Covalent organic frameworks

Conversion of carbon dioxide (CO2) to carbon monoxide (CO) and other value-added carbon products is an important challenge for clean energy research. Here we report modular optimization of covalent organic frameworks (COFs), in which the building units are cobalt porphyrin catalysts linked by organic struts through imine bonds, to prepare a catalytic material for aqueous electrochemical reduction of CO2 to CO. The catalysts exhibit high Faradaic efficiency (90%) and turnover numbers (up to 290,000, with initial turnover frequency of 9400 hour(-1)) at pH 7 with an overpotential of -0.55 volts, equivalent to a 26-fold improvement in activity compared with the molecular cobalt complex, with no degradation over 24 hours. X-ray absorption data reveal the influence of the COF environment on the electronic structure of the catalytic cobalt centers.

/pdf/covalent-organic-frameworks-comprising-cobalt-porphyrins-for-16e0bybrm3.pdf

Covalent organic frameworks comprising cobalt porphyrins for catalytic CO2 reduction in water

Just over a century ago, Lewis published his seminal work on what became known as the covalent bond, which has since occupied a central role in the theory of making organic molecules. With the advent of covalent organic frameworks (COFs), the chemistry of the covalent bond was extended to two- and three-dimensional frameworks. Here, organic molecules are linked by covalent bonds to yield crystalline, porous COFs from light elements (boron, carbon, nitrogen, oxygen, and silicon) that are characterized by high architectural and chemical robustness. This discovery paved the way for carrying out chemistry on frameworks without losing their porosity or crystallinity, and in turn achieving designed properties in materials. The recent union of the covalent and the mechanical bond in the COF provides the opportunity for making woven structures that incorporate flexibility and dynamics into frameworks.

http://science.sciencemag.org/content/sci/355/6328/eaal1585.full.pdf

The atom, the molecule, and the covalent organic framework

Two types (imine and boronate) of covalent organic frameworks (COFs) having a porphyrin unit have been synthesized. The two highly crystalline porphyrin COFs (COF-366 and COF-66) display excellent chemical and thermal stability and are permanently porous. Two-dimensional extended layered structures of the two COFs demonstrate very high charge carrier mobility values (8.1 cm2 V−1 s−1).

/pdf/covalent-organic-frameworks-with-high-charge-carrier-48ueuq9ijb.pdf

Covalent Organic Frameworks with High Charge Carrier Mobility

Mohamad Hmadeh,†,‡ Zheng Lu,†,‡ Zheng Liu, Felipe Gandara,†,‡ Hiroyasu Furukawa,†,‡ Shun Wan,†,‡ Veronica Augustyn, Rui Chang, Lei Liao,‡ Fei Zhou, Emilie Perre, Vidvuds Ozolins, Kazu Suenaga, Xiangfeng Duan,‡ Bruce Dunn, Yasuaki Yamamto, Osamu Terasaki, and Omar M. Yaghi*,†,‡,#,¶ †Center for Reticular Chemistry, Center for Global Mentoring, ‡Department of Chemistry and Biochemistry, and Department of Materials Science and Engineering, University of California, Los Angeles, California 90095, United States Nanotube Research Center, AIST, Tsukuba 305-8565, Japan SMBU, JEOL Ltd., Akishima, Tokyo 196-8558, Japan Department of Materials and Environmental Chemistry and EXSELENT, Stockholm University, Stockholm, Sweden Graduate School of EEWS (WCU), Korea

/pdf/new-porous-crystals-of-extended-metal-catecholates-50n26vxzg0.pdf

New Porous Crystals of Extended Metal-Catecholates

The disclosure relates generally to materials that comprise conductive covalent organic frameworks. The disclosure also relates to materials that are useful to store and separate gas molecules and sensors.

Conductive open frameworks.

The disclosure provides for metal catecholate frameworks, and methods of use thereof, including gas separation, gas storage, catalysis, tunable conductors, supercapacitors, and sensors.

Shun Wan

Papers

Covalent Organic Frameworks with High Charge Carrier Mobility

New Porous Crystals of Extended Metal-Catecholates

Conductive open frameworks.

Preparation of metal-catecholate frameworks

Herstellung von metall-catecholat-rahmen