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

Dingcai Wu,*,† Fei Xu,† Bin Sun,† Ruowen Fu,† Hongkun He,‡ and Krzysztof Matyjaszewski*,‡ †Materials Science Institute, Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, People's Republic of China ‡Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States

Design and Preparation of Porous Polymers

Covalent organic frameworks (COFs) are a class of crystalline porous organic polymers with permanent porosity and highly ordered structures. Unlike other polymers, a significant feature of COFs is that they are structurally predesignable, synthetically controllable, and functionally manageable. In principle, the topological design diagram offers geometric guidance for the structural tiling of extended porous polygons, and the polycondensation reactions provide synthetic ways to construct the predesigned primary and high-order structures. Progress over the past decade in the chemistry of these two aspects undoubtedly established the base of the COF field. By virtue of the availability of organic units and the diversity of topologies and linkages, COFs have emerged as a new field of organic materials that offer a powerful molecular platform for complex structural design and tailor-made functional development. Here we target a comprehensive review of the COF field, provide a historic overview of the chemistry of the COF field, survey the advances in the topology design and synthetic reactions, illustrate the structural features and diversities, scrutinize the development and potential of various functions through elucidating structure-function correlations based on interactions with photons, electrons, holes, spins, ions, and molecules, discuss the key fundamental and challenging issues that need to be addressed, and predict the future directions from chemistry, physics, and materials perspectives.

Covalent Organic Frameworks: Design, Synthesis, and Functions.

Conjugated microporous polymers (CMPs) are a class of organic porous polymers that combine π-conjugated skeletons with permanent nanopores, in sharp contrast to other porous materials that are not π-conjugated and with conventional conjugated polymers that are nonporous. As an emerging material platform, CMPs offer a high flexibility for the molecular design of conjugated skeletons and nanopores. Various chemical reactions, building blocks and synthetic methods have been developed and a broad variety of CMPs with different structures and specific properties have been synthesized, driving the rapid growth of the field. CMPs are unique in that they allow the complementary utilization of π-conjugated skeletons and nanopores for functional exploration; they have shown great potential for challenging energy and environmental issues, as exemplified by their excellent performance in gas adsorption, heterogeneous catalysis, light emitting, light harvesting and electrical energy storage. This review describes the molecular design principles of CMPs, advancements in synthetic and structural studies and the frontiers of functional exploration and potential applications.

Conjugated microporous polymers: design, synthesis and application

Covalent organic frameworks (COFs) are a class of crystalline porous polymer that allows the atomically precise integration of organic units into extended structures with periodic skeletons and ordered nanopores. One important feature of COFs is that they are designable; that is, the geometry and dimensions of the building blocks can be controlled to direct the topological evolution of structural periodicity. The diversity of building blocks and covalent linkage topology schemes make COFs an emerging materials platform for structural control and functional design. Indeed, COF architectures offer confined molecular spaces for the interplay of photons, excitons, electrons, holes, ions and guest molecules, thereby exhibiting unique properties and functions. In this Review, we summarize the major progress in the field of COFs and recent achievements in developing new design principles and synthetic strategies. We highlight cutting-edge functional designs and identify fundamental issues that need to be addressed in conjunction with future research directions from chemistry, physics and materials perspectives. Covalent organic frameworks are crystalline porous polymers with precisely ordered polygon architectures. In this Review we summarize recent advances in the design principles and synthetic reactions, highlight the current status in structural construction and functionality design, and predict challenging issues and future directions.

Covalent organic frameworks: a materials platform for structural and functional designs

Nanoporous organic polymer networks

Porous, fluorescent, covalent triazine-based frameworks (CTFs) are obtained in an unprecedentedly mild reaction, opening up a scalable pathway for molecular building blocks previously thought incompatible with this chemistry. Choice of monomers and synthetic conditions determines the optical properties and nano-scale ordering of these highly microporous materials with BET surface areas exceeding 1100 m(2) g(-1) and exceptional CO(2) capacities (up to 4.17 mmol g(-1)).

Porous, Fluorescent, Covalent Triazine-Based Frameworks Via Room-Temperature and Microwave-Assisted Synthesis

Anthropogenic carbon dioxide emissions are thought to be one cause of global warming. Current methods for CO2 capture result in large energy penalties. Solid adsorbents are a potential method to capture CO2, but the sorbent-sorbate affinity is critical in determining the energetic viability of such processes. In this study, the adsorption of CO2 in a range of microporous organic polymers was tested. These materials adsorb up to 2.20 mmol/g CO2 at 298 K and 1 bar, and thus performance is compared with related porous solids in the literature. The relationship between CO2 uptake and apparent surface area and pore size is described, and this showed that heats of adsorption were important in the low pressure regime. The chemical tuning of gas-sorbent affinity provides a blueprint for the development of improved materials in this area.

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Microporous organic polymers for carbon dioxide capture

We report here the carbon dioxide sorption properties for a series of conjugated microporous polymer (CMP) networks. These CMP materials incorporate a range of chemical functionalities including carboxylic acids, amines, hydroxyl groups, and methyl groups. The carboxylic acid functionalised network, rather than its amine analogue, shows the highest isosteric heat of sorption for CO2. This supports recent computational predictions for metal–organic frameworks and suggests that acid-functionalised frameworks could outperform more widely studied amine sorbents in CO2 capture and separation application.

/pdf/chemical-tuning-of-co2-sorption-in-robust-nanoporous-organic-1vwdgnuhuk.pdf

Chemical tuning of CO2 sorption in robust nanoporous organic polymers

Microporous polymers are covalently bound, entirely organic materials which possess very high surface areas. These materials have been intensively studied within recent years and various interesting properties and possible applications have been discovered and described. This review article starts with the question, what makes microporous polymers special and are there certain features which differentiate them from other microporous materials? Indeed, there are some special structural and functional features found in microporous polymers which make them really unique and merit further exploration. We focus here on microporous polymers which are solution-processable, can be produced as thin films on electrodes by oxidative polymerizations, are π-conjugated organic semiconductors, or which provide the possibility to introduce and exploit distinct functional groups in an otherwise non-functional highly porous environment. Emerging applications for these microporous polymers which make explicit use of these unique features are further presented.

/pdf/trends-and-challenges-for-microporous-polymers-5we3xklpph.pdf

Robert Dawson

Papers

Nanoporous organic polymer networks

Porous, Fluorescent, Covalent Triazine-Based Frameworks Via Room-Temperature and Microwave-Assisted Synthesis

Microporous organic polymers for carbon dioxide capture

Chemical tuning of CO2 sorption in robust nanoporous organic polymers

Trends and challenges for microporous polymers