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The dream to prepare well-defined materials drives the methodological evolution for molecular synthesis, structural control and materials manufacturing. Among various methods, chemical approaches to design, synthesize, control and engineer small molecules, polymers and networks offer the fundamental strategies. Merging covalent bonds and non-covalent interactions into one method to establish a complex structural composition for specific functions, mimicking biological systems such as DNA, RNA and proteins, is at the centre of chemistry and materials science. Covalent organic frameworks (COFs) are a class of crystalline porous polymers that enable the integration of organic units into highly ordered structures via polymerization. This polymerization system is unique as it deploys covalent bonds to construct the primary order structures of polymeric backbones via polycondensation and leverages on non-covalent interactions to create the high order structures of polymeric networks via supramolecular polymerization in a one-pot reaction system. This Primer covers all aspects of the field of COFs from chemistry to physics, materials and applications, and outlines the design principle, experimental methods, characterization and applications, with an aim to show a concise yet full picture of the field. The key fundamental issues to be addressed are analysed with an outlook on the future major directions from different perspectives.

The presence of heavy metal ions in water is an environmental issue derived mainly from industrial and mineral contamination. Metal ions such as Cd(II), Pb(II), Hg(II), or As(III) are a significant health concern worldwide because of their high toxicity, mobility, and persistence. Covalent organic frameworks (COFs) are an emerging class of crystalline organic porous materials that exhibit very interesting properties such as chemical stability, tailored design, and low density. COFs also allow the formation of composites with remarkable features because of the synergistic combination effect of their components. These characteristics make them suitable for various applications, among which water remediation is highly relevant. Herein, we present a novel nanocomposite of iron oxyhydroxide@COF (FeOOH@Tz-COF) in which lepidocrocite (γ-FeOOH) nanorods are embedded in between the COF nanoparticles favoring As(III) remediation in water. The results show a remarkable 98.4% As(III) uptake capacity in a few minutes and impressive removal efficiency in a wide pH range (pH 5−11). The chemical stability of the material in the working pH range and the capability of capturing other toxic heavy metals such as Pb(II) and Hg(II) without interference confirm the potential of FeOOH@Tz-COF as an effective adsorbent for water remediation even under harsh conditions, This work has been supported by the Spanish MINECO (PID2019-106268GB-C32 and PCI2019-103594) and through the “María de Maeztu” Programme for Units of Excellence in R&D (CEX2018-000805-M)

The use of covalent organic frameworks (COFs) in practical applications demands shaping them into macroscopic objects, which remains challenging. Herein, we report a simple three-step method to produce COF aerogels, based on sol-gel transition, solvent-exchange, and supercritical CO drying, in which 2D imine-based COF sheets link together to form hierarchical porous structures. The resultant COF aerogel monoliths have extremely low densities (ca. 0.02 g cm), high porosity (total porosity values of ca. 99 %), and mechanically behave as elastic materials under a moderate strain (, This work has been supported by the Spanish MINECO (PID2019-106268GB-C32, MAT2016-77608-C3-1-P, PCI2018-093081, PID2019-108028GB-C21, and RTI2018-095622-B-I00), the Catalan AGAUR (project 2017 SGR 238), Basque Government (IT1291-19), and through the “María de Maeztu” Programme for Units of Excellence in R&D (CEX2018-000805-M). It was also funded by the CERCA Program/Generalitat de Catalunya. ICN2 is supported by the Severo Ochoa program from the Spanish MINECO (Grant No. SEV-2017-0706).

Control over the functionalization of graphenic materials is key to enable their full application in electronic and optical technologies. Covalent functionalization strategies have been proposed as an approach to tailor the interfaces’ structure and properties. However, to date, none of the proposed methods allow for a covalent functionalization with control over the grafting density, layer thickness and/or morphology, which are key aspects for fine-tuning the processability and performance of graphenic materials. Here, we show that the no-slip boundary condition at the walls of a continuous flow microfluidic device offers a way to generate controlled chemical gradients onto a graphenic material with 2D and 3D control, a possibility that will allow the sophisticated functionalization of these technologically-relevant materials., Nature Communications, 13 (1), ISSN:2041-1723

2D materials have opened a new field in materials science with outstanding scientific and technological impact. A largely explored route for the preparation of 2D materials is the exfoliation of layered crystals with weak forces between their layers. However, its application to covalent crystals remains elusive. Herein, a further step is taken by introducing the exfoliation of germanium, a narrow-bandgap semiconductor presenting a 3D diamond-like structure with strong covalent bonds. Pure α-germanium is exfoliated following a simple one-step procedure assisted by wet ball-milling, allowing gram-scale fabrication of high-quality layers with large lateral dimensions and nanometer thicknesses. The generated flakes are thoroughly characterized by different techniques, giving evidence that the new 2D material exhibits bandgaps that depend on both the crystallographic direction and the number of layers. Besides potential technological applications, this work is also of interest for the search of 2D materials with new properties, The authors acknowledge the financial support from the Spanish Ministry of Science and Innovation, through the “María de Maeztu” Programme for Units of Excellence in R&D (CEX2018-000805-M and CEX2019-000919-M) and MINECO-FEDER projects PID2019-111742GB-C31, PID2019-111742GB-C32, PCI2018-093081, PID2019-109539GB-C43, MAT2015-666888-C3-3R, MICINN projects FIS2017-82415-R, RTI2018- 097895-B-C43 and PID2019-111742GA-I00, the Comunidad Autónoma de Madrid through S2018/NMT-4321 (NanomagCOST-CM), the Generalitat Valenciana (CIDEGENT/2018/001 grant and iDiFEDER/2018/061 co-financed by FEDER) and the Deutsche Forschungsgemeinschaft (DFG, FLAG-ERA AB694/2-1), the European Union Seventh Framework Programme under Grant agreement No. 604391 Graphene Flagship. The authors thank the European Research Council (ERC Starting Grant 2D-PnictoChem 804110 to G.A.). W.S.P. acknowledges the computer resources and assistance provided by the Centro de Computación Científica of the Universidad Autónoma de Madrid and the computer resources at MareNostrum and technical support provided by Barcelona Supercomputing Center (FI-2019-2-0007)

Covalent organic frameworks (COFs) are crystalline and porous materials with bi- or three-dimensional structures built up by connecting their molecular precursors by dynamic covalent bonds. Using bottom-up or top-down strategies, bi-dimensional COFs can be obtained as single- or few-layer materials, thus enlarging the family of 2D-materials based on graphene. The main advantage of 2D-materials based on COFs is the fact that they can be chemically designed, thus allowing the formation of a la carte materials with well-designed functionalities including their size and features of their pores. The aim of this perspective review is to illustrate in a rational way the current state-of-the-art in the field of COF nanosheet formation using the two general approaches of material nano-structuring. This article reviews a selected collection of samples that illustrates the essential concepts, strategies of preparation following the two general approaches, bottom-up and top-down, and a selection of COF nanolayers showing seminal properties and potential material applications. Finally, we provide some perspectives of this novel research field.

This is the peer reviewed version of the following article: Rodríguez‐San‐Miguel, D., Yazdi, A., Guillerm, V., Pérez‐Carvajal, J., Puntes, V., Maspoch, D., & Zamora, F. (2017). Confining Functional Nanoparticles into Colloidal Imine‐Based COF Spheres by a Sequential Encapsulation–Crystallization Method. Chemistry–A European Journal, 23(36), 8623-8627, which has been published in final form at https://doi.org/10.1002/chem.201702072. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions, Here, a two-step method is reported that enables imparting new functionalities to covalent organic frameworks (COFs) by nanoparticle confinement. The direct reaction between 1,3,5-tris(4-aminophenyl)benzene and 1,3,5-benzenetricarbaldehyde in the presence of a variety of metallic/metal-oxide nanoparticles resulted in embedding of the nanoparticles in amorphous and non-porous imine-linked polymer organic spheres (NP@a-1). Post-treatment reactions of NP@a-1 with acetic acid under reflux led to crystalline and porous imine-based COF-hybrid spheres (NP@c-1). Interestingly, Au@c-1 and Pd@c-1 were found to be catalytically active, This work was supported by the Spanish MINECO (projects PN MAT2016‐77608‐C3‐1‐P and MAT2015‐65354‐C2‐1‐R), the Catalan AGAUR (project 2014 SGR 80), and the ERC under the EU FP7 (ERC‐Co 615954). V.G. is grateful to the Generalitat de Catalunya for a Beatriu de Pinós fellowship (2014 BP‐B 00155). A.Y. and ICN2 acknowledge the support of the Spanish MINECO through the Severo Ochoa Centers of Excellence Program, under Grant SEV‐2013‐0295

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of the American Chemical Society, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/jacs.9b12389, Covalent organic frameworks (COFs) are commonly synthesized under harsh conditions yielding unprocessable powders. Control in their crystallization process and growth has been limited to studies conducted in hazardous organic solvents. Herein, we report a one-pot synthetic method that yields stable aqueous colloidal solutions of sub-20 nm crystalline imine-based COF particles at room temperature and ambient pressure. Additionally, through the combination of experimental and computational studies, we investigated the mechanisms and forces underlying the formation of such imine-based COF colloids in water. Further, we show that our method can be used to process the colloidal solution into 2D and 3D COF shapes as well as to generate a COF ink that can be directly printed onto surfaces. These findings should open new vistas in COF chemistry, enabling new application areas, This work was supported by the European Union (ERC-2015-STG microCrysFact 677020), the Swiss National Science Foundation (Project No. 200021_181988), ETH Zürich and Ministry of Science, Innovation and Universities MICINN (MAT2016-77608-C3-1P). R.P. acknowledges the Spanish MINECO (Grant No. CTQ2017—88948-P). A.E.P.P. acknowledges a TALENTO grant (2017-T1/IND5148) from Comunidad de Madrid. I.S. acknowledges the Ministry of Human Capacities of Hungary (20391-/2018/FEKUSTRAT). G.M.P. acknowledges the funding received by the Swiss National Science Foundation (SNSF grant number 200021_175735) and by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement No. 818776 - DYNAPOL). D.M. acknowledges financial support from the European Union (ERC-Co 615954). ICN2 is supported by the Severo Ochoa program from the Spanish MINECO (Grant No. SEV-2017-0706). S.P. acknowledges funding from a Consolidator Grant from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant Agreement No. 771565). We acknowledge DESY (Hamburg, Germany), a member of the Helmholtz Association HGF, for the provision of experimental facilities. Synchrotron X-ray diffraction experiments with COF-TAPB-BTCA were carried out at the beamline P02.1 PETRA III under the proposal I-20170717 EC. We acknowledge Jaume Caelles for SAXS/WAXS measurements performed at IQAC–CSIC.

Covalent organic frameworks (COFs) are an emerging class of new organic polymers showing tuneable permanent porosity and crystallinity. They are formed, using modular chemistry concepts, by condensation reactions between their molecular precursors based on the formation of dynamic bonds. Despite much effort having been devoted towards the design of the physical and/or chemical properties of these materials by selecting their initial building blocks, the importance of processability for their applications has only recently emerged. This tutorial review article rationalizes the strategies used so far on COF processability leading to the formation of thin-films, membranes, or individual particles with controlled shape and size as well as composite fabrication. We aim to provide a rational perspective of the importance of COF processability towards potential applications of COFs in many different fields which are at the forefront of research in materials science, This work was supported in part by MICINN (grant MAT2016-77608-C3-1-P)

To date, crystallization studies conducted in space laboratories, which are prohibitively costly and unsuitable to most research laboratories, have shown the valuable effects of microgravity during crystal growth and morphogenesis. Herein, an easy and highly efficient method is shown to achieve space-like experimentation conditions on Earth employing custom-made microfluidic devices to fabricate 2D porous crystalline molecular frameworks. It is confirmed that experimentation under these simulated microgravity conditions has unprecedented effects on the orientation, compactness and crack-free generation of 2D porous crystalline molecular frameworks as well as in their integration and crystal morphogenesis. It is believed that this work will provide a new "playground" to chemists, physicists, and materials scientists that desire to process unprecedented 2D functional materials and devices., Advanced Materials, 33 (30), ISSN:0935-9648, ISSN:1521-4095

Can controlled diffusion of reagents together with micro‐shielding features enable the regioselective localization of different chemical processes? In article number 1903172, Josep Puigmarti‐Luis and co‐workers present a method for the in‐situ fabrication of custom designed surface‐enhanced Raman spectroscopy (SERS) substrates as well as for the selective localization of multiple chemical reactions onto surfaces. [Image: see text]

A microfluidic chip has been used to prepare fibres of a porous polymer with high structural order, setting a precedent for the generation of a wide variety of materials using this reagent mixing approach that provides unique materials not accessible easily through bulk processes. The reaction between 1,3,5-tris(4-aminophenyl)benzene and 1,3,5-benzenetricarbaldehyde in acetic acid under continuous microfluidic flow conditions leads to the formation of a highly crystalline and porous covalent organic framework (hereafter denoted as MF-COF-1), consisting of fibrillar micro-structures, which have mechanical stability that allows for direct drawing of objects on a surface, Financial support from Spanish Government (Projects MAT2013-46753-C2-1-P and CTQ2014-53486-R) and FEDER are acknowledged. A. A. and J. P. L. would like to thank the financial support from the Swiss National Science Foundation (SNSF) through the project no. 200021_160174

Covalent Organic Frameworks (COFs) are a class of porous covalent materials which are frequently synthesized as unprocessable crystalline powders. The first COF was reported in 2005 with much effort centered on the establishment of new synthetic routes for its preparation. To date, most available synthetic methods for COF synthesis are based on bulk mixing under solvothermal conditions. Therefore, there is increasing interest in developing systematic protocols for COF synthesis that provide for fine control over reaction conditions and improve COF processability on surfaces, which is essential for their use in practical applications. Herein, we present a novel microfluidic-based method for COF synthesis where the reaction between two constituent building blocks, 1,3,5-benzenetricarbaldehyde (BTCA) and 1,3,5-tris(4-aminophenyl)benzene (TAPB), takes place under controlled diffusion conditions and at room temperature. Using such an approach yields sponge-like, crystalline fibers of a COF material, hereafter called MF-COF. The mechanical properties of MF-COF and the dynamic nature of the approach allow the continuous production of MF-COF fibers and their direct printing onto surfaces. The general method opens new potential applications requiring advanced printing of 2D or 3D COF structures on flexible or rigid surfaces.

Here we report a method that combines the spray-drying technique with a dynamic covalent chemistry process to synthesize zero-dimensional, spherical and microscale superstructures made from the assembly of imine-based COF nanocrystals. This methodology also enables the integration of other functional materials into these superstructures forming COF-based composites., This work was supported by the Spanish MINECO (project PN MAT2015-65354-C2-1-R), the Catalan AGAUR (project 2014 SGR 80), and the ERC under the EU FP7 (ERC-Co 615954). It was also funded by the CERCA Programme/Generalitat de Catalunya. ICN2 acknowledges the support of the Spanish MINECO through the Severo Ochoa Centers of Excellence Program under Grant SEV-2013-0295

The one-pot room-temperature condensation reaction between 1,3,5-tris(4-aminophenyl)benzene and 1,3,5-benzenetricarboxaldehyde in acetone leads to the fast formation of a homogeneous dispersion of well-defined spherical particles of an imine-based covalent organic framework (sRT-COF-1). Supramolecular functionalization of sRT-COF-1 with a variety of surfactants significantly increases the water dispersibility of sRT-COF-1.

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of the American Chemical Society, © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://pubs.acs.org/doi/abs/10.1021/jacs.7b05182, We present the novel potential application of imine-based covalent organic frameworks (COFs), formed by the direct Schiff reaction between 1,3,5-tris(4-aminophenyl)benzene and 1,3,5-benzenetricarbaldehyde building blocks in m-cresol or acetic acid, named RT-COF-1 or RT-COF-1Ac/RT-COF-1AcB. The post-synthetic treatment of RT-COF-1 with LiCl leads to the formation of LiCl@RT-COF-1. The ionic conductivity of this series of polyimine COFs has been characterized at variable temperature and humidity, using electrochemical impedance spectroscopy. LiCl@RT-COF-1 exhibits a conductivity value of 6.45 × 10-3 S cm-1 (at 313 K and 100% relative humidity) which is among the highest values so far reported in proton conduction for COFs. The mechanism of conduction has been determined using 1H and 7Li solid-state nuclear magnetic resonance spectroscopy. Interestingly, these materials, in the presence of controlled amounts of acetic acid and under pressure, show a remarkable processability that gives rise to quasi-transparent and flexible films showing in-plane structural order as confirmed by X-ray crystallography. Finally, we prove that these films are useful for the construction of proton exchange membrane fuel cells (PEMFC) reaching values up to 12.95 mW cm-2 and 53.1 mA cm-2 for maximum power and current density at 323 K, respectively, We thank the MINECO (Spain) for financial support through Juan de la Cierva postdoctoral fellowship. We thank the Spanish Ministry of Economy (MAT2016-77608-C3-1-P, MAT2013-46753-C2-1-P, CTQ2014-53486-R, ENE2016-77055-C3-1-R), and Comunidad de Madrid (S2013/MAE2882) for generous funding

Covalent Organic Frameworks (COFs) based on polyimine with several metal ions (FeIII, CoII and NiII) adsorbed into their cavities have shown the ability to generate N-doped porous graphene from their pyrolysis under controlled conditions. These highly corrugated and porous graphene sheets exhibit high values of specific capacitance, which make them useful as electrode materials for supercapacitors.

This is the peer reviewed version of the following article: Advanced Materials 28.30 (2016): 6332-6336, which has been published in final form at http://dx.doi.org/10.1002/adma.201602128. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving, Antimonene fabricated by mechanical exfoliation is highly stable under atmospheric conditions over periods of months and even when immersed in water. Density functional theory confirms the experiments and predicts an electronic gap of ≈1 eV. These results highlight the use of antimonene for optoelectronics applications, This work was supported by MINECO projects Consolider CSD2010-00024, MAT2013- 46753-C2-1 and 2, FIS2013-42002-R and CTQ2013-43698-P, CAM project NANOFRONTMAG-CM (ref. S2013/MIT-2850)

On page 6332, J. Gomez-Herrero, F. Zamora, and co-workers describe the isolation of antimonene, a new allotrope of antimony that consists of a single layer of atoms. They obtain antimonene flakes by the scotch tape method; these flakes are highly stable in ambient conditions and even when immersed in water. The 1.2 eV gap calculated in this study suggests potential applications in optoelectronics.

2D-polymers are still dominated by graphene and closely related materials such as boron nitride, transition metal sulphides and oxides. However, the rational combination of molecules with suitable design is already showing the high potential of chemistry in this new research field. The aim of this feature article is to illustrate, and provide some perspectives, the current state-of-the-art in the field of synthetic 2D-polymers showing different alternatives to prepare this novel type of polymers based on the rational use of chemistry. This review comprises a brief revision of the essential concepts, the strategies of preparation following the two general approaches, bottom-up and top-down, and a revision of the promising seminal properties showed by some of these nanomaterials.

2D-polymers are still dominated by graphene and closely related materials such as boron nitride, transition metal sulphides and oxides. However, the rational combination of molecules with suitable design is already showing the high potential of chemistry in this new research field. The aim of this feature article is to illustrate, and provide some perspectives, the current state-of-the-art in the field of synthetic 2D-polymers showing different alternatives to prepare this novel type of polymers based on the rational use of chemistry. This review comprises a brief revision of the essential concepts, the strategies of preparation following the two general approaches, bottom-up and top-down, and a revision of the promising seminal properties showed by some of these nanomaterials., Financial support from Spanish MINECO (MAT2013-46753-C2-1-P and MAT2013-46502-C2-2-P). D. R. thanks the Spanish MECD for a FPU grant

We report herein an efficient, fast, and simple synthesis of an imine-based covalent organic framework (COF) at room temperature (hereafter, RT-COF-1). RT-COF-1 shows a layered hexagonal structure exhibiting channels, is robust, and is porous to N2 and CO2. The roomtemperature synthesis has enabled us to fabricate and position low-cost micro- and submicropatterns of RT-COF-1 on several surfaces, including solid SiO2 substrates and flexible acetate paper, by using lithographically controlled wetting and conventional ink-jet printing., We thank the MINECO (Spain) for financial support through projects MAT2013-46753-C2-1-P, MAT2012-30994, and MAT2014-52305-P). A.P. acknowledges UCM for a predoctoral fellowship.

International Edition: DOI: 10.1002/anie.201605298 German Edition: DOI: 10.1002/ange.201605298, "This is the peer reviewed version of the following article: Angewandte Chemie - International Edition 55.46 (2016): 14345-14349 which has been published in final form at https://doi.org/10.1002/anie.201605298. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions", We report on a fast and simple method to produce highly stable isopropanol/water (4:1) suspensions of few-layer antimonene by liquid-phase exfoliation of antimony crystals in a process that is assisted by sonication but does not require the addition of any surfactant. This straightforward method generates dispersions of few-layer antimonene suitable for on-surface isolation. Analysis by atomic force microscopy, scanning transmission electron microscopy, and electron energy loss spectroscopy confirmed the formation of high-quality few-layer antimonene nanosheets with large lateral dimensions. These nanolayers are extremely stable under ambient conditions. Their Raman signals are strongly thickness-dependent, which was rationalized by means of density functional theory calculations