Evolution of covalent organic frameworks: from design to real-world applications

Covalent Organic Frameworks are highly versatile porous materials that have attracted much attention over the last few years. This review summarizes the timeline of its development, highlighting the shifts in the targets deemed necessary to use them in real-world applications. We have collected aspects concerning COF formation and the strategies developed to gain chemical stability by using different linkages between the initial building blocks and modulating the structural characteristics of COFs. Importantly, we have also included elements concerning material processability that has been incorporated in the research field of COFs but are essential to solving many different applications of COFs. Finally, we included a summary section providing headlines of this research field to get closer to real applicationsThis work has been supported by the Spanish MICINN (PID2019- 106268GB-C32, and TED2021-129886B-C42) and through the “María de Maeztu” Programme for Units of Excellence in R&D (CEX2018- 000805-M). We also thank financial support to the Comunidad de Madrid (MAD2D-CM) and MICINN (Planes complementarios, Materiales Avanzados

How reproducible are surface areas calculated from the BET equation?

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAMPorosity and surface area analysis play a prominent role in modern materials science. At the heart of this sits the Brunauer–Emmett–Teller (BET) theory, which has been a remarkably successful contribution to the field of materials science. The BET method was developed in the 1930s for open surfaces but is now the most widely used metric for the estimation of surface areas of micro- and mesoporous materials. Despite its widespread use, the calculation of BET surface areas causes a spread in reported areas, resulting in reproducibility problems in both academia and industry. To prove this, for this analysis, 18 already-measured raw adsorption isotherms were provided to sixty-one labs, who were asked to calculate the corresponding BET areas. This round-robin exercise resulted in a wide range of values. Here, the reproducibility of BET area determination from identical isotherms is demonstrated to be a largely ignored issue, raising critical concerns over the reliability of reported BET areas. To solve this major issue, a new computational approach to accurately and systematically determine the BET area of nanoporous materials is developed. The software, called “BET surface identification” (BETSI), expands on the well-known Rouquerol criteria and makes an unambiguous BET area assignment possibl

Electrochemical Double-Layer capacitor based on Carbon@ covalent organic framework aerogels

High energy demand results in comprehensive research of novel materials for energy sources and storage applications. Covalent organic frameworks (COFs) possess appropriate features such as long-range order, permanent porosity, tunable pore size, and ion diffusion pathways to be competitive electrode materials. Herein, we present a deep electrochemical study of two COF-aerogels shaped into flexible COF-electrodes (ECOFs) by a simple compression method to fabricate an electrochemical double-layer capacitor (EDLC). This energy storage system has considerable interest owing to its high-power density and long cycle life compared with batteries. Our result confirmed the outstanding behavior of ECOFs as EDLC devices with a capacity retention of almost 100 % after 10 000 charge/discharge cycles and, to our knowledge, the highest areal capacitance (9.55 mF cm−2) in aqueous electrolytes at higher scan rates (1000 mV s−1) for COFs. More importantly, the hierarchical porosity observed in the ECOFs increases ion transport, which permits a fast interface polarization (low τ0 values). The complete sheds light on using ECOFs as novel electrode material to fabricate EDLC devicesThis work has been supported by the Spanish MINECO (PID2019-106268GB-C32) and through the “María de Maeztu” Programme for Units of Excellence in R&D (CEX2018-000805

Evaluation of the degradation of the graphene-polypropylene composites of masks in harsh working conditions

The recent COVID-19 outbreak has led health authorities to recommend at least the use of surgical masks, most preferably respirators (FFP2 or KN95), to prevent the spread of the virus. Non-woven fabrics have been chosen as the best option to manufacture the face masks, due to their filtration efficiency, low cost, and versatility. Modifying the mask filters with graphene has been of great interest due to its potential use as antibacterial and virucidal properties. Indeed, some companies have commercialized face masks in which graphene is coated and/or embedded. However, the Canadian sanitary authorities advised against using the Shandong Shengquan New Materials Co. graphene masks because of the possibility of pulmonary damage produced by graphene inhalation. Thus, we have analyzed the stability of the graphene filter of these masks and compared it with two other commercially available graphene mask filters, evaluating the morphological and spectroscopical change of the fibers, as well as the particles released during the endurance tests. Our work introduces the necessary tools and methodology to evaluate the potential degradation of face masks under extreme working conditions. These methods complement the present standard tests ensuring the security of the new filters based on composites or nanomaterialsWe thank Ministerio de Ciencia e Innovacion (projects PID2019- 106268GB-C31 and PID2019-106268GB-C32), the financial support through the “María de Maeztu” Programme for Units of Excellence in R&D (CEX2018-000805-M) and Banco de Santander CRUE (Fondo Supera COVID-19

AFM manipulation of gold nanowires to build electrical circuits

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Nano Letters , copyright © American Chemical Society after peer review and technical editing by the publisher. To acces final work see “AFM Manipulation of Gold Nanowires To Build Electrical Circuits”, Nano Letters 19.8 (2019): 5459-5468, https://doi.org/10.1021/acs.nanolett.9b01972We introduce scanning-probe-assisted nanowire circuitry (SPANC) as a new method to fabricate electrodes for the characterization of electrical transport properties at the nanoscale. SPANC uses an atomic force microscope (AFM) to manipulate nanowires to create complex and highly conductive nanostructures (paths) that work as nanoelectrodes, allowing connectivity and electrical characterization of other nano-objects. The paths are formed by the spontaneous cold welding of gold nanowires upon mechanical contact, leading to an excellent contact resistance of ∼9 ω/junction. SPANC is an easy to use and cost-effective technique that fabricates clean nanodevices. Hence, this new method can complement and/or be an alternative to other well-established methods to fabricate nanocircuits such as electron beam lithography (EBL). The circuits made by SPANC are easily reconfigurable, and their fabrication does not require the use of polymers and chemicals. In this work, we present a few examples that illustrate the capabilities of this method, allowing robust device fabrication and electrical characterization of several nano-objects with sizes down to ∼10 nm, well below the current smallest size able to be contacted in a device using the standard available technology (∼30 nm). Importantly, we also provide the first experimental determination of the sheet resistance of thin antimonene flake

A nanostructured Cu(II) coordination polymer based on alanine as a trifunctional mimic enzyme and efficient composite in the detection of Sphingobacteria

This research raises the potential use of coordination polymers as new useful materials in two essential research fields, allowing the obtaining of a new multiartificial enzyme with the capacity to inhibit the growth of bacteria resistance. The fine selection of the ligands allows the design of a new 2D coordination polymer (CP), with the formula [Cu2(IBA)2(OH2)4]n·6nH2O, by the combination of Cu (II) as the metal center with a pseudoamino acid (H2IBA = isophthaloyl bis β-alanine). Quantitative total X-ray fluorescence (TXRF) analyses show that the obtained CP can gradually release Cu (II) ions. Additionally, this CP can be nanoprocessed and transformed into a metal-organic gel (MOG) by using different Cu (II) salt concentrations and the application of ultrasounds. Considering its nanometric dimensions, the slow Cu (II) release and its simple processability, its performance as an artificial enzyme, and its antibacterial ability were explored. The results obtained show the first nanocoordination polymer acting as an artificial multienzyme (peroxidase, catalase, and superoxodismutase) exhibiting antibacterial activity in the presence of hydrogen peroxide, with selective behavior for three bacterium strains (S. spiritovirum, A. faecales, and B. cereus). Indeed, this CP shows a more robust inhibition capacity for Sphingobacterium. Going beyond that, as there are no comfortable and practically clinical tests capable of detecting the presence of Sphingobacteria, the compound can be easily embedded to form moldable gelatin that will facilitate the handling and low-cost commercial kit

Iron Oxyhydroxide-Covalent Organic Framework Nanocomposite for Efficient As(III) Removal in Water

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 conditionsThis 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

Synergistic enhancement of electrochemiluminescence through hybridization of α-Ge nanolayers and gold nanoparticles for highly sensitive detection of tyramine

This work presents a novel approach for detecting biogenic amine tyramine using a sensitive and disposable electrochemiluminescent sensor. The sensor is fabricated by modifying a screen-printed carbon electrode surface with two nanomaterials, α-Ge nanolayers and AuNP, which synergistically enhance the electrochemiluminescence response. The sensor was characterized using various techniques such as SEM-EDX, EIS, Raman, and AFM. The principle of the biosensor relays on the fact that tyramine molecule acts as an analyte and co-reactant, which interacts with the luminophore [Ru(bpy)3] 2+ on the sensor surface. The proposed sensor shows a linear response to tyramine concentration, with a detection limit of 2.28 µM. The sensor successfully detected tyramine in avocado samples, demonstrating its potential for practical applicationsThis work has been supported the Comunidad Autonoma ´ de Madrid (2021-5A/BIO-20943 Talent Attraction Project, SI3/PJI/2021-00341 and S2018/NMT-4349 TRANSNANOAVANSENS-CM Program) and by the Spanish Ministerio de Ciencia e Innovacion ´ (PID2020-116728RBI00, PDC2021-120782-C21, PID2019-106268GB-C32 and TED2021- 129738B-I00). This work has also been supported by the Spanish MINECO (PID2019-106268GB-C32, CEX2018-000805-M and PDC2021- 120782-C21). We acknowledge the support from the “(MAD2D-CM)- UAM” project funded by Comunidad de Madrid, by the Recovery, Transformation and Resilience Plan, and by NextGenerationEU from the European Unio

Evaluation of the oxygen reduction reaction electrocatalytic activity of postsynthetically modified covalent organic frameworks

The pyrolysis of organic precursors to produce heteroatomic-doped carbonaceous materials has emerged as a powerful tool to construct metal-free heterogeneous electrocatalysts due to their low cost and their environmental friendliness. However, the lack of control in the atomic positions or the location of the chemical functionalities makes it difficult to establish structure-property relationships. Herein, we report an easy strategy to compare the electrocatalytic oxygen reduction reaction (ORR) performance of metal-free and nonpyrolyzed materials by postsynthetic modification of covalent organic frameworks (COFs) via click-chemistry. This method facilitates the evaluation of different active centers using materials with the same morphology and prevents active site agglomeration by covalently anchoring these moieties inside of a porous and crystalline framework. In this study we developed a series of diimide-based materials (XDI0.17-COFs) with a loading of 7.65 × 10-4 mol of active site/mg of host COF. The bulk COFs have been delaminated to perform electrode modification by drop-casting. The electrocatalytic response toward the ORR has been studied in alkaline media obtaining the best results for the NDI0.17-COF with an onset potential of 0.77 V (vs reversible hydrogen electrode, RHE) and a limiting current of 4.2 mA/cm2 by a preferred pathway toward water electroreduction. Finally, an adequate combination of density functional theory with the thermochemical Gibbs free energy formalism has been used to theoretically rationalize the ORR mechanism in these metal-free and nonpyrolyzed materials. We have obtained theoretical ORR overpotentials for each COF system agreeing with the experimental observation, which correlate with the ability of the NDI, BzDI, and PDI molecular blocks to accommodate electrons. Our work provides a guideline on how to study the electrocatalytic performance of different organic moieties in metal-free and non-pyrolyzed COFs avoiding their de novo synthesis by using the click postsynthetic methodologyTED2021-129886B-C43, PID2019-106268GB-C32, RED2018-102412-T, PID2020-116728RB-I00, PID2020-113142RB-C21, PLEC2021-007906, 2018/NMT-4349TRANSNANOAVANSENS, S2018/NMT-4367, Y2020/NMT646

3D printing of covalent organic frameworks: a microfluidic-based system to manufacture binder-free macroscopic monoliths

Covalent organic frameworks (COFs) have witnessed outstanding developments in the past 15 years, particularly in optimizing their pore structures, linkages, and variety of monomers used in their synthesis. Yet, a significant challenge remains unaddressed: the processability of COFs into macroscopic architectures with arbitrary shapes, as they are typically obtained as unprocessable powders. This study presents a novel strategy to address this issue by developing a 3D printable ink comprising a colloidal water suspension of COF nanoparticles. A microfluidic device is engineered that provides precise control over the gelation process of the COF-based ink, allowing for a layer-by-layer fabrication. As a result, the direct production of large-scale binder-free COF architectures from digital designs is achieved at room temperature and atmospheric pressure while eliminating the use of toxic organic solventsThis work had been supported by the Spanish MINECO (PID2019- 106268GB-C32, PID2022-138908NB-C31, TED2021-129886B-C42, PDC2022-133498-I00, and PID2020-116612RB-C33). The authors acknowledge the service from the MiNa Laboratory at IMN and funding from CM (project S2018/NMT-4291 TEC2SPACE), MINECO (project CSIC13-4E-1794) and EU (FEDER, FSE). F.Z. acknowledges 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). S.P., J.P.-L., and F. Z. also acknowledge support from the European Innovation Council under grant Agreement 101047081 (EVA). The authors acknowledge the support from the “(MAD2D-CM)-UAM” project funded by Comunidad de Madrid, by the Recovery, Transformation and Resilience Plan, and by NextGenerationEU from the European Unio