Crystallizing covalent organic frameworks from metal organic framework through chemical induced-phase engineering.

The ordered porous frameworks like MOFs and COFs are generally constructed using the monomers through distinctive metal-coordinated and covalent linkages. Meanwhile, the inter-structural transition between each class of these porous materials is an under-explored research area. However, such altered frameworks are expected to have exciting features compared to their pristine versions.

Enzyme-immobilized hierarchically porous covalent organic framework biocomposite for catalytic degradation of broad-range emerging pollutants in water.

Efficient enzyme immobilization is crucial for the successful commercialization of large-scale enzymatic water treatment. However, issues such as lack of high enzyme loading coupled with enzyme leaching present challenges for the widespread adoption of immobilized enzyme systems. The present study describes the development and bioremediation application of an enzyme biocomposite employing a cationic macrocycle-based covalent organic framework (COF) with hierarchical porosity for the immobilization of horseradish peroxidase (HRP).

Chemically Gradient Hydrogen-Bonded Organic Framework Crystal Film.

Hydrogen-bonded organic frameworks (HOFs) are ordered supramolecular solid structures, however, nothing much explored as centimetre-scale self-standing films. The fabrication of such crystals comprising self-supported films is challenging due to the limited flexibility and interaction of the crystals, and therefore studies on two-dimensional macrostructures of HOFs are limited to external supports. Herein, we introduce a novel chemical gradient strategy to fabricate a crystal-deposited HOF film on an in situ-formed covalent organic polymer film (Tam-Bdca-CGHOF).

Tuning the electrical properties of graphene oxide through low-temperature thermal annealing.

During the last fifteen years, the reduction of electrically insulating graphene oxide (GO) through the elimination of oxygen containing functional groups and the restoration of sp conjugation yielding its conducting form, known as reduced graphene oxide (rGO), has been widely investigated as a scalable and low-cost method to produce materials featuring graphene-like characteristics. Among various protocols, thermal annealing represents an attractive green approach compatible with industrial processes. However, the high temperatures typically required to accomplish this process are energetically demanding and are incompatible with the use of plastic substrates often desired for flexible electronics applications.

Covalent Organic Framework Based on Azacalix[4]arene for the Efficient Capture of Dialysis Waste Products.

Azacalix[]arenes (ACAs) are lesser-known cousins of calix[]arenes that contain amine bridges instead of methylene bridges, so they generally have higher flexibility due to enlarged cavities. Herein, we report a highly substituted cationic azacalix[4]arene-based covalent organic framework () synthesized by the Zincke reaction under microwave irradiation. The current work is a rare example of a synthetic strategy that utilizes the chemical functionalization of an organic macrocycle to constrain its conformational flexibility and, thereby, produce an ordered material.

Solid-State Photo-NMR Study on Light-Induced Nitrosyl Linkage Isomers Uncovers Their Structural, Electronic, and Diamagnetic Nature.

A light-induced linkage NO isomer (MS1) in -[Ru(NO)(py)F](ClO) is detected and measured for the first time by solid-state MAS NMR. Chemical shift tensors of N and F, along with (N-F) spin-spin couplings and relaxation times of MS1, are compared with the ground state (GS) at temperatures < 250 K. Isotropic chemical shifts (N and F) are well resolved for two crystallographically independent cations (A and B) [Ru(NO)(py)F], allowing to define separately both populations of MS1 isomers and thermal decay rates for two structural sites.

Metallated Isoindigo-Porphyrin Covalent Organic Framework Photocatalyst with a Narrow Band Gap for Efficient CO Conversion.

Photocatalytic CO reduction into formate (HCOO) has been widely studied with semiconductor and molecule-based systems, but it is rarely investigated with covalent organic frameworks (COFs). Herein, we report a novel donor-acceptor COF named composed of isoindigo and metallated porphyrin subunits that exhibits high catalytic efficiency (∼50 μmol formate g h) at low-power visible-light irradiation and in the absence of rare metal cocatalysts. Density functional theory calculations and experimental diffuse-reflectance measurements are used to explain the origin of catalytic efficiency and the particularly low band gap (0.

Infrared spectroscopy quantification of functional carbon groups in kerogens and coals: A calibration procedure.

The determination of the abundances of the CH, C = O and aromatic groups in chondritic Insoluble Organic Matter (IOM) and coals by Infrared (IR) spectroscopy is a challenging issue due to insufficient knowledge on the absorption cross-sections and their sensitivity to the molecular environment. Here, we report a calibration approach based on a C synthetic model material whose composition was unambiguously determined by Direct-Pulse/Magic Angle Spinning Nuclear Magnetic Resonance (DP/MAS NMR). Ratios of the cross-sections of the CH, C = O and aromatic groups have been determined, and the method has been applied to IOM samples extracted from four chondrites as Orgueil (CI), Murchison (CM), Tagish Lake (C2-ungrouped) and EET 92042 (CR2), and to a series of coals.

Rapid and Efficient Removal of Perfluorooctanoic Acid from Water with Fluorine-Rich Calixarene-Based Porous Polymers.

On account of its nonbiodegradable nature and persistence in the environment, perfluorooctanoic acid (PFOA) accumulates in water resources and poses serious environmental issues in many parts of the world. Here, we present the development of two fluorine-rich calix[4]arene-based porous polymers, and , and demonstrate their utility for the efficient removal of PFOA from water. These materials featured Brunauer-Emmett-Teller (BET) surface areas of up to 450 m g, which is slightly lower than their nonfluorinated counterparts (up to 596 m g).

Is carboxylation an efficient method for graphene oxide functionalization?

Graphene oxide (GO) is one of the most popular materials applied in different research areas thanks to its unique properties. The application of GO requires well-designed protocols to introduce different functionalities on its surface, exploiting the oxygenated groups already present. Due to the complex and unstable chemical environment on the GO surface, it is recommended to perform the functionalization under mild conditions.

Synthesis of Robust MOFs@COFs Porous Hybrid Materials via an Aza-Diels-Alder Reaction: Towards High-Performance Supercapacitor Materials.

Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have attracted enormous attention in recent years. Recently, MOF@COF are emerging as hybrid architectures combining the unique features of the individual components to enable the generation of materials displaying novel physicochemical properties. Herein we report an unprecedented use of aza-Diels-Alder cycloaddition reaction as post-synthetic modification of MOF@COF-LZU1, to generate aza-MOFs@COFs hybrid porous materials with extended π-delocalization.

Kinetics of H-C multiple-contact cross-polarization as a powerful tool to determine the structure and dynamics of complex materials: application to graphene oxide.

Hartmann-Hahn cross-polarization (HHCP) is the most widely used solid-state NMR technique to enhance the magnetization of dilute spins from abundant spins. Furthermore, as the kinetics of CP depends on dipolar interactions, it contains valuable information on molecular structure and dynamics. In this work, analytical solutions are derived for the kinetics of HHCP and multiple-contact CP (MC-CP) using both classical and non-classical spin-coupling models including the effects of molecular dynamics and several H, C relaxation and H-C CP experiments are performed in graphene oxide (GO).

Strategies for the Controlled Covalent Double Functionalization of Graphene Oxide.

Graphene oxide (GO) is a versatile platform with unique properties that have found broad applications in the biomedical field. Double functionalization is a key aspect in the design of multifunctional GO with combined imaging, targeting, and therapeutic properties. Compared to noncovalent functionalization, covalent strategies lead to GO conjugates with a higher stability in biological fluids.

Remarkably efficient removal of toxic bromate from drinking water with a porphyrin-viologen covalent organic framework.

The presence of carcinogenic bromate (BrO ) in drinking water became a global concern and efforts towards its removal mainly focused on addressing the source. Herein, we rationally designed a porphyrin-based covalent organic framework () with a cationic surface to provide electrostatic interactions and a porphyrin core to induce hydrogen bonding interactions for the efficient removal of BrO from water. Through H-bonding and electrostatic interactions, exhibited an exceptional bromate removal efficiency (maximum adsorption capacity, : 203.

A Straightforward Approach to Multifunctional Graphene.

Graphene has been covalently functionalized through a one-pot reductive pathway using graphite intercalation compounds (GICs), in particular KC , with three different orthogonally protected derivatives of 4-aminobenzylamine. This novel multifunctional platform exhibits excellent bulk functionalization homogeneity (H ) and degree of addition while preserving the chemical functionalities of the organic addends through different protecting groups, namely: tert-butyloxycarbonyl (Boc), benzyloxycarbonyl (Cbz) and phthalimide (Pht). We have employed (temperature-dependent) statistical Raman spectroscopy (SRS), X-ray photoelectron spectroscopy (XPS), magic angle spinning solid state C NMR (MAS-NMR), and a characterization tool consisting of thermogravimetric analysis coupled with gas chromatography and mass spectrometry (TG-GC-MS) to unambiguously demonstrate the covalent binding and the chemical nature of the different molecular linkers.

Solid-State NMR Approaches to Study Protein Structure and Protein-Lipid Interactions.

Solid-state NMR spectroscopy has been developed for the investigation of membrane-associated polypeptides and remains one of the few techniques to reveal high-resolution structural information in liquid-disordered phospholipid bilayers. In particular, oriented samples have been used to investigate the structure, dynamics and topology of membrane polypeptides. Much of the previous solid-state NMR work has been developed and performed on peptides but the technique is constantly expanding towards larger membrane proteins.

Trichogin GA IV Alignment and Oligomerization in Phospholipid Bilayers.

Trichogin GA IV is a short peptaibol with antimicrobial activity. This uncharged, but amphipathic, sequence is aligned at the membrane interface and undergoes a transition to an aggregated state that inserts more deeply into the membrane, an assembly that predominates at a peptide-to-lipid ratio (P/L) of 1:20. In this work, the natural trichogin sequence was prepared and reconstituted into oriented lipid bilayers.

Thioether-Crown-Rich Calix[4]arene Porous Polymer for Highly Efficient Removal of Mercury from Water.

A rational design of adsorbents with high uptake efficiency and fast kinetics for highly toxic pollutants is a key challenge in environmental remediation. Here, we report the design of a well-defined thioether-crown-rich porous calix[4]arene-based mesoporous polymer S-CX4P and its utility in removal of highly relevant toxic mercury (Hg) from water. The polymer shows an exceptional, record-high uptake efficiency of 1686 mg g and the fastest initial adsorption rate of 278 mg g min.

Calix[4]arene-Based Porous Organic Nanosheets.

Calixarenes are a common motif in supramolecular chemistry but have rarely been incorporated in structurally well-defined covalent 2D materials. Such a task is challenging, especially without a template, because of the nonplanar configuration and conformational flexibility of the calixarene ring. Here, we report the first-of-a-kind solvothermal synthesis of a calix[4]arene-based 2D polymer (CX4-NS) that is porous, covalent, and isolated as few-layer thick (3.

Redox-Responsive Covalent Organic Nanosheets from Viologens and Calix[4]arene for Iodine and Toxic Dye Capture.

Owing to their chemical and thermal stabilities, high uptake capacities, and easy recyclability, covalent organic polymers (COPs) have shown promise as pollutant sponges. Herein, we describe the use of diazo coupling to synthesize two cationic COPs, COP1 and COP2 , that incorporate a viologen-based molecular switch and an organic macrocycle, calix[4]arene. The COPs form nanosheets that have height profiles of 6.

Porous Polycalix[4]arenes for Fast and Efficient Removal of Organic Micropollutants from Water.

Organic micropollutants are hazards to the environment and human health. Conventional technologies are often inefficient at removing them from wastewater. For example, commercial activated carbon (AC) exhibits slow uptake rates, limited capacities, and is costly to regenerate.

Bistable [c2] Daisy Chain Rotaxanes as Reversible Muscle-like Actuators in Mechanically Active Gels.

The implementation of molecular machines in polymer science is of high interest to transfer mechanical motions from nanoscale to macroscale in order to access new kinds of active devices and materials. Toward this objective, thermodynamic and topological aspects need to be explored for reaching efficient systems capable of producing a useful work. In this paper we describe the branched polymerization of pH-sensitive bistable [c2] daisy chain rotaxanes by using copper(I)-catalyzed Huisgen 1,3-dipolar cycloaddition ("click chemistry").