Graphene / Single-Walled Carbon Nanotube Composites Generated by Covalent Cross-Linking

Tuning of Microenvironment in Covalent Organic Framework via Fluorination Strategy promotes Selective CO2 Capture

Herein, we have designed and synthesized two heteroatom (N, O) rich covalent organic frameworks (COF), PD-COF and TF-COF, respectively, to demonstrate their relative effect on CO₂ adsorption capacity and also CO₂ /N₂ selectivity. Compared to the non-fluorinated PD-COF (BET surface area 805 m²  g^-1 , total pore volume 0.3647 ccg^-1 ), a decrease in BET surface area and also pore volume have been observed for fluorinated TF-COF due to the incorporation of fluorine to the porous framework (BET surface area 451 m²  g^-1 , total pore volume 0.2978 ccg^-1 ). This fact leads to an enormous decrease in the CO₂ adsorption capacity and CO₂ /N₂ selectivity of TF-COF, though it shows stronger affinity towards CO₂ with a Qst of 37.76 KJ/mol. The more CO₂ adsorption capacity by PD-COF can be attributed to the large specific surface area with considerable amount of micropore volume compared to the TF-COF. Further, PD-COF exhibited CO₂ /N₂ selectivity of 16.8, higher than that of TF-COF (CO₂ /N₂ selectivity 13.4).

Introducing Polar Groups in Porous Aromatic Framework for Achieving High Capacity of Organic Molecules and Enhanced Self-Cleaning Applications

Due to the frequent oil/organic solvent leakage, efficient oil/water separation has attracted extensive concern. However, conventional porous materials possess nonpolar building units, which reveal relatively weak affinity for polar organic molecules. Here, two different polarities of superhydrophobic porous aromatic frameworks (PAFs) were synthesized with respective orthoposition and paraposition C=O groups in the PAF linkers. The conjugated structure formed by a large number of alkynyl and benzene ring structures enabled porous and superhydrophobic quality of PAFs. After the successful preparation of the PAF solids, PAF powders were coated on polyester fabrics by a simple dip-coating method, which endowed the resulting polyester fabrics with superhydrophobicity, porosity, and excellent stability. Based on the unique structure, the oil/water separation efficiency of two superhydrophobic flexible fabrics was more than 90% for various organic solvents. Polar LNU-26 PAF showed better separation performance for the polar oils. This work takes the lead in adopting the polar groups as building units for the preparation of porous networks, which has great guiding significance for the construction of advanced oil/water separation materials.

A review on carbon fiber-reinforced hierarchical composites: mechanical performance, manufacturing process, structural applications and allied challenges

The utilization of carbonaceous reinforcement-based polymer matrix composites in structural applications has become a hot topic in composite research. Although conventional carbon fiber-reinforced polymer composites (CFRPs) have revolutionized the composite industry by offering unparalleled features, they are often plagued with a weak interface and lack of toughness. However, the promising aspects of carbon fiber-based fiber hybrid composites and hierarchical composites can compensate for these setbacks. This review provides a meticulous landscape and recent progress of polymer matrix-based different carbonaceous (carbon fiber, carbon nanotube, graphene, and nanodiamond) fillers reinforced composites’ mechanical properties. First, the mechanical performance of neat CFRP was exhaustively analyzed, attributing parameters were listed down, and CFRPs’ mechanical performance barriers were clearly outlined. Here, short carbon fiber-reinforced thermoplastic composite was distinguished as a prospective material. Second, the strategic advantages of fiber hybrid composites over conventional CFRP were elucidated. Third, the mechanical performance of hierarchical composites based on carbon nanotube (1D), graphene (2D) and nanodiamond (0D) was expounded and evaluated against neat CFRP. Fourth, the review comprehensively discussed different fabrication methods, categorized them according to performance and suggested potential future directions. From here, the review sorted out three-dimensional printing (3DP) as the most futuristic fabrication method and thoroughly delivered its pros and cons in the context of the aforementioned carbonaceous materials. To conclude, the structural applications, current challenges and future prospects pertinent to these carbonaceous fillers reinforced composite materials were elaborated.

Chemical Route to Twisted Graphene, Graphene Oxide and Boron Nitride

The recently discovered twisted graphene has attracted considerable interest. A simple chemical route was found to prepare twisted graphene by covalently linking layers of exfoliated graphene containing surface carboxyl groups with an amine-containing linker (trans-1,4-diaminocyclohexane). The twisted graphene shows the expected selected area electron diffraction pattern with sets of diffraction spots out with different angular spacings, unlike graphene, which shows a hexagonal pattern. Twisted multilayer graphene oxide could be prepared by the above procedure. Twisted boron nitride, prepared by cross-linking layers of boron nitride (BN) containing surface amino groups with oxalic acid linker, exhibited a diffraction pattern comparable to that of twisted graphene. First-principles DFT calculations threw light on the structures and the nature of interactions associated with twisted graphene/BN obtained by covalent linking of layers.

Synthesis, characterization, surface properties and energy device characterstics of 2D borocarbonitrides, (BN)xC1−x, covalently cross-linked with sheets of other 2D materials

Covalent cross-linking of 2D structures such as graphene, MoS₂ and C₃N₄ using coupling reactions affords the generation of novel materials with new or improved properties. These covalently cross-linked structures provide the counter point to the van der Waals heterostructures, with an entirely different set of features and potential applications. In this article, we describe the materials obtained by bonding borocarbonitride (BCN) layers with BCN layers as well as with other layered structures such as MoS₂ and C₃N₄. While cross-linking BCN layers with other 2D sheets, we have exploited the existence of different surface functional groups on the graphene (COOH) and BN(NH₂) domains of the borocarbonitrides as quantitatively determined by FLOSS. Hence, we have thus obtained two different BCN–BCN assemblies differing in the location of the cross-linking and these are designated as GG/BCN–BCN and GBN/BCN–BCN, depending on which domains of the BCN are involved in cross-linking. In this study, we have determined the surface areas and CO₂ and H₂ adsorption properties of the cross-linked structures of two borocarbonitride compositions, (BN)_0.75C_0.25 and (BN)_0.3C_0.7. We have also studied their supercapacitor characteristics and photochemical catalytic activity for hydrogen generation. The study reveals that the covalently cross-linked BCN–BCN and BCN–MoS₂ assemblies exhibit increased surface areas and superior supercapacitor performance. The BCN composite with MoS₂ also shows high photochemical HER activity besides electrochemical HER activity comparable to Pt. This observation is significant since MoS₂ in the nanocomposite is in the 2H form. The present study demonstrates the novelty of this new class of materials generated by cross-linking of 2D sheets of inorganic graphene analogues and their potential applications.

Covalent cross-linking of 2D structures such as graphene, MoS₂ and C₃N₄ using coupling reactions affords the generation of novel materials with new or improved properties.

Covalent cross-linking as a strategy to generate novel materials based on layered (2D) and other low D structures

Covalent linking of 2D structures such as graphene, MoS₂and C₃N₄by employing coupling reactions provides a strategy to generate a variety of materials with new or improved properties.