Organic Nanosheets Research Articles

A facile and scalable synthetic method for covalent organic nanosheets: ultrasonic polycondensation and photocatalytic degradation of organic pollutants.

Covalent organic framework nanosheets (COF NSs or CONs), as compared to their bulk counterparts two-dimensional (2D) covalent organic frameworks (COFs), exhibit superior performance in many aspects due to their fully accessible active sites benefiting from their ultrathin porous 2D structures. The development of a scalable synthetic methodology for CONs is crucial to further exploration of their unique properties and practical applications. Herein, we report an efficient strategy to fabricate ultrathin CONs through direct polycondensation of monomers under ultrasonic treatment and mild conditions. This method is facile and scalable, which is demonstrated by gram-scale synthesis of two ultrathin 2D CONs in several hours. Moreover, the as-prepared ultrathin CONs show excellent heterogeneous photocatalytic performance for the degradation of organic pollutants (dyes as representatives), remarkably superior to the bulk COFs prepared from the corresponding monomers under solvothermal conditions. This research provides a new roadmap for the scalable and facile synthesis of ultrathin CONs, which is of paramount importance for fully exploring the tremendous potential of this emerging type of 2D material.

Low-Potential-Driven Electrocatalytic Reduction of Co2 to Hydrocarbons by Cobalt-Based Metal−Organic Nanosheets

Low-Potential-Driven Electrocatalytic Reduction of Co2 to Hydrocarbons by Cobalt-Based Metal−Organic Nanosheets

Highly efficient removal of trace lead (II) from wastewater by 1,4-dicarboxybenzene modified Fe/Co metal organic nanosheets

• A novel Fe/Co metal organic nanosheet (FeCo@BDC) modified by 1,4-dicarboxybenzene (BDC) and triethylamine (TEA) was prepared. • FeCo@BDC achieved the highly efficient adsorption for trace Pb 2+ . • FeCo@BDC shows prominent regeneration performance. • The introduced BDC and TEA enhanced the removal performance. A novel Fe/Co metal organic complex nanosheet modified by 1,4-dicarboxybenzene (BDC), i.e., FeCo@BDC, was prepared, and highly efficient removal performance for trace lead (II) (Pb 2+ ) was demonstrated in the neutral aqueous solutions. The removal rates were higher than 95% and the adsorption was equilibrated in 15 min. The isotherms and kinetics for the adsorption Pb 2+ by the FeCo@BDC adsorbents followed Langmuir model and pseudo-second-order model, respectively. The maximum adsorption capacity was 220.48 mg g −1 . The FeCo@BDC adsorbents also own a prominent regeneration performance. The prominent performance of in the removal of trace Pb 2+ makes FeCo@BDC an ideal candidate as commercial adsorbent materials.

Pd/Ni-metal-organic framework-derived porous carbon nanosheets for efficient CO oxidation over a wide pH range.

Metal nanocrystal ornamented metal-organic frameworks (MOFs) are of particular interest in multidisciplinary applications; however, their electrocatalytic CO oxidation performance over wide pH ranges is not yet reported. Herein, Ni-MOF-derived hierarchical porous carbon nanosheets (Ni-MOF/PC) with abundant Ni-N x sites decorated with Pd nanocrystals (Pd/Ni-MOF/PC) were synthesized by microwave-irradiation (MW-I) followed by annealing at 900 °C and subsequent etching of Ni-MOF/C prior to Pd deposition. The fabrication mechanism comprises the generation of self-reduced reducing gases from triethylamine during the annealing and selective chemical etching of Ni, thereby facilitating the reduction of Ni-anchored MOF and Pd nanocrystal deposition with the aid of ethylene glycol and MW-I to yield Pd/Ni-N x enriched MOF/PC. The synthetic strategies endear the Pd/Ni-MOF/PC with unique physicochemical merits: abundant defects, interconnected pores, high electrical conductivity, high surface area, Ni-deficient but more active sites for Pd/Ni-N x in porous carbon nanosheets, and synergism. These merits endowed the CO oxidation activity and stability on Pd/Ni-MOF/PC substantially than those of Pd/Ni-MOF/C and Pd/C catalysts in wide pH conditions (i.e., KOH, HClO4, and NaHCO3). The CO oxidation activity study reveals the utilization of MOF/PC with metal nanocrystals (Pd/Ni) in CO oxidation catalysis.

Bimetallic sulfide particles incorporated in Fe/Co-based metal–organic framework ultrathin nanosheets toward boosted electrocatalysis of the oxygen evolution reaction

CoFe-MS/MOF nanocatalysts consisting of interconnected MOF ultrathin nanosheets doped with metal sulfide particles are prepared via a facile one-step solvothermal method as efficient electrocatalysts for the OER.

Redox-driven strong interfacial interactions between MnO2 and covalent organic nanosheets for efficient oxygen reduction electrocatalysis

An optimum weight fraction of manganese oxides is hybridized with covalent organic nanosheets (CONs) by redox reactions. The optimized hybrid exhibits the facile electron transfer to catalytic sites on manganese oxides for oxygen reduction reaction.

Long-life superlithiation of few-layered covalent organic nanosheets via graphene quantum dots/carbon nanotube stabilized three-dimensional architecture

The graphene quantum dots/CNT stabilized few-layered hyper-conjugated covalent organic nanosheet is synthesized and exhibits excellent electrochemical performance for lithium-organic batteries.

Antimicrobial two-dimensional covalent organic nanosheets (2D-CONs) for the fast and highly efficient capture and recovery of phosphate ions from water

The retrieval of depleting resources from wastewater could help resolve the mounting demands for resources in our society.

Catalytic photo-redox of simulated air into ammonia over bimetallic MOFs nanosheets with oxygen vacancies

Solar-driven conversion of nitrogen (N2) into ammonia (NH3) is a promising alternative to the Haber-Bosch process, while still suffers from low conversion efficiency due to inactive NN bond. Herein, a novel pathway of photocatalytic air redox reaction (ARR) to ammonia via NO is proposed and tested over an effective catalyst of oxygen-vacancy-rich bimetallic Cu-Co organic framework ultrathin nanosheets (OVR-CuCo-MOFs NS) under visible light. The catalyst with unique oxygen defective sites shows an excellent NH3 synthesis rate from air (287.76 ± 7.02 μmol g-1·h-1), which is 5.4-fold higher than that from pure N2. Moreover, experiments and theoretical calculations indicate that the transformation of air mainly follows a redox pathway, in which N2 and O2 can be trapped at the oxygen vacancies to generate nitric oxide (*NO) and further be reduced to ammonia by visible light. The ARR process shows a lower barrier of free energies in the onset activation step (*N2 → *N-NO, −0.08 eV) and rate-limiting step (*NO → *NHO, 1.23 eV) compared with those of traditional nitrogen reduction (*N2 → *N-NH, 1.48 eV and H2N-NH2 → *NH2, 1.29 eV, respectively). This work provides a new and sustainable pathway for photo-driven ammonia synthesis.

Preparation of novel terephthalic acid modified Fe/Ni metal organic nanosheet with high adsorption performance for trace Pb2+

A triethylamine functionalized Fe/Ni metal organic nanosheet (FeNi@TPA) was synthesized and shows high adsorption performance for trace Pb2+ (Removal rate > 90%). Rapid adsorption was achieved which reached equilibrium within 45 min. Only by 15.27% the adsorption capacity for Pb2+ decreased in 5 cycles. The Pb2+ adsorption data of FeNi@TPA were well fitted by Langmuir isotherms model and pseudo-second-order kinetics model. The theoretical maximum adsorption capacity reaches 214.08 mg·g−1. The high Pb2+ adsorption performance of FeNi@TPA brings it a bright prospect in realistic production.

Selective Removal of Anionic Dyes by Metal–Organic Framework-Anchored CoAl-Layered Double Hydroxide Nanosheets

A copper terephthalate metal organic framework-anchored CoAl-layered double hydroxide nanocomposite [CoAl-LDH/Cu-(tpa) MOF] was synthesized by in situ nucleation and growth of crystalline Cu-(tpa) ...

Carbon spheres wrapped with 2D covalent organic polymer as lubricant additives for enhancing tribological properties

A facile and efficient hydrothermal strategy for producing carbon spheres (CS) wrapped with two-dimensional (2D) covalent organic polymer (CS/TriC) was accomplished. The CS/TriC particles shaped with a core-shell nanostructure were spherical, in which TriC nanosheets were connected to CS by C-N bonds. Wettability tests showed that the lipophilicity and polar forces of CS/TriC were greatly enhanced compared with functionalized-CS. Tribological tests showed that the coefficient of friction and wear rate were reduced by 21.1% and 38.1%, which were in line with the results of SEM and XPS analyses performed after tribotesting. These results showed that excellent lubrication performance of CS/TriC were due to synergistic effects of which CS loading effects and excellent adsorption performance of 2D covalent organic polymer nanosheets.

Co/Zn bimetal organic framework elliptical nanosheets on flexible conductive fabric for energy harvesting and environmental monitoring via triboelectricity

Flexible and portable power sources are imperative chunks of wearable electronic devices. Fabric-based triboelectric nanogenerators (TENGs) have become most promising energy sources for wearable electronic devices as they can generate electrical energy from biomechanical movements with great flexibility. In this study, a highly flexible Co/Zn bimetal organic framework based TENG (BMOF TENG) is fabricated. Facilely prepared Co/Zn BMOF nanosheets are coated on flexible conductive fabric (BMOF/FCF) and utilized as the tribo-positive material against PTFE/Al based tribo-negative material for the fabrication of the BMOF TENG. The content of Zn is varied from 0% to 50% to achieve superior electrical output and observed that the 15% of Zn is appropriate for superior electrical output. The open circuit voltage, the short circuit current, and the charge density of the BMOF TENG are increased from 11 V to 47 V, from 1.06 µA to 7 µA, and from 4 nC/cm 2 to ~17 nC/cm 2 , respectively when the Zn content is increased from 0% to 15%. Thus, the optimized content of Zn in Co/Zn BMOF helped to enhance the electrical output of the BMOF TENG by nearly 450%. The output power of the BMOF TENG is found to be 1.1 mW/m 2 at a load resistance of 2 MΩ. As the phenomenon of gas sensing is largely associated to the surface of the material, the advantage of unique surface features of the BMOF/FCF is utilized in sensing hazardous gases. The device has shown variations in its electrical output in the presence of air and targeted gas and the good selectivity towards ammonia at room temperature. Ultimately, the BMOF TENG proposed in this study can convert mechanical energy into electrical energy and can be employed as an ammonia sensor in environmental monitoring and food quality assessment. • For the first time, Co/Zn bimetal organic framework (BMOF) nanosheet coated fabric is used for TENG. • At the optimized content of Zn (15%) in Co/Zn BMOF, the BMOF TENG is generated enhanced electrical output. • Fabric based flexible BMOF TENG is successfully employed as a room temperature ammonia sensor. • The unique surface morphology of BMOF has helped to evince good sensing behavior of the device. • Proposed BMOF TENG is able to serve as an energy harvesting as well as environmental monitoring device.

Dithia-Crown-Ether Integrated Self-Exfoliated Polymeric Covalent Organic Nanosheets for Selective Sensing and Removal of Mercury

Divalent mercury (Hg2+) is highly toxic in nature and extensively found in different natural water bodies worldwide. Thus, rapid trace-level monitoring of Hg2+, as well as its effective removal fro...

Construction of Chemically Bonded Interface of Organic/Inorganic g-C3N4/LDH Heterojunction for Z-Schematic Photocatalytic H2 Generation.

The design and synthesis of a Z-schematic photocatalytic heterostructure with an intimate interface is of great significance for the migration and separation of photogenerated charge carriers, but still remains a challenge. Here, we developed an efficient Z-scheme organic/inorganic g-C3N4/LDH heterojunction by in situ growing of inorganic CoAl-LDH firmly on organic g-C3N4 nanosheet (NS). Benefiting from the two-dimensional (2D) morphology and the surface exposed pyridine-like nitrogen atoms, the g-C3N4 NS offers efficient trap sits to capture transition metal ions. As such, CoAl-LDH NS can be tightly attached onto the g-C3N4 NS, forming a strong interaction between CoAl-LDH and g-C3N4 via nitrogen–metal bonds. Moreover, the 2D/2D interface provides a high-speed channel for the interfacial charge transfer. As a result, the prepared heterojunction composite exhibits a greatly improved photocatalytic H2 evolution activity, as well as considerable stability. Under visible light irradiation of 4 h, the optimal H2 evolution rate reaches 1952.9 μmol g−1, which is 8.4 times of the bare g-C3N4 NS. The in situ construction of organic/inorganic heterojunction with a chemical-bonded interface may provide guidance for the designing of high-performance heterostructure photocatalysts.

Ionic covalent organic nanosheet anchoring discrete copper for efficient quasi-homogeneous photocatalytic proton reduction

Covalent organic nanosheets can be applied potentially to solar-to-hydrogen fuel conversion because of their long-range ordered structure and predictable regulation. Additionally, minor progress has been made in the precise synthesis of copper-loaded composite catalysts at the atomic level. Hence, we synthesized hybrid Cu@TpTG-iCON materials by anchoring copper(II) ions into the evenly dispersed tridentate chelation sites of the TpTG-iCON precursor, which maximized the exposure of active sites during the catalytic reaction. Taking advantage of the well-defined structural configuration and nanosheet morphology, the heterogeneous Cu@TpTG-iCON catalyst exhibited an excellent hydrogen evolution reaction (HER) rate and significant stability in a ternary photocatalytic system. The atomic-level coordination modulation strategy in the covalent organic nanosheet matrix successfully demonstrated here has made possible the synthesis of other non-precious metal-based hybrid materials, indicating a step forward in the generation of a recyclable and efficient HER catalyst.

MXene‐Coupled Sandwich‐Like Polyaniline as Dual Conductive Electrode for Flexible All‐Solid‐State and Ionic‐liquid‐Based Supercapacitors with Superior Energy Density

Abstract2D conducting materials (2DCMs), such as graphene, coordination polymers including 2D‐metal‐organic frameworks, conducting organic polymer nanosheets, metal sheets, and their composites are promising candidates for energy storage and conversion applications. Rational design and preparation of 2DCMs usually involve specific templates (soft or hard) that often sacrifice conductivity and negatively impact the electrochemical charge storage performance. In this work, 2D MXene is used as the conductive substrate yielding sandwich‐like MXene‐polyaniline hybrids (MX@PANIs) for high‐performance supercapacitors (SCs) operating in aqueous, solid‐state, and ionic‐liquid‐based safe electrolytes. The MX@PANI‐based flexible all‐solid‐state SC using PVA‐H2SO4 delivers an excellent energy density of 28.6 W h kg–1 at 0.2 kW kg–1. Importantly, the synergistic effect of constituents in MX@PANI in ionic liquid (EMITFSI) electrolyte exhibits an impressive energy density performance of 139 W h kg–1 at a power density of 1.66 kW kg–1, exceeding most of the reported PANI and MXene‐based SCs. This piece of work offers a feasible solution to create the next generation energy‐storage devices using novel 2D hybrid nanocomposites working in safer electrolytes for high‐performance SCs.

Construction of a photothermal hydrogel platform with two-dimensional PEG@zirconium-ferrocene MOF nanozymes for rapid tissue repair of bacteria-infected wounds

Because of increasing antibiotic resistance, careful construction of an efficient phototherm-nanozyme-hydrogel synergistic antibacterial platform is imperative for the treatment of bacteria-infected wounds. In this study, a carrageenan-based hydrogel embedded with polyethylene glycol dicarboxylic acid (COOH-PEG-COOH)-functionalized zirconium-ferrocene metal-organic frames nanosheets (PEG@Zr-Fc MOF hydrogel) was successfully constructed through COOH-PEG-COOH modification and physical assembly. The PEG@Zr-Fc MOF hydrogel could capture Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria through reactive oxygen species (ROS) destruction and kill some bacteria by disintegration of H2O2 into toxic hydroxyl radicals (•OH). Significantly, by introducing the photothermal performance of the PEG@Zr-Fc MOF hydrogel, the catalytic activity of the target material could be improved to achieve a synergistic sterilization effect. The wound infection model experiment confirmed that the PEG@Zr-Fc MOF hydrogel had powerful bactericidal activity and could achieve a rapid tissue repair effect. More importantly, the PEG@Zr-Fc MOF hydrogel had negligible biological toxicity and reduced the risk of inflammation. This study reveals that phototherm-nanozyme-hydrogel synergy holds great potential for bacterial wound infection therapy. Additionally, this is the first study to use two-dimensional MOF nanozymes in combination with hydrogel for antimicrobial therapy. Statement of significanceBacteria-infected wound is one of the serious threats to public health, and this topic has attracted tremendous attention worldwide in recent decades. Although numerous traditional therapeutic strategies that depend on antibiotics have been developed and applied for treating bacteria-infected wound disease, the effect of wound treatment is becoming increasingly unsatisfactory due to bacterial resistance. The present study provides a feasible method to treat bacterial wound infection by constructing a carrageenan-based hydrogel embedded with polyethylene glycol dicarboxylic acid (COOH-PEG-COOH) functionalized zirconium-ferrocene metal organic frame nanosheets (PEG@Zr-Fc MOF hydrogel). The experiments with the wound infection model confirmed that the PEG@Zr-Fc MOF hydrogel had powerful bactericidal activity and could achieve a rapid tissue repair. This strategy provides a promising avenue to further accelerate the development of antibacterial therapy in biomedical fields.

Mechanochemical Construction 2D/2D Covalent Organic Nanosheets Heterojunctions Based on Substoichiometric Covalent Organic Frameworks.

Combining different semiconductor materials to construct heterojunctions is a promising method to achieve efficient photocatalysis; however, it is still a challenge to accurately construct heterojunctions through molecular regulation. In this work, we take advantage of the remaining aldehyde groups in a substoichiometric covalent organic framework (denoted as PTO-COF) to achieve precise construction of covalently linked 2D/2D covalent organic nanosheets (CONs) heterojunctions through mechanochemical methods. The ultrathin structure of CONs endowed them with superior photoinduced charge generation and separation. Additionally, the energy bands of two CONs materials in heterojunctions were precisely coupled in a Z-scheme by the well-designed covalent linkages, which lead to a 190% enhancement of photocatalytic degradation efficiency for PTO/TpMa CONs heterojunctions as compared with pure COFs. This work provides new insights for design and synthesis of innovative 2D organic heterojunction photocatalysts.

Bimetallic organic frame nanosheet fluorescent probe used for detecting tetracycline and folic acid

A novel and powerful dual-signal fluorescence measurement method was developed to detect the content of tetracycline (TC) and folic acid (FA) based on the change of the fluorescence signal of the bimetallic Ag@Cu MOFs nanosheet fluorescent probe. Bimetallic Ag@Cu MOFs nanosheets have high fluorescence intensity and good fluorescence stability. By adding TC, the fluorescence signal intensity of the probe is quenched obviously, but the signal intensity is greatly enhanced by adding FA. Based on this, the developed dual-signal fluorescence detection method can detect TC and FA with high sensitivity and selectivity, which can afford a new idea for dual-signal micro-detection by a fast, simple, and reliable method.