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As global demand for renewable energy and electric vehicles increases, the need for lithium has surged significantly. Extracting lithium from salt lake brine has become a cutting-edge technology in lithium resource production. In this study, two-dimensional (2D) GO/MXene composite membranes were fabricated using pressure-assisted filtration with a polyethyleneimine (PEI) coating, resulting in positively charged PEI-GO/MXene membranes. These innovative membranes, taking advantage of the synergistic effects of interlayer channel sieving and the Donnan effect, demonstrated excellent performance in Mg[sup.2+]/Li[sup.+] separation with a mass ratio of 20 (Mg[sup.2+] rejection = 85.3%, Li[sup.+] rejection = 16.7%, S[sub.Li,Mg] = 5.7) in simulated saline lake brine. Testing on actual salt lake brine in Tibet, China, confirmed the composite membrane’s potential for effective Mg[sup.2+]/Li[sup.+] separation. In the actual brine test with high concentration, Mg[sup.2+]/Li[sup.+] after membrane separation is 2.2, which indicates that the membrane can significantly reduce the concentration of Mg[sup.2+] in the brine. Additionally, the PEI-GO/MXene composite membrane demonstrated strong anti-swelling properties and effective divalent ion rejection. This research presents an innovative approach to advance the development of 2D membranes for the selective removal of Mg[sup.2+] and Li[sup.+] from salt lake brine.

Metal-organic framework (MOF) nanosheets and covalent organic framework (COF) nanosheets as emerging porous materials nanosheets have captured increasing attention owing to their attractive properties originating from the advantages of large lateral size, ultrathin thickness, tailorable physiochemical environment, flexibility and highly accessible active sites on surface, and the applications of them have been explored in a wide range of fields. Although MOF and COF nanosheets own many similar properties, their applications in various fields show significant differences, probably due to their different compositions and bonding modes. Hence, we summarize the recent progress of MOF and COF nanosheets by comparative analysis on their advantages and limitations in synthesis and applications, providing a more profound and full-scale perspective for researchers or beginners to understand this field. Herein, the categories of preparation methods of MOF and COF nanosheets are firstly discussed, including top-down and bottom-up methods. Secondly, the applications of MOF and COF nanosheets for separation, catalysis, sensing and energy storage are summarized. Finally, based on current achievements, we put forward our personal insights into the challenges and outlooks on the synthesis, characterizations, and promising applications for future research of MOF and COF nanosheets.

Shaping crystalline porous materials such as metal organic frameworks (MOFs) and zeolites into two-dimensional (2D) nanosheet forms is highly desirable for developing high-performance molecular sieving membranes. However, conventional exfoliation–deposition is complex and challenging for the large-scale fabrication of nanosheet MOF tubular membranes. Here, for the first time, we report a direct growth technique by ZnO self-conversion and ammonia assistance to fabricate zeolitic imidazolate framework (ZIF) membranes consisting of 2D nanosheets on porous hollow fiber substrates; the membranes are suitable for large-scale industrial gas separation processes. The proposed fabrication process for ZIF nanosheet membranes is based on the localized self-conversion of a pre-deposited thin layer of ZnO in a ligand solution containing ammonium hydroxide as a modulator. The resulting ZIF 2D nanosheet tubular membrane is highly oriented and only 50 nm in thickness. It exhibits excellent molecular sieving performance, with high H 2 permeance and selectivity for H 2 /CO 2 separation. This technique shows great promise in MOF nanosheet membrane fabrication for large-scale molecular sieving applications.

The growth of a Ni(OH) 2 coating on conductive carbon substrates is an efficient way to address issues related to their poor conductivity in electrochemical capacitor applications. However, the direct growth of nickel hydroxide coatings on a carbon substrate is challenging, because the surfaces of these systems are not compatible and a preoxidation treatment of the conductive carbon substrate is usually required. Herein, we present a facile preoxidation-free approach to fabricate a uniform Ni(OH) 2 coating on carbon nanosheets (CNs) by an ion-exchange reaction to achieve the in situ transformation of a MgO/C composite to a Ni(OH) 2 /C one. The obtained Ni(OH) 2 /CNs hybrids possess nanosheet morphology, a large surface area (278 m 2 /g), and homogeneous elemental distributions. When employed as supercapacitors in a three-electrode configuration, the Ni(OH) 2 /CNs hybrid achieves a large capacitance of 2,218 F/g at a current density of 1.0 A/g. Moreover, asymmetric supercapacitors fabricated with the Ni(OH) 2 /CNs hybrid exhibit superior supercapacitive performances, with a large capacity of 198 F/g, and high energy density of 56.7 Wh/kg at a power density of 4.0 kW/kg. They show excellent cycling stability with 93% capacity retention after 10,000 cycles, making the Ni(OH) 2 /CNs hybrid a promising candidate for practical applications in supercapacitor devices.

Graphene–amino acid interaction is gaining significance mainly based on its possible biomedicine applications. The density functional theory (DFT) calculation and molecular dynamics simulation (MD) are applied to obtain a comprehensive understanding of the adsorption mechanism of three kinds of amino acids, namely, alanine (Ala), glycine (Gly), and valine (Val) over the surface of graphene and functionalized graphene nanosheets. In this study, several analyses such as solvation energy, adsorption energy, intermolecular distances, and charge properties are used to explore the adsorption behavior of amino acid on the nanosheets. The calculated adsorption energies show that the interaction of amino acids with functionalized graphene is greater than the pristine graphene. Regarding DFT computations, the adsorption of Val on the graphene about − 10 kJ/mol is stronger than Gly and Ala. Meanwhile, it is found that the geometrical parameters and electronic properties of graphene change drastically upon functionalization, and the formation of hydrogen bonds between –COOH functional group and amino acids enhances the adsorption energy about 12–30%. To obtain a deeper comprehension of the interaction nature, the atoms in molecules (AIM) and the natural bond orbital (NBO) studies have been performed. Furthermore, the MD simulations are employed to assess the dynamic properties of our designed systems. The results from the present study demonstrate that the movement of the amino acids into the carriers is spontaneous and forms stable complexes.

Highlights Bimetallic nickel cobalt sulfide (Ni,Co)S 2 nanosheet arrays were demonstrated as a multifunctional catalyst for OER, HER, and ORR. First principle calculations were performed to probe the rate-limiting step, which involves the formation of *OOH from HO − on the (Ni,Co)S 2 surface. A water-splitting system was designed with the (Ni,Co)S 2 serving as both cathode and anode, and a Zn–air battery cathode electrocatalyst. The development of efficient earth-abundant electrocatalysts for oxygen reduction, oxygen evolution, and hydrogen evolution reactions (ORR, OER, and HER) is important for future energy conversion and energy storage devices, for which both rechargeable Zn–air batteries and water splitting have raised great expectations. Herein, we report a single-phase bimetallic nickel cobalt sulfide ((Ni,Co)S 2 ) as an efficient electrocatalyst for both OER and ORR. Owing to the synergistic combination of Ni and Co, the (Ni,Co)S 2 exhibits superior electrocatalytic performance for ORR, OER, and HER in an alkaline electrolyte, and the first principle calculation results indicate that the reaction of an adsorbed O atom with a H 2 O molecule to form a *OOH is the potential limiting step in the OER. Importantly, it could be utilized as an advanced air electrode material in Zn–air batteries, which shows an enhanced charge–discharge performance (charging voltage of 1.71 V and discharge voltage of 1.26 V at 2 mA cm −2 ), large specific capacity (842 mAh g Zn −1 at 5 mA cm −2 ), and excellent cycling stability (480 h). Interestingly, the (Ni,Co)S 2 -based Zn–air battery can efficiently power an electrochemical water-splitting unit with (Ni,Co)S 2 serving as both the electrodes. This reveals that the prepared (Ni,Co)S 2 has promising applications in future energy conversion and energy storage devices.

Carbon-free hydrogen as a promising clean energy source can be produced with electrocatalysts via water electrolysis. Oxygen evolution reaction (OER) as anodic reaction determines the overall efficiency of water electrolysis due to sluggish OER kinetics. Thus, it’s much desirable to explore the efficient and earth-abundant transition-metal-based OER electrocatalysts with high current density and superior stability for industrial alkaline electrolyzers. Herein, we demonstrate a significant enhancement of OER kinetics with the hybrid electrocatalyst arrays in alkaline via judiciously combining earth-abundant and ultrathin NiCo-based layered double hydroxide (NiCo LDH) nanosheets with nickel cobalt sulfides (NiCoS) with a facile metal-organic framework (MOF)-template-involved surface sulfidation process. The obtained NiCo LDH/NiCoS hybrid arrays exhibits an extremely low OER overpotential of 308 mV at 100 mA·cm −2 , 378 mV at 200 mA·cm −2 and 472 mV at 400 mA·cm −2 in 1 M KOH solution, respectively. A much low Tafel slope of 48 mV·dec −1 can be achieved. Meanwhile, with the current density from 50 to 250 mA·cm −2 , the NiCo-LDH/NiCoS hybrid arrays can run for 25 h without any degradation. Our results demonstrate that the construction of hybrid arrays with abundant interfaces of NiCo LDH/NiCoS can facilitate OER kinetics via possible modulation of binding energy of O-containing intermediates in alkaline media. The present work would pave the way for the development of low-cost and efficient OER catalysts and industrial application of water alkaline electrolyzers.

HighlightsA core-sheath structured coaxial composite fiber with highly aligned and densely stacked boron nitride nanosheets arrangements in the sheath was successfully fabricated.The coaxial fibers have an ultrahigh axial Herman orientation parameter of 0.81, thermal conductivity of 17.2 W m−1 K−1, and tensile strength of 192.5 MPa.The coaxial fibers exhibit intensively potential applications in the wearable thermal management textile.Hexagonal boron nitride nanosheets (BNNSs) exhibit remarkable thermal and dielectric properties. However, their self-assembly and alignment in macroscopic forms remain challenging due to the chemical inertness of boron nitride, thereby limiting their performance in applications such as thermal management. In this study, we present a coaxial wet spinning approach for the fabrication of BNNSs/polymer composite fibers with high nanosheet orientation. The composite fibers were prepared using a superacid-based solvent system and showed a layered structure comprising an aramid core and an aramid/BNNSs sheath. Notably, the coaxial fibers exhibited significantly higher BNNSs alignment compared to uniaxial aramid/BNNSs fibers, primarily due to the additional compressive forces exerted at the core-sheath interface during the hot drawing process. With a BNNSs loading of 60 wt%, the resulting coaxial fibers showed exceptional properties, including an ultrahigh Herman orientation parameter of 0.81, thermal conductivity of 17.2 W m−1 K−1, and tensile strength of 192.5 MPa. These results surpassed those of uniaxial fibers and previously reported BNNSs composite fibers, making them highly suitable for applications such as wearable thermal management textiles. Our findings present a promising strategy for fabricating high-performance composite fibers based on BNNSs.

Highlights The mixed-dimensional type II heterojunction of GaSb nanowires (NWs) and Bi 2 O 2 Se nanosheets (NSs) with a built-in electric field of ~ 140 meV is successfully constructed. As-fabricated NW/NS and NW array/NS mixed-dimensional heterojunction photodetectors exhibit as-expected high-performance self-powered photodetection behaviors, including ultralow I dark (0.07 and 0.08 pA), superior I light /I dark ratios (82 and 182) and ultrafast photoresponse (< 2/2 and 6/4 ms). As-fabricated NW array/NS mixed-dimensional heterojunction self-powered photodetector promises the future imaging and photocommunication. With high surface-to-volume ratio, the abundant surface states and high carrier concentration are challenging the near-infrared photodetection behaviors of narrow band gap semiconductors nanowires. In this study, the narrow band gap semiconductor of Bi 2 O 2 Se nanosheets (NSs) is adopted to construct mixed-dimensional heterojunctions with GaSb nanowires (NWs) for demonstrating the impressive self-powered NIR photodetection. Benefiting from the built-in electric field of ~ 140 meV, the as-constructed NW/NS mixed-dimensional heterojunction self-powered photodetector shows the low dark current of 0.07 pA, high I light / I dark ratio of 82 and fast response times of < 2/2 ms at room temperature. The self-powered photodetector performance can be further enhanced by fabricating the NW array/NS mixed-dimensional heterojunction by using a contact printing technique. The excellent photodetection performance promises the as-constructed NW/NS mixed-dimensional heterojunction self-powered photodetector in imaging and photocommunication.

The pollution of phenol wastewater is becoming worse. In this paper, a 2D/2D nanosheet-like ZnTiO3/Bi2WO6 S-Scheme heterojunction was synthesized for the first time through a two-step calcination method and a hydrothermal method. In order to improve the separation efficiency of photogenerated carriers, the S-Scheme heterojunction charge-transfer path was designed and constructed, the photoelectrocatalytic effect of the applied electric field was utilized, and the photoelectric coupling catalytic degradation performance was greatly enhanced. When the applied voltage was +0.5 V, the ZnTiO3/Bi2WO6 molar ratio of 1.5:1 had highest degradation rate under visible light: the degradation rate was 93%, and the kinetic rate was 3.6 times higher than that of pure Bi2WO6. Moreover, the stability of the composite photoelectrocatalyst was excellent: the photoelectrocatalytic degradation rate of the photoelectrocatalyst remained above 90% after five cycles. In addition, through electrochemical analysis, XRD, XPS, TEM, radical trapping experiments, and valence band spectroscopy, we found that the S-scheme heterojunction was constructed between the two semiconductors, which effectively retained the redox ability of the two semiconductors. This provides new insights for the construction of a two-component direct S-scheme heterojunction as well as a feasible new solution for the treatment of phenol wastewater pollution.