Fast hydrogen purification through graphitic carbon nitride nanosheet membranes

Tailoring osteoimmunity and hemostasis using 3D-Printed nano-photocatalytic bactericidal scaffold for augmented bone regeneration

Bone hemorrhage, infection, and large bone defects following surgical treatment of traumatic bone injury have raised potential concerns, underscoring the urgent need to develop multifunctional therapeutic platforms that can effectively address traumatic bone regeneration. Advancements in three-dimensional (3D) printing technology have propelled the development of several engineering disciplines, such as tissue engineering. Nevertheless, 3D-printed frameworks with conventional materials often lack multifunctional capabilities to promote specific activities for diverse regeneration purposes. In this study, we developed a highly oxidized two-dimensional (2D) graphitic carbon nitride (Ox-gCN) as a nano-photocatalyst to reinforce alginate/gelatin (ALG)-based hydrogel scaffolds (ALG/CN) to achieve an anti-inflammatory and osteo-immunomodulatory niche with superior hemostatic ability for traumatic bone injury repair. Sulfuric acid oxidation enhances the oxygen-containing functional groups of the g-CN surface and promotes cell adhesion and differentiation of human bone marrow-derived mesenchymal stem cells (hBMSCs) in vitro. Moreover, the excellent visible light-activated photocatalytic characteristics of the ALG/CN scaffold were used in antibacterial studies. In addition, the ALG/CN bio/nanocomposite scaffold facilitates M2 polarization of macrophages than did pristine ALG scaffolds. Furthermore, ALG/CN scaffold induced hBMSCs differentiation by upregulating ERK and MAPKs phosphorylation during osteo-immunomodulation. In a rat calvaria defect model, the fabricated ALG/CN scaffolds induced new bone formation through collagen deposition and activation of osteocalcin proteins without inflammation in vivo. These results highlight the potential of 3D-printed functionalized 2D carbon nitrides in regulating the bone immune microenvironment, which may be beneficial for developing advanced tissue constructs, especially for traumatic bone regeneration in clinical settings.

Short-Side-Chain Membranes with Stabilized Superacid on Graphitic Carbon Nitride for Polymer Electrolyte Fuel Cells under Low-Humidity Conditions

The integration of superacid-like heteropolyacids offers a promising route to develop highly proton-conducting membranes for energy storage and conversion. However, the inherent hydrophilicity of these acids can cause leaching, which undermines the fuel cell performance. In our research, we engineered a proton-conductive membrane with a facile hydrothermal synthesis approach to form stabilized hybrid superacids, namely, phosphotungstic acid (PTA), with graphitic carbon nitride (PCN) and its incorporation in a short-side-chain ionomer, namely, Aquivion. This unique approach via PCN nanohybrids enhances the proton transport within the membrane. These nanohybrids effectively combined the strong acidity of PTA with continuous 2D proton-transport pathways via a short side chain, resulting in a notable proton conductivity of 0.228 S cm-1 at 80 °C under 95% relative humidity. The real impact was evident in the performance of fuel cells using the Aquivion/PCN nanocomposite membrane, which demonstrated a significant improvement of 34% in the peak power density (1.0 W cm-2), and 44% cell performance (0.98 A cm-2) was retained for the nanocomposite membrane at a low relatively humidity (30% RH) at 0.6 V. This advancement represents a major leap in energy conversion and storage technologies at low-humidity conditions.

Rational design of stable carbon nitride monolayer membranes for highly controllable CO2 capture and separation from CH4 and C2H2

CO2 capture and separation from natural and fuel gas are important industrial issues that refer to the control of CO2 emissions and the purification of target gases. Here, a novel non-planar g-C12N8 monolayer that could be synthesized via the supramolecular self-assembly strategy was identified using DFT calculations. The cohesive energy, phonon spectrum, BOMD, and mechanical stability criteria confirm the stability of the g-C12N8 monolayer. Our DFT calculations and MD simulations designate the g-C12N8 monolayer to perform as a superior CO2 separation membrane from CH4 and C2H2 gas owing to the high CO2 permeability and selectivity. Specifically, the CO2 permeability ranges from 1.21 × 107 to 1.53 × 107 GPU, while the selectivity of CO2/CH4 and CO2/C2H2 is 3.03 × 103 and 3.10 × 102 at 300 K, respectively, much higher than the Robeson upper bound and most of the reported 2D membranes, and even at high temperatures, the g-C12N8 monolayer-based CO2 separation membranes could operate with high performance. Further, at room temperature, the permeated CO2 gas can adsorb on the g-C12N8 surface with moderate adsorption energy and high capacity. These results indicate that the g-C12N8 membrane exhibits high performance for controlling CO2 capture and separation, which inevitably injects a new alternative of novel 2D membranes for CO2 separation and capture from CH4 and C2H2 in light of further experimental and theoretical research.

Triazole Drives Hole Localization and Superoxide Radical Formation for Enhancive Photocatalytic Cascade Isomerization/C─C Bond Scission of Biomass to Lactic Acid

Chemocatalytic synthesis of lactic acid (LA) from biomass sugars involves heat-absorbing multistep cascade reactions mediated by different active sites, often encountering unsatisfactory selectivity. Here, a hole-localized carbon nitride-based photocatalyst (C-CNN) is constructed by covalent binding of heptazine and triazole skeleton via C─N bonds and further conjugated interaction with activated carbon, achieving the complete conversion of various biomass sugars to LA (up to 98.6% selectivity) at room temperature for 2 h. The introduced triazole electron donor in C-CNN can not only enhance the adsorption of sugar for the enhanced aldose-to-ketose isomerization over the localized hole (Lewis acid) on the triazole skeleton, but also modulate the valence band oxidation to circumvent the formation of •OH but only •O2 ‒ for selective C3‒C4 cleavage of ketose, thus realizing the exclusive synthesis of LA. Moreover, near-infrared light absorption endowed by activated carbon can supply sufficient interface photothermal effect for ambient LA production. Life cycle assessment shows that the photocatalytic system has good prospects for industrialization in terms of both energy and environment. This work offers novel insights into the multidirectional utilization of solar energy for the value-added conversion of biomass through rational modulation of photothermal active sites.

Two-Dimensional Material-Based Nanofluidic Devices and Their Applications

Nanofluidics is an interdisciplinary field of study that bridges hydrodynamics, statistical physics, chemistry, materials science, biology, and other fields to investigate the transport of fluids and ions on the nanometric scale. The progress in this field, however, has been constrained by challenges in fabricating nanofluidic devices suitable for systematic investigations. Recent advances in two-dimensional (2D) materials have revolutionized the development of nanofluids. Their ultrathin structure and photothermoelectric response make it possible to achieve the scale control, friction limitation, and regulatory response, all of which are challenging to achieve with traditional solid materials. In this review, we provide a comprehensive overview of the preparation methods and corresponding structures of three types of 2D material-based nanofluidic devices, including nanopores, nanochannels, and membranes. We highlight their applications and recent advances in exploring physical mechanisms, detecting biomolecules (DNA, protein), developing iontronics devices, improving ion/gas selectivity, and generating osmotic energy. We discuss the challenges facing 2D material-based nanofluidic devices and the prospects for future advancements in this field.

Accurate stacking engineering of MOF nanosheets as membranes for precise H2 sieving

Two-dimensional (2D) metal-organic framework (MOF) nanosheet membranes hold promise for exact molecular transfer due to their structural diversity and well-defined in-plane nanochannels. However, achieving precise regulation of stacking modes between neighboring nanosheets in membrane applications and understanding its influence on separation performance remains unrevealed and challenging. Here, we propose a strategy for accurately controlling the stacking modes of MOF nanosheets via linker polarity regulation. Both theoretical calculations and experimental results demonstrate that a high linker polarity promotes neighboring nanosheets to a maximum AB stacking due to steric hindrance effects, leading to a controlled effective pore size of the membrane and consequently to improved molecular sieving. Among series of CuBDC-based 2D MOFs with different linkers, the CuBDC-NO2 nanosheet membranes exhibit a reduced effective stacking aperture of 0.372 nm, yielding H2 permeance of 4.44 × 10-7 mol m-2 s-1 Pa-1 with a high H2/CO2 and H2/CH4 selectivity of 266 and 536, respectively. This work represents the in-depth investigation of the accurate tuning of MOF nanosheet stacking in the field of 2D materials, offering more perspectives for broader applications with universality for various 2D materials.

Efficient Charge Separation in Ag/PCN/UPDI Ternary Heterojunction for Optimized Photothermal-Photocatalytic Performance via Tandem Electric Fields

Charge separation driven by the internal electric field is a research hotspot in photocatalysis. However, it remains challenging to accurately control the electric field to continuously accelerate the charge transfer. Herein, a strategy of constructing a tandem electric field to continuously accelerate charge transfer in photocatalysts is proposed. The plasma electric field, interface electric field, and intramolecular electric field are integrated into the Ag/g-C3N4/urea perylene imide (Ag/PCN/UPDI) ternary heterojunction to achieve faster charge separation and longer carrier lifetime. The triple electric fields function as three accelerators on the charge transport path, promoting the separation of electron-hole pairs, accelerating charge transfer, enhancing light absorption, and increasing the concentration of energetic electrons on the catalyst. The H2 evolution rate of Ag/PCN/UPDI is 16.8 times higher than that of pristine PDI, while the degradation rate of oxytetracycline is increased by 4.5 times. This new strategy will provide a groundbreaking idea for the development of high-efficiency photocatalysts.

Structural and Optical Characterization of Porous NiV2O6 Films Synthesized by Nebulizer Spray Pyrolysis for Photodetector Applications

NiV2O6 thin films were grown on glass slides with varying thicknesses using nebulizer spray pyrolysis. The impact of thickness on the thin films' optical, structural, morphological, and electrical characteristics was systematically investigated. X-ray diffraction and micro-Raman analysis confirmed the formation of the triclinic NiV2O6 system. Surface morphology and roughness variations in the as-deposited NiV2O6 films were studied using scanning electron microscopy (SEM) and a profilometer. Optical properties, including optical band gap (Eg), extinction coefficient (k), absorption coefficient (α), and refractive index (n), were determined through optical reflectance and transmittance measurements. The optical energy gap of the as-deposited NiV2O6 films decreased from 2.02 eV to 1.58 eV with increased layer thickness. Furthermore, the photo-detectivity of the films demonstrated an enhancement corresponding to the prolonged spray time. The sensitivity values obtained for visible irradiation were 328, 511, and 433 for samples S1, S2, and S3, respectively. The obtained results can be imputed to the specific porous microstructure.

Advancements in defect engineering of two-dimensional nanomaterial-based membranes for enhanced gas separation

The advent of two-dimensional nanomaterials, a revolutionary class of materials, is marked by their atomic-scale thickness, superior aspect ratios, robust mechanical attributes, and exceptional chemical stability. These materials, producible on a large scale, are emerging as the forefront candidates in the domain of membrane-based gas separation. The concept of defect engineering in 2D nanomaterials has introduced a novel approach in their application for membrane separation, offering an effective technique to augment the performance of these membranes. Nonetheless, the development of customized microstructures in gas separation membranes via defect engineering remains nascent. Hence, this review is designed to serve as a comprehensive guide for the application of defect engineering in 2D nanomaterial-based membranes. It delves into the most recent developments in this field, encompassing the synthesis methodologies of defective 2D nanomaterials and the mechanisms underlying gas transport. Special emphasis is placed on the utilization of defect-engineered 2D nanomaterial-based membranes in gas capture applications. Furthermore, the paper encapsulates the burgeoning challenges and prospective advancements in this area. In essence, defect engineering emerges as a promising avenue for enhancing the efficacy of 2D nanomaterial-based membranes in gas separation, offering significant potential for advancements in membrane-based gas separation technologies.

Guiding the Driving Factors on Plasma Super-Photothermal S-Scheme Core-Shell Nanoreactor to Enhance Photothermal Catalytic H2 Evolution and Selective CO2 Reduction

Light-induced heat has a non-negligible role in photocatalytic reactions. However, it is still challenging to design highly efficient catalysts that can make use of light and thermal energy synergistically. Herein, the study proposes a plasma super-photothermal S-scheme heterojunction core-shell nanoreactor based on manipulation of the driving factors, which consists of α-Fe2 O3 encapsulated by g-C3 N4 modified with gold quantum dots. α-Fe2 O3 can promote carrier spatial separation while also acting as a thermal core to radiate heat to the shell, while Au quantum dots transfer energetic electrons and heat to g-C3 N4 via surface plasmon resonance. Consequently, the catalytic activity of Au/α-Fe2 O3 @g-C3 N4 is significantly improved by internal and external double hot spots, and it shows an H2 evolution rate of 5762.35 µmol h-1 g-1 , and the selectivity of CO2 conversion to CH4 is 91.2%. This work provides an effective strategy to design new plasma photothermal catalysts for the solar-to-fuel transition.

Cation-Intercalated Clay-Based Two-Dimensional Membranes for Effective Desalination and Molecule Sieving

Montmorillonite (MMT) is known as an ion-exchangeable material, and cations between MMT nanosheets are easily exchanged by other cations. In this work, Ca2+, Fe3+, and Al3+ intercalated two-dimensional MMT membranes were developed by ion exchange of pristine MMT membranes (Na+-MMT), and their ion and dye removal abilities were investigated. The d-spacings of hydrated Fe3+ intercalated MMT membrane (Fe3+-MMT) and Al3+ intercalated MMT membrane (Al3+-MMT) were decreased compared with hydrated Na+-MMT membrane due to the stronger electrostatic attraction between Fe3+/Al3+ and negatively charged MMT nanosheets. Ion and dye sieving performances were improved significantly after the intercalation of Ca2+, Fe3+, and Al3+ into MMT membranes. Al3+-MMT membrane with a thickness of 1.17 μm could exclude 94% of Na+, and its ion sieving performance remained stable during a 120-h ion sieving experiment. Moreover, the rejection rate for rhodamine B (RB) reached 94% using an Al3+-MMT membrane with a thickness of 500 nm, and a water permeance of 73 L m-2 h-1 bar-1 was achieved. The excellent ion and dye sieving performances make it promising in the application of desalination and nanofiltration.

Tuning the Stacking Modes of Ultrathin Two-Dimensional Metal-Organic Framework Nanosheet Membranes for Highly Efficient Hydrogen Separation

Two-dimensional (2D) metal-organic framework (MOF) membranes are considered potential gas separation membranes of the next generation due to their structural diversity and geometrical functionality. However, achieving a rational structure design for a 2D MOF membrane and understanding the impact of MOF nanosheet stacking modes on membrane separation performance remain challenging tasks. Here, we report a novel kind of 2D MOF membrane based on [Cu2 Br(IN)2 ]n (IN=isonicotinato) nanosheets and propose that synergetic stacking modes of nanosheets have a significant influence on gas separation performance. The stacking of the 2D MOF nanosheets is controlled by solvent droplet dynamic behaviors at different temperatures of drop coating. Our 2D MOF nanosheet membranes exhibit high gas separation performances for H2 /CH4 (selectivity >290 with H2 permeance >520 GPU) and H2 /CO2 (selectivity >190 with H2 permeance >590 GPU) surpassing the Robeson upper bounds, paving a potential way for eco-friendly H2 separation.

Synthesis and up-to-date applications of 2D microporous g-C3N4 nanomaterials for sustainable development

In recent years, with the development of industrial technology and the increase of people's environmental awareness, the research on sustainable materials and their applications has become a hot topic. Among two-dimensional (2D) materials that have been selected for sustainable research, graphitic phase carbon nitride (g-C3N4) has become a hot research topic because of its many outstanding advantages such as simple preparation, good electrochemical properties, excellent photochemical properties, and better thermal stability. Nevertheless, the inherent limitations of g-C3N4 due to its relatively poor specific surface area, rapid charge recombination, limited light absorption range, and inferior dispersion in aqueous and organic media have limited its practical application. In the review, we summarize and analyze the unique structure of the 2D microporous nanomaterial g-C3N4, its synthesis method, chemical modification method, and the latest application examples in various fields in recent years, highlighting its advantages and shortcomings, with a view to providing ideas for overcoming the difficulties in its application. Furthermore, the pressing challenges faced by g-C3N4 are briefly discussed, as well as an outlook on the application prospects of g-C3N4 materials. It is expected that the review in this paper will provide more theoretical strategies for the future practical application of g-C3N4-based materials, as well as contributing to nanomaterials in sustainable applications.

High-Performance Alkali Metal Ion Storage in Bi2Se3 Enabled by Suppression of Polyselenide Shuttling Through Intrinsic Sb-Substitution Engineering

Bismuth selenide holds great promise as a kind of conversion-alloying-type anode material for alkali metal ion storage because of its layered structure with large interlayer spacing and high theoretical specific capacity. Nonetheless, its commercial development has been significantly hammered by the poor kinetics, severe pulverization, and polyselenide shuttle during the charge/discharge process. Herein, Sb-substitution and carbon encapsulation strategies are simultaneously employed to synthesize Sb_xBi_2-xSe₃ nanoparticles decorated on Ti₃C₂T_x MXene with encapsulation of N-doped carbon (Sb_xBi_2-xSe₃/MX⊂NC) as anodes for alkali metal ion storage. The superb electrochemical performances could be assigned to the cationic displacement of Sb³⁺ that effectively inhibits the shuttling effect of soluble polyselenides and the confinement engineering that alleviates the volume change during the sodiation/desodiation process. When used as anodes for sodium- and lithium-ion batteries, the Sb_0.4Bi_1.6Se₃/MX⊂NC composite exhibits superior electrochemical performances. This work offers valuable guidance to suppress the shuttling of polyselenides/polysulfides in high-performance alkali metal ion batteries with conversion/alloying-type transition metal sulfide/selenide anode materials.

Recent Advances in Carbon Nitride-Based S-scheme Photocatalysts for Solar Energy Conversion

Energy shortages are a major challenge to the sustainable development of human society, and photocatalytic solar energy conversion is a potential way to alleviate energy problems. As a two-dimensional organic polymer semiconductor, carbon nitride is considered to be the most promising photocatalyst due to its stable properties, low cost, and suitable band structure. Unfortunately, pristine carbon nitride has low spectral utilization, easy recombination of electron holes, and insufficient hole oxidation ability. The S-scheme strategy has developed in recent years, providing a new perspective for effectively solving the above problems of carbon nitride. Therefore, this review summarizes the latest progress in enhancing the photocatalytic performance of carbon nitride via the S-scheme strategy, including the design principles, preparation methods, characterization techniques, and photocatalytic mechanisms of the carbon nitride-based S-scheme photocatalyst. In addition, the latest research progress of the S-scheme strategy based on carbon nitride in photocatalytic H₂ evolution and CO₂ reduction is also reviewed. Finally, some concluding remarks and perspectives on the challenges and opportunities for exploring advanced nitride-based S-scheme photocatalysts are presented. This review brings the research of carbon nitride-based S-scheme strategy to the forefront and is expected to guide the development of the next-generation carbon nitride-based S-scheme photocatalysts for efficient energy conversion.