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Abstract The urgent demand for addressing dye contaminants in water necessitates the development of microrobots that exhibit remote navigation, rapid removal, and molecular identification capabilities. The progress of microrobot development is currently hindered by the scarcity of multifunctional materials. In this study, a plasmonic MXene hydrogel (PM‐Gel) is synthesized by combining bimetallic nanocubes and Ti3C2Tx MXene through the rapid gelation of degradable alginate. The hydrogel can efficiently adsorb over 60% of dye contaminants within 2 min, ultimately achieving a removal rate of >90%. Meanwhile, the hydrogel exhibits excellent sensitivity in surface enhanced Raman scattering (SERS) detection, with a limit of detection (LOD) as low as 3.76 am. The properties of the plasmonic hydrogel can be further adjusted for various applications. As a proof‐of‐concept experiment, thermosensitive polymers and superparamagnetic particles are successfully integrated into this hydrogel to construct a versatile, light‐responsive microrobot for dye contaminants. With magnetic and optical actuation, the robot can remotely sample, identify, and remove pollutants in maze‐like channels. Moreover, light‐driven hydrophilic‐hydrophobic switch of the microrobots through photothermal effect can further enhance the adsorption capacity and reduced the dye residue by up to 58%. These findings indicate of a broad application potential in complex real‐world environments.

Abstract Photocatalytic carbon dioxide (CO2) reduction is an effective method for in vivo carbon monoxide (CO) generation for antibacterial use. However, the available strategies mainly focus on utilizing visible‐light‐responsive photocatalysts to achieve CO generation. The limited penetration capability of visible light hinders CO generation in deep‐seated tissues. Herein, a photothermal CO2 catalyst (abbreviated as NNBCs) to achieve an efficient hyperthermic effect and in situ CO generation is rationally developed, to simultaneously suppress bacterial proliferation and relieve inflammatory responses. The NNBCs are modified with a special polyethylene glycol and further embellished by bicarbonate (BC) decoration via ferric ion‐mediated coordination. Upon exposure to 1064 nm laser irradiation, the NNBCs facilitated efficient photothermal conversion and in situ CO generation through photothermal CO2 catalysis. Specifically, the photothermal effect accelerated the decomposition of BC to produce CO2 for photothermal catalytic CO production. Benefiting from the hyperthermic effect and in situ CO production, in vivo assessments using an osteomyelitis model confirmed that NNBCs can simultaneously inhibit bacterial proliferation and attenuate the photothermal effect‐associated pro‐inflammatory response. This study represents the first attempt to develop high‐performance photothermal CO2 nanocatalysts to achieve in situ CO generation for the concurrent inhibition of bacterial growth and attenuation of inflammatory responses.

Abstract The recent progress on the liquid crystalline (LC) dispersion of two‐dimensional (2D) transition metal carbides (MXenes) has propelled this unique nanomaterial into a realm of high‐performance architectures, such as films and fibers. Additionally, compared to architectures made from typical non‐LC dispersions, those derived from LC MXene possess tunable ion transport routes and enhanced conductivity and physical properties, demonstrating great potential for a wide range of applications, such as electronic displays, smart glasses, and thermal camouflage devices. This review provides an overview of the progress achieved in the production and processing of LC MXenes, including critical discussions on satisfying the required conditions for LC formation. It also highlights how acquiring LC MXenes has broadened the current solution‐based manufacturing paradigm of MXene‐based architectures, resulting in unprecedented performances in their conventional applications (e.g., energy storage and strain sensing) and in their emerging uses (e.g., tribology). Opportunities for innovation and foreseen challenges are also discussed, offering future research directions on how to further benefit from the exciting potential of LC MXenes with the aim of promoting their widespread use in designing and manufacturing advanced materials and applications.

Abstract Freestanding MXene‐based macroforms have gained significant attention as versatile components in electrochemical energy storage applications owing to their interconnected conductive network, strong mechanical strength, and customizable surface chemistries derived from MXene nanosheets. This comprehensive review article encompasses key aspects related to the synthesis of MXene nanosheets, strategies for structure design and surface medication, surface modification, and the diverse fabrication methods employed to create freestanding MXene‐based macroform architectures. The review also delves into the recent advancements in utilizing freestanding MXene macroforms for electrochemical energy storage applications, offering a detailed discussion on the significant progress achieved thus far. Notably, the correlation between the macroform's structural attributes and its performance characteristics is thoroughly explored, shedding light on the critical factors influencing efficiency and durability. Despite the remarkable development, the review also highlights the existing challenges and presents future perspectives for freestanding MXene‐based macroforms in the realms of high‐performance energy storage devices. By addressing these challenges and leveraging emerging opportunities, the potential of freestanding MXene‐based macroforms can be harnessed to enable groundbreaking advancements in the field of energy storage.

Abstract Aqueous zinc‐ion batteries (AZIBs) are gaining popularity for their cost‐effectiveness, safety, and utilization of abundant resources. MXenes, which possess outstanding conductivity, controllable surface chemistry, and structural adaptability, are widely recognized as a highly versatile platform for AZIBs. MXenes offer a unique set of functions for AZIBs, yet their significance has not been systematically recognized and summarized. This review article provides an up‐to‐date overview of MXenes‐based electrode materials for AZIBs, with a focus on the unique functions of MXenes in these materials. The discussion starts with MXenes and their derivatives on the cathode side, where they serve as a 2D conductive substrate, 3D framework, flexible support, and coating layer. MXenes can act as both the active material and a precursor to the active material in the cathode. On the anode side, the functions of MXenes include active material host, zinc metal surface protection, electrolyte additive, and separator modification. The review also highlights technical challenges and key hurdles that MXenes currently face in AZIBs.

Abstract Since the initial discovery of Ti3C2 a decade ago, there has been a significant surge of interest in 2D MXenes and MXene‐based composites. This can be attributed to the remarkable intrinsic properties exhibited by MXenes, including metallic conductivity, abundant functional groups, unique layered microstructure, and the ability to control interlayer spacing. These properties contribute to the exceptional electrical and mechanical performance of MXenes, rendering them highly suitable for implementation as candidate materials in flexible and wearable energy storage devices. Recently, a substantial number of novel research has been dedicated to exploring MXene‐based flexible materials with diverse functionalities and specifically designed structures, aiming to enhance the efficiency of energy storage systems. In this review, a comprehensive overview of the synthesis and fabrication strategies employed in the development of these diverse MXene‐based materials is provided. Furthermore, an in‐depth analysis of the energy storage applications exhibited by these innovative flexible materials, encompassing supercapacitors, Li‐ion batteries, Li–S batteries, and other potential avenues, is conducted. In addition to presenting the current state of the field, the challenges encountered in the implementation of MXene‐based flexible materials are also highlighted and insights are provided into future research directions and prospects.

Abstract The concept of “green‐ammonia‐zero‐carbon emission” is an emerging research topic in the global community and many countries driving toward decarbonizing a diversity of applications dependent on fossil fuels. In light of this, electrochemical nitrogen reduction reaction (ENRR) received great attention at ambient conditions. The low efficiency (%) and ammonia (NH3) production rates are two major challenges in making a sustainable future. Besides, hydrogen evolution reaction is another crucial factor for realizing this NH3 synthesis to meet the large‐scale commercial demand. Herein, the (i) importance of NH3 as an energy carrier for the next future, (ii) discussion with ENRR theory and the fundamental mechanism, (iii) device configuration and types of electrolytic systems for NH3 synthesis including key metrics, (iv) then moving into rising electrocatalysts for ENRR such as single‐atom catalysts (SACs), MXenes, and metal–organic frameworks that were scientifically summarized, and (v) finally, the current technical contests and future perceptions are discussed. Hence, this review aims to give insightful direction and a fresh motivation toward ENRR and the development of advanced electrocatalysts in terms of cost, efficiency, and technologically large scale for the synthesis of green NH3.

Abstract MXene‐supported noble metal alloy catalysts exhibit remarkable electrocatalytic activity in various applications. However, there is no facile one‐step method for synthesizing these catalysts, because the synthesis of MXenes requires a strongly oxidizing environment and the preparation of platinum nanoalloys requires a strongly reducing environment and high temperatures. Hence, achieving coupling in one step is extremely challenging. In this paper, a straightforward one‐step molten salt method for preparing MXene‐supported platinum nanoalloy catalysts is proposed. The molten salt acts as the reaction medium to dissolve the transition metals and platinum ions at high temperatures. Transition metal ions oxidize the A‐site element from its MAX precursor at high temperatures, and the resulting transition metals further reduce platinum ions to form alloys. By coupling Al oxidation and platinum ion reduction using a molten salt solvent, this method directly converts Ti3AlC2 to a Pt‐M@Ti3C2Tx catalyst (where M denotes the transition metal). It further offers the possibility of extending the Pt‐M phase to binary, ternary, or quaternary platinum‐containing nanoalloys and converting the Al‐containing MAX phase to Ti2AlC and Ti3AlCN. Due to the strong interfacial interaction, the as‐prepared Pt‐Co@Ti3C2Tx is superior to commercial Pt/C (20 wt.%) in the hydrogen evolution reaction.

Abstract Surface chemistry of MXenes is of significant interest due to its potential to control their final optoelectronic and physicochemical properties, and address the oxidation and dispersion stabilities of MXenes. Surface chemistry of MXenes can be manipulated by either MXene synthesis via chemical etching or post surface functionalization method. Although numerous reviews have explored MXene synthesis methods, there has been a lack of focus on post surface functionalization. This review aims to fill this gap by summarizing recent advancements in the MXene surface functionalization chemistry, and elucidating mechanisms, properties, and future perspectives of functionalized MXenes. We discuss organic ligand molecules, such as organic salts, catechols, phosphonates, carboxylates, and silanes, which can be employed to surface‐functionalize MXene through covalent or non‐covalent bond interaction. This comprehensive review offers valuable insights for scientists and engineers in utilizing functionalized MXenes across diverse applications, including EMI shielding, energy storage, electronics, optoelectronics, and sensors.

Abstract MXenes are mentioned in many applications due to their unique properties. However, the traditional etching method has a lengthy synthesis time, dangerous process, and high cost. Molten salt etching is not only short in time but also safe and simple, laying a good foundation for industrialization. Here, we compare the traditional F‐containing etching method with the molten salt etching method. Transmission electron microscopy elemental mapping images and X‐ray photoelectron spectroscopy show that the Ti3C2Tx surface end of traditional etching is terminated by –F, while the Ti3C2Tx surface end of molten salt etching is terminated by –Cl. Finally, the sodium‐ion batteries are fabricated and the performance difference of the three etching methods is compared. The results show that the capacity of 102.1 mAh g–1 can still be reached when the molten salt etching MXene material returns to 0.1 A g–1 after the current density of 5 A g–1. After 500 cycles at 1 A g–1, there is no significant loss of capacity and the Coulomb efficiency is close to 100%. This work describes that molten salt etching MXene has comparable sodium storage capacity to conventional F‐containing etched MXene, making it a potential candidate for the production of large‐scale sodium‐ion batteries.

Abstract Solar evaporation is a facile and promising technology to efficiently utilize renewable energy for freshwater production and seawater desalination. Here, the fabrication of self‐regenerating hydrogel composed of 2D‐MXenes nanosheets embedded in perovskite La 0.6Sr 0.4Co 0.2Fe 0.8O3−δ (LSCF)/polyvinyl alcohol hydrogels for efficient solar‐driven evaporation and seawater desalination is reported. The mixed dimensional LSCF/Ti3C2 composite features a localized surface plasmonic resonance effect in the polymeric network of polyvinyl alcohol endows excellent evaporation rates (1.98 kg m−2 h−1) under 1 k Wm−2 or one sun solar irradiation ascribed by hydrophilicity and broadband solar absorption (96%). Furthermore, the long‐term performance reveals smooth mass change (13.33 kg m−2) during 8 h under one sun. The composite hydrogel prompts the dilution of concentrated brines and redissolves it back to water (1.2 g NaCl/270 min) without impeding the evaporation rate without any salt‐accumulation. The present research offers a substantial opportunity for solar‐driven evaporation without any salt accumulation in real‐life applications.

Abstract Electrocatalytic nitrogen reduction reaction (NRR) represents a promising sustainable approach for NH3 synthesis. However, the poor NRR performance of electrocatalysts is a great challenge at this stage, mainly owing to their low activity and the competitive hydrogen evolution reaction (HER). Herein, 2D ferric covalent organic framework/MXene (COF‐Fe/MXene) nanosheets with controllable hydrophobic behaviors are successfully prepared via a multiple‐in‐one synthetic strategy. The boosting hydrophobicity of COF‐Fe/MXene can effectively repel water molecules to inhibit the HER for enhanced NRR performances. By virtue of the ultrathin nanostructure, well‐defined single Fe sites, nitrogen enrichment effect, and high hydrophobicity, the 1H,1H,2H,2H‐perfluorodecanethiol modified COF‐Fe/MXene hybrid shows a NH3 yield of 41.8 µg h−1 mgcat.−1 and a Faradaic efficiency of 43.1% at −0.5 V versus RHE in a 0.1 m Na2SO4 water solution, which are vastly superior to the known Fe‐based catalysts and even to the noble metal catalysts. This work provides a universal strategy to design and synthesis of non‐precious metal electrocatalysts for high‐efficiency N2 reduction to NH3.

Abstract In past decades, high‐entropy (HE) materials, containing five or more elements with approximately equal atomic ratio, are extensively investigated due to their desirable properties in a series of applications. Recently, HE two‐dimensional (2D) materials have become promising materials, which not only endow the advantages from their bulk form but also exhibit unusual properties due to their 2D features. So far, the HE 2D transition metal carbides (MXenes), dichalcogenides (TMDs), hydrotalcites (LDHs), and oxides have been successfully synthesized and performed well in different electrochemical reactions, which is originated from the synergistic effect of multicomponents and atomic thin characteristics. Here, the challenges on processing, characterization, and property predictions of HE 2D materials are emphasized. Finally, viable strategies, advanced processing, fundamental understanding, in‐depth characterization of new HE 2D materials are proposed.

Abstract Currently, emerging battery technologies are being studied intensively. The lack of ideal electrode materials remains a key hindrance to further development of new batteries. The novel MXene material, due to its unique structural characteristics and physicochemical properties, shows the ability to enhance the electrochemical performance of the electrode. In addition to the adjustable layer spacing, because of excellent electrical conductivity, rich chemical composition, and controllable surface chemistry, MXene has the potential for use in diverse applications as an ideal electrode material in various battery systems. This review covers the recent progress achieved in research of the zinc‐ion energy storage of MXenes, including MXene‐based cathodes, MXene‐derived cathodes, MXene‐modified zinc anodes, and electrolyte additives. Moreover, further structural design and reaction mechanisms of MXenes in zinc‐ion storage are explored.

Abstract One of the most exciting new developments in energy storage technology is flexible Zn‐ion hybrid supercapacitors (f‐ZIHSCs), which combine the high energy of Zn‐ion batteries with high‐power supercapacitors to satisfy the needs of portable flexible electronics. However, the development of f‐ZHSCs is still in its infancy, and there are numerous barriers to overcome before they can be widely implemented for practical applications. This review gives an up‐to‐date description of recent achievements and underlying concepts in energy storage mechanisms of f‐ZIHSCs and emphasizes the critical role of cathode, anode, and electrolyte materials systems in speeding the prosperity of f‐ZIHSCs. The innovative nanostructured‐based cathode materials for f‐ZIHSCs include carbon (e.g., porous carbon, heteroatom‐doped carbon, biomass‐derived porous carbon, graphene, etc.), metal‐oxides, MXenes, and metal/covalent‐organic frameworks, and other materials (e.g., activated carbon, phosphorene, etc.) are mainly focused. Afterward, the latest developments in flexible anode and electrolyte frameworks and impacts of electrolyte compositions on the electrochemical properties of f‐ZIHSC are elaborated. Subsequently, the advancements based on fabrication designs, including quasi‐solid‐state, micro, fiber‐shaped, and all climate‐changed f‐ZIHSCs, are discussed in detail. Lastly, a summary of current challenges and recommendations for the future progress of advanced f‐ZIHSC are addressed. This review article is anticipated to further understand the viable strategies and achievable approaches for assembling high‐performance f‐ZIHSCs and boost the technical revolutions on cathode, anode, and electrolytes for f‐ZIHSC devices.

Herein, we present a density functional theory with dispersion correction (DFT-D) calculations that focus on the intercalation of ionic liquids (ILs) electrolytes into the two-dimensional (2D) Ti 3 C 2 T x MXenes. These ILs include the cation 1-ethyl-3-methylimidazolium (Emim + ), accompanied by three distinct anions: bis(trifluoromethylsulfonyl)imide (TFSA - ), (fluorosulfonyl)imide (FSA - ) and fluorosulfonyl(trifluoromethanesulfonyl)imide (FTFSA - ). By altering the surface termination elements, we explore the intricate geometries of IL intercalation in neutral, negative, and positive pore systems. Accurate estimation of charge transfer is achieved through five population analysis models, such as Hirshfeld, Hirshfeld-I, DDEC6 (density derived electrostatic and chemical), Bader, and VDD (voronoi deformation density) charges. In this work, we recommend the DDEC6 and Hirshfeld-I charge models, as they offer moderate values and exhibit reasonable trends. The investigation, aimed at visualizing non-covalent interactions, elucidates the role of cation-MXene and anion-MXene interactions in governing the intercalation phenomenon of ionic liquids within MXenes. The magnitude of this role depends on two factors: the specific arrangement of the cation, and the nature of the anionic species involved in the process., (© 2024 Wiley Periodicals LLC.)

Abstract Heteroatom nitrogen doping in two‐dimensional transition metal carbides, known as MXenes, has been considered as a promising strategy for modulating their electronic structure and electrochemical reactivity. While high‐temperature annealing in the presence of a nitrogen source has been one popular method to introduce nitrogen, annealing exfoliated multilayered MXenes typically brings about incomplete delamination and the treatment of delaminated monolayer MXenes often leads to irreversible restacking. Here, starting from the typical carbide precursor, we developed an aqueous colloid containing monolayered nitrogen‐doped titanium carbide sheets with excellent dispersity and stability. This achievement is critically dependent on the retaining of the hydrophilic surface of host layers during annealing treatment. The successful realization of nitrogen doping into individual MXene monolayers resulted in enhanced electrical conductivity and redox reactivity, for which the sample exhibited excellent capacitive electrochemical performance (586 F/g at a scan rate of 5 mV/s) and cycling stability (capacitance retention of 96.2% after 104 cycles at 5 A/g). This paper presents a feasible and simple strategy for designing nitrogen‐doped MXenes colloid, the realization of which promises its facile uses in liquid phase engineering techniques toward versatile applications.

Abstract With a decade of effort, significant progress has been achieved in the synthesis, processing, and applications of MXenes. Metal ions play many crucial roles, such as in MXene delamination, structure regulation, surface modification, MXene composite construction, and even some unique applications. The different roles of metal ions are attributed to their many interactions with MXenes and the unique nature of MXenes, including their layered structure, surface chemistry, and the existence of multi‐valent transition metals. Interactions with metal ions are crucial for the energy storage of MXene electrodes, especially in metal ion batteries and supercapacitors with neutral electrolytes. This review aims to provide a good understanding of the interactions between metal ions and MXenes, including the classification and fundamental chemistry of their interactions, in order to achieve their more effective utilization and rational design. It also provides new perspectives on MXene evolution and exfoliation, which may suggest optimized synthesis strategies. In this respect, the different effects of metal ions on MXene synthesis and processing are clarified, and the corresponding mechanisms are elaborated. Research progress on the roles metal ions have in MXene applications is also introduced.

Abstract Highly active two‐dimensional (2D) nanocomposites, integrating the unique merits of individual components and synergistic effects of composites, are greatly desired for flexible sensing device applications. Although 2D transition metal carbides and nitrides (MXenes) combined with their high metallic conductivity and versatile surface chemistry have shown its huge potential for sensing reactions, it still remains a major challenge to construct functional materials with intriguing sensing performance at room temperature (RT). Herein, we used an integration of density functional theory (DFT) simulations and bulk electrosensitive measurements to show high electrocatalytic sensitivity of polyaniline/MXene (PANI/Ti3C2T x) nanocomposites. Thanks to the synergistic properties of nanocomposites and high catalytic/absorption capacity of Ti3C2T x MXene, PANI nanoparticles are rationally decorated on Ti3C2T x nanosheet surface via in situ polymerization by low temperature approach to induce remarkable detection sensitivity, rapid response/recovery rate, and mechanical stability at RT. This study offers a versatile platform to use MXenes to fabricate 2D nanocomposites materials for high‐performance flexible gas sensors.

Abstract In recent years, MXene has become a hotspot because of its good conductivity, strong broadband absorption, and tunable band gap. In this contribution, 0D MXene Ti3C2Tx quantum dots are synthesized by a liquid exfoliation method and a wideband nonlinear optical response from 800 to 1550 nm is studied, which have a larger nonlinear absorption coefficient β of –(11.24 ± 0.14) × 10–2 cm GW–1. The carrier dynamic processes of 0D MXene are explored with ultrahigh time resolution nondegenerate transient absorption (TA) spectroscopy, which indicates that the TA signal reaches its maximum in 1.28 ps. Furthermore, 0D MXene is used to generate ultrashort pulses in erbium or ytterbium‐doped fiber laser cavity. High signal‐to‐noise (72 dB) femtosecond lasers with pulse durations as short as 170 fs with spectrum bandwidth of 14.8 nm are obtained. Finally, an ultranarrow fiber laser based on 0D MXene is also investigated and has a full width at half maximum of only 5 kHz, and the power fluctuation is less than 0.75% of the average power. The experimental works prove that 0D MXene is an excellent SA and has a promising application in ultrafast and ultranarrow photonics.

Abstract 2D transition metal carbides, nitrides, and carbonitrides called MXenes show outstanding performance in many applications due to their superior physical and chemical properties. Herein, a ZnO–MXene mixture with different contents of Ti3C2 is applied as electron transport layers (ETLs) and the influence of the Ti3C2 MXene in all‐inorganic metal halide perovskite nanocrystal light‐emitting diodes (perovskite NC LEDs) is explored. The addition of Ti3C2 makes more balanced charge carrier transport in LEDs by changing the energy level structure and electron mobility of ETL. Moreover, lower surface roughness is obtained for the ETL, thus guaranteeing uniform distribution of the perovskite NCs layer and further reducing leakage current. As a result, a 17.4% external quantum efficiency (EQE) with low efficiency roll‐off is achieved with 10% Ti3C2, which is a 22.5% improvement compared to LEDs without Ti3C2.

Abstract Designing lightweight nanostructured aerogels for high‐performance electromagnetic interference (EMI) shielding is crucial yet challenging. Ultrathin cellulose nanofibrils (CNFs) are employed for assisting in building ultralow‐density, robust, and highly flexible transition metal carbides and nitrides (MXenes) aerogels with oriented biomimetic cell walls. A significant influence of the angles between oriented cell walls and the incident EM wave electric field direction on the EMI shielding performance is revealed, providing an intriguing microstructure design strategy. MXene “bricks” bonded by CNF “mortars” of the nacre‐like cell walls induce high mechanical strength, electrical conductivity, and interfacial polarization, yielding the resultant MXene/CNF aerogels an ultrahigh EMI shielding performance. The EMI shielding effectiveness (SE) of the aerogels reaches 74.6 or 35.5 dB at a density of merely 8.0 or 1.5 mg cm–3, respectively. The normalized surface specific SE is up to 189 400 dB cm2 g–1, significantly exceeding that of other EMI shielding materials reported so far.

Abstract Owing to their high robustness and conductivity, 2D transition metal carbides and nitrides known as MXenes are considered as a promising material class for electrochemical catalysis, energy conversion, and storage applications. Nevertheless, conventional hazardous fluoride‐based synthesis routes and the intense intralayer bonding restrict the development of MXenes. Herein, a fluoride‐free, facile, and rapid method for synthesizing self‐assembled 1D architecture from an MXene‐based compound is reported. The MXene nanowire (NW) not only provides a robust connection to the flexible substrate but also effectively increases the electrochemically active surface area. The kinetics‐favorable structure yields a boosted performance for the hydrogen/oxygen evolution reaction and the intake of the zinc ion. The 1D NW based on MXene compound maintains high stability in a quite low overpotential of 236 mV for 24 h without detachment from the substrate and manifests an exceptional high‐power density of 420 W kg−1 over 150 cycles as a flexible aqueous zinc ion battery. This work paves a novel and non‐toxic synthesis method for the 1D nanofiber structure from MXene composition and demonstrates its multifunctional applications for energy conversion and storage.

Abstract Since their discovery in 2011, transition metal carbides or nitrides (MXenes) have attracted a wide range of attention due to their unique properties and promise for use in a variety of applications. However, the low accessible surface area and poor processability of MXene nanosheets caused by their restacking have severely hindered their practical use, and this is expected to be solved by integrating them into macroscopic assemblies. Here, recent progress in the construction of MXene assemblies from 2D to 3D at the macro and/or microlevel is summarized. The mechanisms of their assembly are also discussed to better understand the relationship between performance and assembled structure. The possible uses of MXene assemblies in energy conversion and storage, electromagnetic interference shielding and absorption, and other applications are summarized.

Abstract The residual of malignant tumor cells and lack of bone‐tissue integration are the two critical concerns of bone‐tumor recurrence and surgical failure. In this work, the rational integration of 2D Ti3C2 MXene is reported with 3D‐printing bioactive glass (BG) scaffolds for achieving concurrent bone‐tumor killing by photonic hyperthermia and bone‐tissue regeneration by bioactive scaffolds. The designed composite scaffolds take the unique feature of high photothermal conversion of integrated 2D Ti3C2 MXene for inducing bone‐tumor ablation by near infrared‐triggered photothermal hyperthermia, which has achieved the complete tumor eradication on in vivo bone‐tumor xenografts. Importantly, the rational integration of 2D Ti3C2 MXene is demonstrated to efficiently accelerate the in vivo growth of newborn bone tissue of the composite BG scaffolds. The dual functionality of bone‐tumor killing and bone‐tissue regeneration makes these Ti3C2 MXene‐integrated composite scaffolds highly promising for the treatment of bone tumors, which also substantially broadens the biomedical applications of 2D MXenes in tissue engineering, especially on the treatment of bone tumors.

Abstract 2D transition metal carbides and nitrides called “MXene” are recent exciting additions to the 2D nanomaterials family. The high electrical conductivity, specific capacitance, and hydrophilic nature of MXenes rival many other 2D nanosheets and have made MXenes excellent candidates for diverse applications including energy storage, electromagnetic shielding, water purification, and photocatalysis. However, MXene nanosheets degrade relatively quickly in the presence of water and oxygen, imposing great processing challenges for various applications. Here, a facile solvent exchange (SE) processing route is introduced to produce nonoxidized and highly delaminated Ti3C2Tx MXene dispersions. A wide range of organic solvents including methanol, ethanol, isopropanol, butanol, acetone, dimethylformamide, dimethyl sulfoxide, chloroform, dichloromethane, toluene, and n‐hexane is used. Compared to known processing approaches, the SE approach is straightforward, sonication‐free, and highly versatile as multiple solvent transfers can be carried out in sequence to yield MXene in a wide range of solvents. Conductive MXene polymer composite fibers are achieved by using MXene processed via the solvent exchange (SE) approach, while the traditional redispersion approach has proven ineffective for fiber processing. This study offers a new processing route for the development of novel MXene‐based architectures, devices, and applications.

Abstract A recently created class of inorganic 2D materials, MXenes, has become a subject of intensive research. Reducing their dimensionality from 2D to 0D quantum dots (QDs) could result in extremely useful properties and functions. However, this type of research is scarce, and the reported Ti3C2 MXene QDs (MQDs) have only shown blue fluorescence emission. This work demonstrates a facile, high‐output method for preparing bright white emitting Ti3C2 MQDs. The resulting product is two layers thick with a lateral dimension of 13.1 nm. Importantly, the as prepared Ti3C2 MQDs present strong two‐photon white fluorescence. Their fluorescence under high pressure is also investigated and it is found that the white emission is very stable and the pressure makes it possible to change from cool white emission to warm white emission. Hybrid nanocomposites are then fabricated by polymerizing Ti3C2 MQDs in polydimethylsiloxane (PDMS) solution, and the bright white emitting hybrid materials in white light‐emitting diodes are used. This work provides a facile and general approach to modulate various nanoscale MXene materials, and could further aid the wide development of applications for MXene materials in various optical‐related fields.

Abstract TiO2 is an ideal photocatalyst candidate except for its large bandgap and fast charge recombination. A novel laminated junction composed of defect‐controlled and sulfur‐doped TiO2 with carbon substrate (LDC‐S‐TiO2/C) is synthesized using the 2D transition metal carbides (MXenes) as a template to enhance light absorption and improve charge separation. The prepared LDC‐S‐TiO2/C catalyst delivers a high photocatalytic H2 evolution rate of 333 µmol g−1 h−1 with a high apparent quantum yield of 7.36% at 400 nm and it is also active even at 600 nm, resulting into a 48 time activity compared with L‐TiO2/C under visible light irradiation. Further theoretical modeling calculation indicates that such novel approach also reduces activation energy of hydrogen production apart from broadening the absorption wavelength, facilitating charge separation, and creating a large surface area substrate. This synergic effect can also be applied to other photocatalysts' modification. The study provides a novel approach for synthesis defective metal oxides based hybrids and broaden the applications of MXene family.