Two-dimensional Layer Structure Research Articles

Unveiling the Structural Effects in Hybrid Copper Phosphonate Frameworks for Selective Electrocatalytic CO2 Reduction Reaction.

Electrochemical CO2 reduction holds tremendous promise for transforming carbon dioxide into several value-added energy feedstocks and utilizing renewable energy sources. Herein, we have developed two novel copper-based organophosphonates for selective electrocatalytic conversion of CO2 to CH3OH conversion. The two-dimensional layer structure of Cu3[(Hhedp)2(C4H4N2)].2H2O (I) and the three-dimensional Cu3[(H3hedp)2(C4H4N2)4(SO4)].2H2O (II) have been isolated as single crystals via a hydrothermal strategy. Compound I consists of Cu2+ oxidation states exclusively, while compound II has Cu1+ oxidation states in a network wherein a Cu2+-phosphonate template is embedded inside the framework. Depending on mixed valent oxidation states, compound II exhibits high selectivity compared to compound I for the electrocatalytic reduction of CO2 to CH3OH (C1) as the primary product and CH3COOH (C2) as the secondary product. Notably, product selectivity is enhanced as the Faradaic efficiency (FE) of the competing hydrogen evolution reaction (HER) is significantly reduced in compound II relative to that of I, particularly at higher applied reduction potentials. The optimal ratio of Cu1+ active sites in compound II plays a pivotal role in enhancing methanol selectivity, stabilizing critical intermediates, and maintaining ideal reduction potentials as a noble-metal free electrocatalyst. Moreover, the optical band gap and the Mott-Schottky measurements further suggest the title Cu-phosphonate materials could be promising and effective photocatalysts.

Insight into the mechanism of Zr-Fe bimetallic CUGB-SOFs activating persulfate to degrade tetracycline in water

Tetracycline (TC), as a typical representative of antibiotic pollutants, persists in surface water and wastewater, and there is an urgent need to develop new treatment technologies to address this issue. Supramolecular organic frameworks (SOFs) can activate peroxymonosulfate (PMS) to oxidize TC, but they often suffer from poor activity and hydrostability. To address these issues, this study innovatively introduced 4,4′,4″-[(1,3,5-triazine-2,4,6-triyl) tris(azanediyl)] tribenzoic acid (H3TATAB) as a ligand to synthesize functionalized Zr based CUGB-SOFs. The morphology and structure of the CUGB-SOFs were characterized, revealing that adjacent H3TATAB molecules are interconnected through double hydrogen bonds, intertwine, and entangle with each other, ultimately forming an extremely complex two-dimensional wavy layered structure. Doped by multi-metal (Co, Cu, Fe), the CUGB-SOFs can effectively and consistently activate peroxymonosulfate (PMS) to generate abundant singlet oxygen (1O2) for the degradation of TC. Especially after cycles of experiments, CUGB-SOF-Fe still maintained TC degradation efficiency as high as 84.49%, which breaks through the understanding of traditional hydrogen bond structure. It is believed that Zr dominates the aqueous stable, allowing CUGB-SOF-Fe to act as an electron shuttle, promoting PMS activation and thereby accelerating TC degradation. Finally, combined with the identification of key reactive oxygen species and the analysis of intermediate products by mass spectrometry, the degradation reaction mechanism of TC was proposed.

Multilayer structured bismuth silicate inverse opal film with improved piezo-photocatalytic performance for wastewater purification and dyes removal

Suppressing the recombination of photogenerated charge carriers is thought to be possible by combining the photocatalytic method with the piezoelectric action of piezoelectric semiconductors. A new piezo-photocatalyst, Bi2SiO5 inverse opal film, was prepared by inverse template method. The introduction of 3D ordered inverse opal structure was favorable for light harvesting. The unique two-dimensional layered structure of Bi2SiO5 facilitates electron-hole (e--h+) pair separation. The degradation efficiency of Bi2SiO5 inverse opal film is 15 times higher than that of planar- Bi2SiO5 film under UV light alone. When co-excited by UV light and mechanical energy (ultrasonic vibration), the Bi2SiO5 inverse opal film demonstrated a significantly accelerated degradation rate of RhB compared with planar Bi2SiO5 film. The enhanced piezo-photocatalytic efficiency resulted from the effective separation of photogenerated electron-hole pairs in the Bi2SiO5 inverse opal under the inherent piezoelectric field. Consequently, our work offers fresh perspective on piezo-photocatalytic materials based on Bi2SiO5 for effective wastewater treatment.

Construction of cellulose 3D network composite membrane supported by hydroxylated boron nitride with high surface charge density to achieve high-efficiency osmotic energy harvesting

Ion selectivity and mechanical persistence are critical properties of membranes to harvest osmotic energy. Two-dimensional nanofluidic membranes have been studied to enhance those properties, whereas they are usually constrained due to unsatisfactory mass transfer performances. Herein, a ternary three-dimensional membrane (T-CNF/PVDF/BN-OH composite membrane, abbreviated as CPBN) with distinct mechanical strength and high surface charge density (−2.65 mC·m−2) for sustainable osmotic energy harvesting is designed. In CPBN, negatively charged TEMPO-oxidized cellulose acts as a scaffold and constructs a 3D network structure together with the hydroxylated boron nitride (BN-OH) via a self-assembly process. The affluent nano-constrained ion channels effectively enhance the controllability and effectiveness of ion transport. The abundant ionized carboxyl groups extremely facilitate the selective transportation of the cations, while the BN-OH also assist this process, promoting the one-way transmission of cations in the channel. Additionally, the participation of PVDF polymer forms a network interlock structure, which significantly improves mechanical performances and stability in water. The membrane demonstrates a high power density (10.6 W/m2), measured in minimal testing areas, and an average power density around 1 W/m2 in larger areas, with an energy conversion efficiency of up to 30.7 %. This study provides a promising exploration of replacing traditional two-dimensional layered structure with three-dimensional network structure of cellulose for osmotic energy harvesting.

Synergistic effects of MXene and Co3O4 in composite electrodes: High-performance energy storage solutions

The development of high-performance electrode materials is crucial for advancing supercapacitor technology. The two-dimensional layered structure of MXene (Ti3C2Tx) presents high conductivity, abundant surface functional groups and accessible ion interaction between layers. However, the MXene suffers from the layer aggregation. To overcome this issue, we synthesized a composite material combining MXene with cobalt oxide (Co3O4) to enhance electrochemical performance in supercapacitors. MXene’s two-dimensional layered structure, high conductivity, and abundant surface functional groups allow for efficient ion intercalation, while Co3O4 contributes high theoretical capacitance and rich oxidation states. The resulted MXene/Co3O4 composite exhibits an impressive areal capacitance of 6.456F/cm2 at a current density of 3 mA/cm2, maintaining 90.52 % capacitance retention at 30 mA/cm2, and 81.37 % capacity after 5000 charge–discharge cycles. Additionally, the asymmetric supercapacitor (ASC) device fabricated using the MXene/Co3O4 composite achieves a power density of 6.41 mW/cm2 at an energy density of 0.37 mWh/cm2, with 82.3 % capacitance retention after 5000 cycles. These results demonstrate that the MXene/Co3O4 composite material is a promising candidate for high-performance supercapacitors, offering significant improvements in rate capability and long-term cycling stability.

Disentangling the Optoelectronic Behavior of Lead Iodide Governed by Two-Dimensional Electron Confinement.

We present a joint experimental and theoretical study for complete spectroscopic characterization and optoelectronic properties of lead iodide. Experimentally, we combine X-ray diffraction experiments to elucidate the structure with photoelectron spectroscopy to explore its electronic structure. Computationally, simulations are performed in the frame of density functional theory. We show that PbI2 presents a two-dimensional layered structure and exhibits a large transient photocurrent effect under visible light illumination, which are compatible with the surface photovoltage scenario. The transient photocurrent has an extremely long lifetime: when the sample is lightened with visible light, it shows very long relaxation times and, consequently, huge charge carrier diffusion lengths. We explain this anomalous behavior with the slow carrier mobility of holes and electrons caused by the 2D electron confinement in the layered material. Our results can be used as a simple model for understanding the optoelectronic properties of more complex 2D hybrid perovskites.

Rational fabrication of two polyoxovanadate-based frameworks for efficient detoxifying mustard gas simulant

Two polyoxovanadates (POVs)-based cobalt–organic frameworks, namely [H2Co2(p-bix)4][V8O23] (1) and [Co(o-bix)][V2O6] (2) (where p-bix = 1,4-bis(imidazol-1-ylmethyl)benzene and o-bix = 1,2-bis(imidazol-1-ylmethyl)benzene), were synthesized via a hydrothermal process and thoroughly characterized structurally. Compound 1 features a three-dimensional framework where the inorganic layers {V8Co2}, containing circular [V4O12]4− ({V4}) dimers, are interconnected by p-bix ligands. While compound 2 forms a two-dimensional layer structure where the inorganic {V4} clusters are linked by four binuclear [Co2O3(o-bix)2]2− units through the sharing of O atoms from {V4} clusters. Given the catalytic prowess of POVs in oxidizing various organic substrates, we evaluated the catalytic performance of these two compounds as heterogeneous catalysts for detoxifying mustard gas simulant CEES (2-chloroethyl ethyl sulfide) into the non-toxic CEESO (2-chloroethyl ethyl sulfoxide). The catalytic tests revealed that both compounds effectively catalyze the oxidation of CEES, yielding solely CEESO. Particularly, catalyst 2 exhibited excellent catalytic properties, achieving nearly 100 % conversion and selectivity within just 40 min at room temperature. The prominent performance of 2 remains consistent through at least five recycling cycles, showcasing its durability and effectiveness. This exceptional performance of 2 was achieved due to the synergistic interaction between V and coordinatively unsaturated Co sites within the structure, as confirmed by detailed comparative studies of structure and catalytic activity as well as density functional theory (DFT) calculations.

Strategy of Constructing Ratio-Dependent Coordination Polymer probes and Their Film Application with a Smart Phone for Detection of Lomefloxacin Hydrochloride and Sodium Salicylate.

Lomefloxacin hydrochloride (LMFX) and sodium salicylate (SS) are important targets for real-time detection due to their widespread uses in daily life; accurate and portable monitoring of LMFX and SS is crucial for human health concerns accordingly. Developing a precise and smart platform for determination of the above analytes remains a significant challenge. Herein, a high-sensitivity platform incorporating a luminescence electrospinning film, self-designed smart-phone app, and portable 3D printing device has been developed to identify LMFX and SS. In this work, two heterometallic coordination polymers with two-dimensional layer structures have been synthesized based on 2,2'-oxidiacetic acid ligand (H2oda), namely, [LnPb(oda)2(CH3COO)]n [Ln = Eu (IMU-1); Tb (IMU-2)]. IMU-1 and IMU-2 were ratio-dependent luminescence probes, which could selectively and sensitively sense with LMFX and SS, respectively. Additionally, the synthesized electrospinning films incorporating IMU-1 and IMU-2 were employed to identify LMFX and SS. Both films could rapidly photograph and color-capture through a portable 3D printing device, along with a self-designed smart-phone app that enabled convenient and quick determination of the concentrations of the above analytes. Remarkably, the mechanism exploration indicated that electron transfer from ligands to analytes affected the antenna effect and further utilized the intrinsic luminescence of analytes along with the luminescence quenching of Ln3+ ions. Furthermore, a strategy for constructing ratio-based fluorescent probes by exploiting the luminescence of analytes and Ln3+ ions in host coordination polymers is proposed. This work provides a new insight by combining luminescence probes, portable devices, and a smart-phone app for real-time detection of drugs and food additives.

A sulfur-containing Cd(II) coordination polymer assembled from 4-(4-pyridinyl)thiazole-2-thiol: synthesis, crystal structure, properties, and Hirshfeld surface analysis

The 4-(4-pyridinyl)thiazole-2-thiol (HPTT) molecule with biological activities is a sulfur-containing organic ligand. Here, one new sulfur-containing coordination polymer based on HPTT and potassium thiocyanate (KSCN), namely, {[Cd(PTT)(HPTT)(SCN)}n, has been synthesized and characterized by physicochemical methods. The single-crystal X-ray diffraction analyses reveal the compound crystallizes in a monoclinic P21/n space group and features a one-dimensional line structure. The crystal structure is stabilized through intramolecular C–H···N and C–H···S hydrogen bonds and intermolecular N–H···N, C–H···π, and π⋯π interactions, generating a two-dimensional supramolecular layer structure. The interactions are also analyzed using Hirshfeld surface analysis. Moreover, the compound shows a relatively thermal stability and solid-state photoluminescence at room temperature. One new sulfur-containing coordination polymer based on 4-(4-pyridinyl)thiazole-2-thiol and potassium thiocyanate has been synthesized and characterized. The single-crystal X-ray diffraction analyses reveal the compound crystallizes in a monoclinic P21/n space group and features a one-dimensional line structure. The crystal structure is stabilized by hydrogen bonds and π⋅⋅⋅π stacking interactions, generating a two-dimensional supramolecular layer structure. The interactions are also analyzed using Hirshfeld surface analysis.

Effect of synergistic CeO2/MoS2 abrasives on surface roughness and material removal rate of quartz glass

Cerium oxide (CeO2) is a primary abrasive frequently used in quartz glass polishing slurry for facilitating glass surface planarisation. However, due to its exorbitant synthesis costs and extremely corrosive as well as toxic reagents in the system, the chemical modification of CeO2 abrasives have limited practical applications. In this work, a novel chemical mechanical polishing slurry for quartz glass incorporating potassium oleate (KOL), deionised water (DIW), cerium dioxide and molybdenum disulphide (MoS2) was developed in this paper to enhance the chemical mechanical polishing (CMP) performance of CeO2-based polishing slurry. KOL creates an alkaline environment for the system, further develops silicate insoluble substances on the quartz glass surface and boosts the material removal rate (MRR) in CMP. MoS2 exhibits a two-dimensional layered nanosheet structure between the abrasive and quartz glass, and then acts as a solid lubricant to prevent excessive mechanical damage, thus increasing the abrasive's wettability. This characteristic helps avoid scratches and other defects on the quartz glass surface. Notably, when the content of KOL and MoS2 in the system is 0.2 wt% and 0.3 wt%, respectively, the surface roughness of the quartz glass surface is 0.48 nm under the scanning area of 15 × 15 μm2 and the MRR is 24.03 μm/h following CMP. The synergistic interaction between CeO2 and MoS2 significantly enhances the abrasive performance on the glass substrate, offering a novel approach for developing polishing fluids that leverage the collaborative effects between abrasives and two-dimensional materials.

A Strongly Reducing sp2 Carbon-Conjugated Covalent Organic Framework Formed by N-Heterocyclic Carbene Dimerization.

Covalent organic frameworks linked by carbon-carbon double bonds (C=C COFs) are an emerging class of crystalline, porous, and conjugated polymeric materials with potential applications in organic electronics, photocatalysis, and energy storage. Despite the rapidly growing interest in sp2 carbon-conjugated COFs, only a small number of closely related condensation reactions have been successfully employed for their synthesis to date. Herein, we report the first example of a C=C COF, CORN-COF-1 (CORN = Cornell University), prepared by N-heterocyclic carbene (NHC) dimerization. In-depth characterization reveals that CORN-COF-1 possesses a two-dimensional layered structure and hexagonal guest-accessible pores decorated with a high density of strongly reducing tetraazafulvalene linkages. Exposure of CORN-COF-1 to tetracyanoethylene (TCNE, E1/2 = 0.13 V and -0.87 V vs. SCE) oxidizes the COF and encapsulates the radical anion TCNE•- and the dianion TCNE2- as guest molecules, as confirmed by spectroscopic and magnetic analysis. Notably, the reactive TCNE•- radical anion, which generally dimerizes in the solid state, is uniquely stabilized within the pores of CORN-COF-1. Overall, our findings broaden the toolbox of reactions available for the synthesis of redox-active C=C COFs, paving the way for the design of novel materials.

Synthesis and recent developments of MXene-based composites for photocatalytic hydrogen production

Abstract The energy crisis has already seriously affected the daily lives of people around the world. As a result, designing efficient catalysts for photocatalytic hydrogen evolution (PHE) is a promising strategy for energy supply. Co-catalyst modification can significantly enhance the photocatalytic activity of single semiconductors, overcoming limitations posed by their narrow visible light absorption range and high electron–hole recombination rate. MXene-based composites demonstrate immense potential as co-catalysts for photocatalytic hydrogen production owing to their distinctive two-dimensional layered structure and outstanding photoelectrochemical properties, and further research and development efforts surrounding MXene-based composites will contribute significantly to the progress of sustainable energy technologies. In this review, we offer a comprehensive overview of synthesis methods for MXene and MXene-based composites, highlight illustrative instances of binary and ternary MXene-based composites in PHE, and explore potential avenues for future research and expansion of MXene-based composites.

Hazardous CO, NO, NH3 gases over boron and beryllium doped α-CN monolayers: A first principles study for sensing and removal applications

The exploration of two-dimensional (2D) honeycomb layered structure (HLS) has garnered significant attention due to their multifunctional properties, with diverse applications emerging in various fields. Motivated by the challenges posed by hazardous gases such as CO, NO, NH3 and inspired by the unique properties of 2D HLS this first principles study digs into the structural, electronic, and sensing properties of Boron and Beryllium doped α-CN monolayers. Rendering the structural and electronic variations induced by B and Be doping, our analysis reveals distinct functionalities for α-CN monolayers. Boron doping at the C-site exhibits promise for NO and NH3 sensing (with 73 % and 77 % increment in adsorption energies), while B-doping at the N-site enhances suitability for gas removal applications. Similarly, Be doping demonstrates effectiveness in gas removal across both C and N sites. Notably, the ultra-fast response (2.31 × 10−8 s) observed for NO adsorption over B-doped α-CN highlights its potential as a rapid sensor. Additionally, work function analysis suggests the suitability of B-doped α-CN for φ-type sensing in NH3 adsorption. These findings underscore the applicability of doped α-CN monolayers in gas sensing mechanisms.

Structural stability and metallization of orpiment at high pressure

Binary arsenic sulfide compounds have garnered significant attention owing to their wide-ranging physical properties and promising potential in the domains of electronics and optoelectronics. As a naturally abundant and historically significant semiconductor mineral, orpiment (crystalline As2S3) has encountered limited utilization in the realm of optoelectronics due to its considerable bandgap width. For orpiment with its quasi-two-dimensional layered structure, pressure is one of the most effective methods to regulate its crystal structure and physical properties. In this work, the structural behavior, optical and electrical properties of orpiment under high pressure have been investigated systematically utilizing a combination of experimental methods and theoretical calculations. The monoclinic structure of orpiment is stable up to 48 GPa without structural phase transitions involving changes in the space group occurred. The noticeable changes of lattice parameters, axial ratios, and interatomic distances above 20 GPa are ascribed to a transformation from a two-dimensional layered structure to a quasi-three-dimensional crystal framework. Continuous lattice contraction upon compression is accompanied by gradual bandgap narrowing, which leads to metallization of orpiment. The pressure-induced metallization of orpiment occurs above 40 GPa. The structural behavior, optical and electrical properties of orpiment at high pressure exhibit reversible hysteresis upon pressure release. This study offers a high-pressure approach for modulating crystal structure and physical properties of orpiment to expand its potential applications in the fields of electronics and optoelectronics.

Ultra-thin SnS2 nanosheets grown on carbon nanofibers with high-performance in sodium-ion energy storage

SnS2 with two-dimensional layered structure has great application promising in the energy storage system due to its super high theoretical capacity. However, the serious volume expansion and low intrinsic conductivity are difficult to meet the commercial application of SnS2 in sodium-ion batteries (SIBs). Herein, SnS2/CNF was successfully prepared by simple electrospinning technique and hydrothermal method. Based on the synergistic effect between ultra-thin nanosheets and carbon nanofibers (CNF), the anode material not only shortened the path of electron transport, but also accelerated the sodium ion reaction kinetics, thus showed outstanding stability and reversibility SIBs. The SnS2/CNF displayed the excellent rate properties (352 mAh g-1 at 5 A g-1) as well as stable long term cycle performance (338 mAh g-1 at 3 A g-1 after 500 cycles). Furthermore, the SnS2/CNF//AC sodium-ion hybrid capacitor (SIHCs) exhibits excellent energy density and power density of 97 Wh kg-1/54 W kg-1. The capacity retention is 81 % after 2500 cycles at 1 A g-1. The SIHCs could light up to 100 LEDs easily, which thus exhibited great practical application potential in energy storage device.

Synthesis, crystal structures and fluorescence recognition properties of two novel chiral coordination compounds based on alanine derivate

Two novel chiral coordination compounds {[Cd(D-pmala)(2,2′-bipy)(H2O)]⋅1·25H2O}n (1), {[Pb4(D-pmala)4(5,5′-DM-2,2′-bipy)4(H2O)2]⋅7H2O}n (2) (D-pmala = N-(4-carboxyl) benzoyl-d-alanine, 2,2′-bipy = 2,2′-Bipyridine, 5,5′-DM-2,2′-bipy = 5,5′-Dimethyl-2,2′- Bipyridine) have been successfully synthesized under hydrothermal conditions. Their structures were identified using single-crystal X-ray crystallography and characterized by infrared spectroscopy, elemental analysis, thermogravimetric analysis, powder X-ray diffraction and solid-state circular dichroism spectra. Crystallographic analysis indicate that compound 1 features a "Z"-shaped one-dimensional chain structure, which further extends into three-dimensional supramolecular architectures through hydrogen-bonding interactions. Compound 2 displays a two-dimensional layer structure, a two-dimensional double-layer network structures is further formed through the hydrogen-bonding interactions. Moreover, The fluorescence recognition properties of compound 1 indicate that it is highly selective in detecting Cu2+ ions and tyrosine (Tyr) enantiomers in aqueous solutions, which indicates that compound 1 can be expected to be a bifunctional fluorescent recognition sensor to detect metal ions and amino acid enantiomers.

Structural phase transition and potential superconductivity initiated by pressure-driven in 1T–CrSe2

The exploration of the superconducting properties of antiferromagnetic parent compounds containing transition metals under pressure provides a unique idea for finding and designing superconducting materials with better performance. In this paper, the close relationship between the possible superconductivity and structure phase transition of the typical van der Waals layered material 1 T–CrSe2 induced by pressure is studied by means of electrical transport and x-ray diffraction for the first time. We introduce the possibility of pressure-induced superconductivity at 20 GPa, with a critical T c of approximately at 4 K. The superconductivity persists up to the highest measured pressure of 70 GPa, with a maximum T c ∼ 5 K at 24 GPa. We observed a structure phase transition from P-3 m1 to C2/m space group in the range of 9.4–11.7 GPa. The results show that the structural phase transition leads to the metallization of 1 T–CrSe2 and the further pressure effect makes the superconductivity appear in the new structure. The material undergoes a transition from a two-dimensional layered structure to a three-dimensional structure under pressure. This is the first time that possible superconductivity has been observed in 1 T–CrSe2.

Zn, Cd and Cu Coordination Polymers for Metronidazole Sensing and for Ullmann and Chan-Lam Coupling Reactions.

Five compounds, [Zn2(bpe)(BPTA)2(H2O)2] ⋅ 2H2O (1); [Zn(bpe)(BPTA)] (2); [Cd(bpe)(BPTA)H2O] (3); [Cd(BPTA) (bpmh)] ⋅ 2H2O (4); and Cu2(BPTA)2(bpmh)3(H2O)2] ⋅ 2H2O (5) were prepared employing 2,5-bis(prop-2-yn-1-yloxy)terephthalic acid (2, 5 BPTA) as the primary ligand and 1,2-di(pyridin-4-yl)ethane (4, 4' bpe) (1-3) and 1,2-bis(pyridin-3-ylmethylene)hydrazine (bpmh) (4-5) as the secondary ligands. Single crystal studies indicated that the compounds 1, 3 and 5 have two-dimensional layer structures and compounds 2 and 4 three-dimensional structures. The luminescence behaviour of the compounds 2 and 3 were explored for the sensing of metronidazole in aqueous medium. The studies indicated that the compounds can detect metronidazole in ppm level both in solution as well as simple paper strips. The Cu compound 5 was found to lose the coordinated water molecule at 100 °C without any structural change. The coordinatively unsaturated Cu-centre were examined towards the Lewis acidic character by carrying out the Ullmann type C-C homocoupling reaction of the aromatic halide compounds. The compounds, 4 and 5, also have the Lewis basic functionality arising out the =N-N=, aza groups. The bifunctional nature of the coordination polymers (CP) was explored towards the Chan-Lam coupling reaction between phenyl boronic acid and aniline derivatives in the ethanol medium. In both the catalytic reactions, good yields and recyclability were observed. The present studies illustrated the rich diversity that the transition metal containing compounds exhibit in extended framework structures.

Research Progress on Ammonia Sensors Based on Ti3C2Tx MXene at Room Temperature: A Review.

Ammonia (NH3) potentially harms human health, the ecosystem, industrial and agricultural production, and other fields. Therefore, the detection of NH3 has broad prospects and important significance. Ti3C2Tx is a common MXene material that is great for detecting NH3 at room temperature because it has a two-dimensional layered structure, a large specific surface area, is easy to functionalize on the surface, is sensitive to gases at room temperature, and is very selective for NH3. This review provides a detailed description of the preparation process as well as recent advances in the development of gas-sensing materials based on Ti3C2Tx MXene for room-temperature NH3 detection. It also analyzes the advantages and disadvantages of various preparation and synthesis methods for Ti3C2Tx MXene's performance. Since the gas-sensitive performance of pure Ti3C2Tx MXene regarding NH3 can be further improved, this review discusses additional composite materials, including metal oxides, conductive polymers, and two-dimensional materials that can be used to improve the sensitivity of pure Ti3C2Tx MXene to NH3. Furthermore, the present state of research on the NH3 sensitivity mechanism of Ti3C2Tx MXene-based sensors is summarized in this study. Finally, this paper analyzes the challenges and future prospects of Ti3C2Tx MXene-based gas-sensitive materials for room-temperature NH3 detection.

Metal-induced assembly of two novel MOFs: Sensitive fluorescence sensing properties and insights into mechanisms

Two new MOFs, namely, [Pb2(2-CPP)2(H2N-bpdc)]n (1) and [Cd(3-CPP)2]n (2), have been prepared by using N- and O-donor ligands and metal ions Pb2+, Cd2+ under hydrothermal conditions. The single-crystal X-ray diffraction analysis was used to measure the crystal structure. The complex 1 is one-dimensional chain structures, and it can further form two-dimensional and three-dimensional supramolecular structures through π-π stacking. The complex 2 is a two-dimensional layered structure, which can form three-dimensional supramolecular structure through π-π interaction. The synthesized MOFs exhibit ligand-based luminescence, which can be attributed to the coordination effect. Due to its excellent fluorescence properties, complex 2 can be used for selective and sensitive detection of nitro aromatic compounds (NAC) and metal ions. The results show that the complex 2 could quickly detect Cr2O72−, nitrobenzene and Fe3+by fluorescence quenching, and had good anti-interference and cycle stability, so it was a potential chemical fluorescence sensing material. The identification mechanism of 2 is discussed by electron transfer analysis method and density functional theory (DFT) calculation.