CH4 Molecules Research Articles

Recent Advances in Perovskite Nanomaterials for Sensing Applications

Abstract Perovskite-structured materials have been extensively studied for sensing applications on account of their good thermal stability and 3-4 eV bandgap. They have been utilized to detect traces of O2, NO, CO, NO2, CO2, H2O, CH4, H2 and similar smaller gas molecules such as C2H5OH etc. In addition, other sensing applications are optical sensing, I-V fluctuations, strain sensors, electromechanical sensors, sensing of metal ions, etc. Perovskite-structured halides are reported for sensing of metal ions, toxic gases, Volatile Organic Compounds (VOCs), detection of fungicides, pesticides, explosives, cellular imaging, radiation detection and humidity and temperature sensing.

Methane Gas Transport in Ca-MMT Shale Nanoslits Considering Water Content Effects: Insights from Molecular Dynamics Simulations.

Two-phase flow remains a significant challenge in the development of water-bearing shale gas, particularly regarding the flow of gases through clay minerals in such formations. Nonequilibrium molecular dynamics simulation is investigated to research the two-phase flow of water (H2O) and methane (CH4) through Ca-montmorillonite (MMT) shale nanoslits. The results indicate that water molecules preferentially adsorb onto the surfaces of the Ca-MMT shale nanoslits, leading to the formation of water bridges within the nanoslits as water content increases. Notably, CH4 molecules exhibit complete solubility in the water phase, and their maximum velocity gradually decreases, resulting in a flattened parabolic flow profile with a higher gas-water percent (GWP). In the two-phase flow, CH4 continues to flow without slip in the inorganic nanopores due to water molecules occupying the surfaces and creating a water film. However, when the water content (GWP) exceeds 80.87%, CH4 gas molecules become dissolved in the water, filling the inorganic nanoslits and leading to a zero-gas flux. This condition causes CH4 retention in adjacent nanoslits, creating a "water lock gas" effect. This research provides a theoretical foundation for understanding multiphase flow in water-bearing shale gas and offers a refined description of the shale gas extraction process for future application.

A Grafting Hydrogen‐bonded Organic Framework for Benchmark Selectivity of C2H2/CO2 Separation under Ambient Conditions

AbstractReticular chemistry and pore engineering have garnered significant advancements in metal–organic frameworks and covalent organic frameworks, leveraging robust metal‐coordination and covalent bonds. However, these achievements remain elusive in hydrogen‐bonded organic frameworks, hindered by their inherent weakness in hydrogen bonding. Herein, we strategically manipulate the porosity of hydrogen‐bonded frameworks through a grafting approach, culminating in the synthesis of two isomorphic HOFs, HOF‐FJU‐99 and HOF‐FJU‐100, with distinct pore environments. Remarkably, HOF‐FJU‐100, with its microporous architecture, not only showcases exceptional stability but also achieves unparalleled separation efficiency and ultrahigh selectivity for C2H2/CO2 mixtures (50/50, v/v) under ambient conditions. Its IAST selectivity value of 201 stands as a benchmark, towering over all previously reported HOFs. The pore of HOF‐FJU‐100 boasts an electrostatic potential highly favourable for C2H2 adsorption, as evidenced by single crystal X‐ray diffraction analysis revealing multiple hydrogen bonding interactions between C2H2 molecules and the framework. In situ gas‐carrier powder X‐ray diffraction analysis underscores the adaptability of pore structure, dynamically adjusting its orientation in response to C2H2, thereby enabling a highly efficient and specific separation of C2H2/CO2 mixtures through specific adsorptive interactions.

Simulation Study on Diffusion and Local Structure of CH4, CO2, SO2, and H2O Mixtures into Double-Layers Graphene.

Graphene has been widely studied as an ideal material for the adsorption and separation. In this work, we used molecular dynamics simulations to investigate the evolution of diffusion and local structure of CH4, CO2, SO2, and H2O mixtures into double-layers graphene under seven different interlayer spacings and four different CO2 concentrations. The results showed that the adsorption of CH4 and CO2 molecules on the graphene surface weakened with increased interlayer spacing. The diffusion capacities of CH4 and CO2 in the mixed system were significantly improved by increasing the interlayer spacing. In interlayer spacings ranging from 5 to 10 nm, the diffusion capacities of each component varied significantly in the order CH4 > CO2 ≫ H2O > SO2. Compared with CH4 and CO2, the local structures of SO2 and H2O were more affected by the interlayer spacing. Larger interlayer spacings or higher CO2 concentrations were advantageous for the formation of stronger hydrogen bond structures between H2O molecules. When the CO2 concentrations were between 10% and 20% and the interlayer spacing of graphene was 8 nm, the graphene structure exhibited the best adsorption and separation effects on CH4 and other components.

Unraveling the Synergy of Au and Polar MgO(111) Surface in Photothermal Catalytic Oxidative Coupling of Methane

AbstractDirect and selective catalytic oxidative coupling of methane (OCM) into high‐carbon products is a great challenge in C1 chemistry. Herein, the successful fabrication of a series of Au clusters loaded on different MgO facets of (111), (110), and (100) is reported. This work demonstrates the Au‐loaded MgO(111) (denoted as Au/MgO(111)) shows the highest C2H6 yield of 12733.4 µmol g−1 h−1 and selectivity of 90.4%, which is 2.46 times higher than that of Au/MgO(110) (5171.4 µmol g−1 h−1) and 25.14 times higher than that of Au/MgO(100) (506.4 µmol g−1 h−1). Moreover, the high activity of Au/MgO(111) can be well maintained over 100 h. Detailed in situ experiments and theoretical calculation reveal such great performance can be attributed to 1) the strong electronic affinity of the surface oxygen species on polar MgO(111) and CH4with the lowest adsorption energy of −0.82 eV; 2) the Au/MgO(111) shows the lowest ΔERDS of 0.53 eV in the rate‐deterime step of OCM that comes in activating the second CH4 molecule; 3) the Au can act as a hole acceptor under light irradiation and adsorb *CH3 with a strong d‐σ hybridization, resulting in an increased C2H6 selectivity.

Exploration of Zr-doped PtSe2 monolayer for sensing C2H2 and C2H4 in oil-immersed transformers of HVDC converter station: A first-principles investigation

Using the first-principles theory, this work purposes Zr-doped PtSe2 (Zr-PtSe2) monolayer as a potential sensing material upon two typical dissolved gases (C2H2 and C2H4), in order to evaluate the operation status of the oil-immersed transformers. Zr-doping on the pristine PtSe2 monolayer is firstly analyzed, yielding the formation energy of −3.12 eV. The Zr-PtSe2 monolayer conducts chemisorption upon C2H2 and C2H4 with the adsorption energy of −1.40 and −1.02 eV, respectively. The electronic property analysis of the gas adsorbed systems reveal the much higher sensing response upon C2H2 molecule, and the recovery property analysis uncovers the reusability for the purposed material. Moreover, the work function is also analyzed to explore the sensing potential of Zr-PtSe2 monolayer based on its change after gas adsorption. The findings pave the way to explore the PtSe2-based material as gas sensors, providing informative guidance for gas sensing material exploration in the electrical engineering.

Modulating the chemical environment of Ni2+ for the oxidative dehydrogenation of ethane: The formation of LAS(Al3+/Ga3+)-Ni-OH site

The oxidative dehydrogenation of ethane to ethylene (ODHE) usually suffers from the issues of ethane conversion-ethylene selectivity seesaw. Herein, a series of alumina-supported Ni and Ga catalysts with different molar ratios of Ni to Ga were synthesized by facile impregnation method constructing the Lewis acid site (LAS) strategy to obtain great ethylene selectivity (97 %). The variation of Ni:Ga ratio adjusted the ionic substitution ability, redox ability and acidity, thus regulate the chemical environment of Ni2+ to the formation of LAS(Al3+/Ga3+)-Ni-OH structure, which was proposed to be the active site for selective oxidation of ethane to ethylene, as proved by H2-TPR, ToF-SIMS, quasi in-situ XPS and in-situ FTIR. Moreover, the probable mechanism of ODHE reaction was proposed that C2H6 molecules were mainly adsorbed on LAS sites and activated on Ni-OH site of the catalyst. The pulse test further suggested that O- was mainly associated with the generation of CO2 and Ni(2-n)+ was connected with the production of CH4. It is highlighted that adjusting the Ni-related species and oxygen species on the catalyst surface are crucial to further improve the ethylene selectivity.

A Stable Layered Microporous MOF Assembled with Y-O Chains for Separation of MTO Products.

Benefiting from highly tunable pore environments, some metal-organic frameworks (MOFs) have recently shown promising prospects in the separation of methanol-to-olefin (MTO) products (mainly C3H6 and C2H4). However, the "trade-off" between gas storage capacity and selectivity always results in inefficient separation. In addition, poor stability of MOFs also limits practical separation applications. Herein, we have successfully assembled a layered Y-MOF (FJI-W9) with bent diisophthalate ligands (H4L), Y-O chains, and 2-fluorobenzoic acids. As expected, FJI-W9 not only exhibits good chemical stability but also shows significant potential for C3H6/C2H4 separation. For FJI-W9, the C3H6 uptake at 298 K and 10 kPa is 63 cm3/g, and the IAST selectivity of FJI-W9 for C3H6/C2H4 (V/V = 50/50) is calculated to be 20.5. To the best of our knowledge, both C3H6 uptake and selectivity of FJI-W9 surpass most porous materials. GCMC simulation indicates that the special supramolecular binding sites in FJI-W9 have much stronger interactions with C3H6 than C2H4 molecules. More importantly, practical breakthrough experiments demonstrate that FJI-W9 can effectively separate C3H6/C2H4 (50/50) mixtures, thus obtaining high-purity C2H4 and C3H6, respectively.

A qubit-efficient variational selected configuration-interaction method

Abstract Finding the ground-state energy of molecules is an important and challenging computational problem for which quantum computing can potentially find efficient solutions. The variational quantum eigensolver (VQE) is a quantum algorithm that tackles the molecular groundstate problem and is regarded as one of the flagships of quantum computing. Yet, to date, only very small molecules were computed via VQE, due to high noise levels in current quantum devices. Here we present an alternative variational quantum scheme that requires significantly less qubits than VQE. The reduction in the qubit number allows for shallower circuits to be sufficient, rendering the method more resistant to noise. The proposed algorithm, termed variational quantum selected-configuration-interaction (VQ-SCI), is based on: (a) representing the target groundstate as a superposition of Slater determinant configurations, encoded directly upon the quantum computational basis states; and (b) selecting a-priory only the most dominant configurations. This is demonstrated through a set of groundstate calculations of the H2, LiH, BeH2, H2O, NH3 and C2H4 molecules in the sto-3g basis set, performed on IBM quantum devices. We show that the VQ-SCI reaches the full configuration interaction energy within chemical accuracy using the lowest number of qubits reported to date. Moreover, when the SCI matrix is generated ‘on the fly’, the VQ-SCI requires exponentially less memory than classical SCI methods. This offers a potential remedy to a severe memory bottleneck problem in classical SCI calculations. Finally, the proposed scheme is general and can be straightforwardly applied for finding the groundstate of any Hermitian matrix, outside the chemical context.

AlN Nanotube Decorated with Small Tin Oxide Clusters as a Novel CH4 Sensing Material.

The success of carbon nanotubes has triggered a great deal of research interest in other one-dimensional nanomaterials with the aim of designing innovative nanostructures with attractive and distinctive attributes for applications in sensing gas molecules and toxic substances. In the present study, first-principles density functional theory calculations were exploited to assess the capability of the small tin oxide cluster (SnxOy)-decorated (6,0)aluminum nitride (AlN) nanotube for detecting methane(CH4) in terms of energetic, structural, and electronic properties. We found that SnxOy clusters were chemisorbed on the surface of the AlN nanotube due to the considerable adsorption energy and the notable charge transfer from the former to the latter. Further calculations demonstrate that the energy band gap and work function of the AlN nanotube were reduced in the presence of additives. Benefiting from the higher affinity of SnxOy toward the CH4 molecule, the Sn3O3-decorated AlN nanotube exhibited the greatest CH4 adsorption energy. The electrical conductivity increased as the energy band gap and effective mass decreased dramatically. Additionally, the type of Sn3O3-decorated AlN nanotube changed from a p-type semiconductor to an n-type one after adsorbing the CH4 molecule. Therefore, the Sn3O3-decorated AlN nanotube endows great promise as a thermopower-based, resistance-based, and Seebeck-effect-based CH4 sensing material.

Growth Kinetics of Graphene on Cu(111) Foils from Methane, Ethyne, Ethylene, and Ethane

AbstractChemical vapor deposition of carbon precursors on Cu‐based substrates at temperatures exceeding 1000 °C is currently a typical route for the scalable synthesis of large‐area high‐quality single‐layer graphene (SLG) films. Using molecules with higher activities than CH4 may afford lower growth temperatures that might yield fold‐ and wrinkle‐free graphene. The kinetics of growth of graphene using hydrocarbons other than CH4 are of interest to the scientific and industrial communities. We measured the growth rates of graphene islands on Cu(111) foils by using C2H2, C2H4, C2H6 and CH4, respectively (each mixed with H2). From such kinetics data we obtain the activation enthalpy (ΔH≠) of graphene growth as shown in parentheses (C2H2 (0.93±0.09 eV); C2H4 (2.05±0.19 eV); C2H6 (2.50±0.11 eV); CH4 (4.59±0.26 eV)); C2Hy (y=2, 4, 6) show similar growth behavior but CH4 is different. Computational fluid dynamics and density functional theory simulations suggest that C2Hy differs from CH4 due to different values of adsorption energy and the lifetime of relevant carbon precursors on the Cu(111) surface. Combining experimental and simulation results, we find that the rate determining step (RDS) is the dissociation of the first C−H bond of CH4 molecules in the gas phase, while the RDS using C2Hy is the first dehydrogenation of adsorbed C2Hy that happens with assistance of H atoms adsorbed on the Cu(111) surface. By using C2H2 as the carbon precursor, high‐quality single‐crystal adlayer‐free SLG films are achieved on Cu(111) foils at 900 °C.

Growth Kinetics of Graphene on Cu(111) Foils from Methane, Ethyne, Ethylene, and Ethane.

Chemical vapor deposition of carbon precursors on Cu-based substrates at temperatures exceeding 1000 °C is currently a typical route for the scalable synthesis of large-area high-quality single-layer graphene (SLG) films. Using molecules with higher activities than CH4 may afford lower growth temperatures that might yield fold- and wrinkle-free graphene. The kinetics of growth of graphene using hydrocarbons other than CH4 are of interest to the scientific and industrial communities. We measured the growth rates of graphene islands on Cu(111) foils by using C2H2, C2H4, C2H6 and CH4, respectively (each mixed with H2). From such kinetics data we obtain the activation enthalpy (ΔH≠) of graphene growth as shown in parentheses (C2H2 (0.93±0.09 eV); C2H4 (2.05±0.19 eV); C2H6 (2.50±0.11 eV); CH4 (4.59±0.26 eV)); C2Hy (y=2, 4, 6) show similar growth behavior but CH4 is different. Computational fluid dynamics and density functional theory simulations suggest that C2Hy differs from CH4 due to different values of adsorption energy and the lifetime of relevant carbon precursors on the Cu(111) surface. Combining experimental and simulation results, we find that the rate determining step (RDS) is the dissociation of the first C-H bond of CH4 molecules in the gas phase, while the RDS using C2Hy is the first dehydrogenation of adsorbed C2Hy that happens with assistance of H atoms adsorbed on the Cu(111) surface. By using C2H2 as the carbon precursor, high-quality single-crystal adlayer-free SLG films are achieved on Cu(111) foils at 900 °C.

Understanding the Enhanced Separation Mechanism of C2H4/C2H6 at Low Pressure by HKUST−1

The production of ethylene (C2H4) is typically accompanied by the formation of impurities like ethane (C2H6), making the separation of C2H4 and C2H6 crucial in industrial processes. Here, we investigated the S-shaped adsorption phenomenon of C2H6 on the metal–organic framework HKUST−1. The virial equation is used to fit the C2H6 and C2H4 adsorption isotherms under low coverage. The results showed that the repulsion energy between neighboring C2H6 molecules was significantly higher than that between neighboring C2H4 molecules, which was an important reason for the lower adsorption of C2H6 by HKUST−1 at low coverage. As more molecules are adsorbed, gas molecules aggregate within pores, leading to more hydrogen bonds formed between HKUST−1 and larger-sized C2H6 under high coverage conditions. This phenomenon plays a crucial role in the S-shaped adsorption behavior of HKUST−1 on C2H6. Additionally, this unique adsorption behavior allows for the efficient separation of C2H4/C2H6 mixtures at low pressures. The ideal adsorbed solution theory (IAST) selectivity of HKUST−1 for C2H4/C2H6 mixtures was 3.78 at 283 K and 1 bar, but increased significantly to 7.53 under low pressure. This unique mechanism provides a theoretical basis for the low-pressure separation of C2H4/C2H6 by HKUST−1 and establishes a solid foundation for future practical research applications.

Infrared Spectroscopy of CH5+ Cations in Helium Nanodroplets.

The methanium CH5+ is a prototypical fluxional ion whose infrared spectra remain unassigned. Here we report on the infrared spectra of CH5+ cations and its deuterated isotopomer, CH4D+, in helium droplets at a low temperature of 0.38 K. The ions were produced upon protonation of CH4 molecules, a technique that was developed in this work. The spectra of CH5+ around 3000 cm-1 show two strong and broad infrared bands and a weak shoulder, reflecting its highly fluxional nature. The spectrum of CH4D+ shows a much sharper infrared band, indicating a partial quenching of the exchange of H/D atoms. This work also reports on the infrared spectrum of the methane dimer radical cations (CH4)2+.

A Grafting Hydrogen-bonded Organic Framework for Benchmark Selectivity of C2H2/CO2 Separation under Ambient Conditions.

Reticular chemistry and pore engineering have garnered significant advancements in metal-organic frameworks and covalent organic frameworks, leveraging robust metal-coordination and covalent bonds. However, these achievements remain elusive in hydrogen-bonded organic frameworks, hindered by their inherent weakness in hydrogen bonding. Herein, we strategically manipulate the porosity of hydrogen-bonded frameworks through a grafting approach, culminating in the synthesis of two isomorphic HOFs, HOF-FJU-99 and HOF-FJU-100, with distinct pore environments. Remarkably, HOF-FJU-100, with its microporous architecture, not only showcases exceptional stability but also achieves unparalleled separation efficiency and ultrahigh selectivity for C2H2/CO2 mixtures (50/50, v/v) under ambient conditions. Its IAST selectivity value of 201 stands as a benchmark, towering over all previously reported HOFs. The pore of HOF-FJU-100 boasts an electrostatic potential highly favourable for C2H2 adsorption, as evidenced by single crystal X-ray diffraction analysis revealing multiple hydrogen bonding interactions between C2H2 molecules and the framework. In situ gas-carrier powder X-ray diffraction analysis underscores the adaptability of pore structure, dynamically adjusting its orientation in response to C2H2, thereby enabling a highly efficient and specific separation of C2H2/CO2 mixtures through specific adsorptive interactions.

Methane Desorption-Diffusion Behaviors in Micropores of Coal under Different Water Displacement Pressures.

Hydraulic fracturing not only enhances the flow conductivity of coal seams but also transforms the CH4 adsorbed in coal seams into free CH4 and then outputs it via the desorption-diffusion process, thus improving the output quantity and efficiency of CH4. In this paper, taking the coal from Changping mine in Shanxi as the research object, the 3D macromolecule model of coal was established by using analytical test experiments, and the molecular dynamics simulation method of desorption and diffusion was applied to study the characteristics of methane desorption rate and diffusion behaviors under different driving water pressures through the parameters of gas-water concentration distribution, desorption and diffusion rates, and the interaction energies between the coal and the gas-liquid. The results show that the water drive can increase the desorption rate of methane. With the increase of methane adsorption pressure, the desorption effect of water drive becomes stronger and then weaker. The desorption effect of water drive was best when the methane adsorption pressure was 5 MPa and the pressure difference was 2 MPa. Generally, the water drive promoted the methane diffusion, but if the water drive time was too long, it formed a water plug, and the water drive methane inhibited the diffusion. In shallow reservoirs, water drive can obviously promote the desorption-diffusion of methane. The binding energy between CH4 molecules is mainly composed of the repulsive force, while that between water molecules is mainly the adsorption force. In the binding energy between CH4 molecules and coal structures, the van der Waals (VDW) force accounts for 99% of the effect; in the binding energy between water molecules and coal structures, the electrostatic force contributes 84% to ∼88% thereto. The VDW force is significantly influenced by the pressure, while the electrostatic force is slightly affected. As the water displacement differential pressure is increased, the binding energy between CH4 molecules and coal structures decreases.

Molecular simulation study of adsorption-diffusion of CH4, CO2 and H2O in gas-fat coal

In order to clarify the microscopic dynamics mechanism of CH4, CO2 and H2O adsorption and diffusion in coal, and to reveal the mechanism of the influence of different temperatures and pressures on the adsorption and diffusion characteristics of coal adsorbed CH4, CO2 and H2O molecules. In this paper, the macromolecular structure model of Jixi gas-fat coal was constructed, based on the Giant Canonical Monte Carlo (GCMC) and Molecular Dynamics (MD) methods. The adsorption-diffusion characteristics of CH4,CO2 and H2O single-component gases in the gas-fat coal macromolecule model at temperatures ranging from 273.15 K to 313.15 K and pressures ranging from 0.01 MPa to 15 MPa were investigated by using Material Studio software. The research results indicated that: The adsorption of three gases, CH4, CO2 and H2O, increased with the increase of equilibrium pressure, and the adsorption isotherms conformed to Langmuir type I isotherms. The amount of saturated adsorption of CH4 ranged from 11.18 to 14.37 ml/g, the saturated adsorption of CO2 ranged from 20.40 to 24.70 ml/g, and the saturated adsorption of H2O ranged from 66.61 to 84.21 ml/g. With the increase of temperature, the saturated adsorption of CH4 and CO2 both decreased, and the saturated adsorption of H2O firstly increased and then decreased, and the adsorption of H2O by low temperature and high temperature had both an inhibitory effect on the adsorption of H2O. The potential energy distributions of CH4, CO2 and H2O molecules are poisson distributed. The absolute values of the most available interaction energies are, from highest to lowest: H2O > CO2 > CH4; the activation energies for diffusion of CH4, CO2 and H2O are 12.20 kJ/mol, 3.36 kJ/mol, and 8.47 kJ/mol, respectively, and the diffusion of CO2 is the more likely to occur. The adsorption of CH4 and CO2 in coal is physical adsorption, while the adsorption process of H2O molecules is beyond the scope of physical adsorption. The absolute value of the interaction energy is H2O > CO2 > CH4 in descending order.

Revving Up a Designed Copper Catecholate Porous Organic Polymer for Its Potent Ethylene Adsorption than Ethane.

The potential to produce high-purity C2H4 has made ethylene-selective adsorbents for ethane (C2H6)/ethylene (C2H4) gas mixture separation appealing as viable substitutes for traditional cryogenic distillation. In this aspect, porous organic polymers (POPs) are anticipated to become the next-generation potential adsorbent due to their easily customizable functions and functional sites suitable for gas separation. This article reports the selective C2H4 adsorption over C2H6 using microporous copper(I)-coordinated POP (Cu@Di-POP) via fine-tuning of the π complexation and pore size. The specially designed adsorbent has the ideal pore size and coordinated Cu(I) ions to form π-complexation with C2H4 molecules, which enabled it to adsorb C2H4 (at 1 bar, 24.9, 18.9, and 13.4 cm3 g-1 at 273, 298, and 323 K, respectively) while significantly reducing C2H6 adsorption (at 1 bar, 16.9, 12.7, and 8.8 cm3 g-1 at 273, 298, and 323 K, respectively). At 1 bar, Cu@Di-POP exhibited IAST selectivities of 6.09, 5.60, and 4.13 for C2H4/C2H6 at 273, 298, and 323 K, respectively, suggesting its C2H4 selective behavior, which was further confirmed from the experimental breakthrough measurement. Furthermore, the computational studies carried out with density functional theory highlighted an enhanced charge distribution leading to dπ-pπ conjugation between C2H4 π-electrons and Cu d-electrons, thereby showing a relatively higher interaction energy of -37.23 kcal/mol with C2H4 as compared to -16.06 kcal/mol with C2H6 gas molecules.

Highly selective photocatalytic oxidation of CH4 to CH3OH: A theoretical study

Photooxidation of methane (CH4) in aqueous solution to generate high-value organic compounds is an effective way to replace traditional industrial methods. It is crucial to select catalysts that can avoid competitive reactions and achieve high selectivity. Using first principles calculations, a novel one-dimensional (1D) Ti3C2O2 nanoribbon (NR)/two-dimensional (2D) monolayer MoS2 (MS) heterojunction photocatalyst was ingenious designed in this work, which can achieve the oxidation of CH4 molecules and suppress the execution of competitive reactions. The results indicate that the constructed 1D NR exhibits semiconductor properties and its energy level position meet the requirements of photocatalytic oxidation for CH4. The heterojunction structure composed of NR and MS forms an efficient S-Scheme electron transfer mechanism under illumination, which not only provides sufficient internal driving force for CH4 oxidation, but also effectively avoids the competitive reaction between water molecules and photo-generated holes. Specifically, the photocatalysts exhibits high selectivity and low reaction overpotential for the generation of methanol (CH3OH). This study provides a new perspective for photocatalytic CH4 oxidation and demonstrates the potential application value of 1D MXene in the future field of photocatalysis.

Fabrication of Hofmann-type metal-organic framework based mixed-matrix membranes for efficient CH4/N2 separation

The analogous physical and chemical properties of methane (CH4) and nitrogen (N2) pose a great challenge for their separation. Mixed-matrix membranes (MMMs), combining the good separation performance of fillers and easy processability of polymers, are expected to address this challenging task. In this work, one Hofmann-type metal-organic framework (MOF), CoNi-DABCO, featuring abundant oppositely adjacent open metal sites, narrow pore size, and strong binding affinity toward CH4, is introduced into the polymer of polydimethylsiloxane to fabricate MMMs. The presence of CoNi-DABCO in the membranes could enhance the adsorption capacity for CH4, thus facilitating the transport of CH4 molecules through the membranes. Specially, the MMM containing 20 wt% CoNi-DABCO displays a high CH4 permeability of 1285 Barrer and maintains a good CH4/N2 mixed-gas selectivity of 3.7. Furthermore, the MMMs show good pressure resistance (up to 10 bar) and long-term stability for 30 days. This study suggests the potential of Hofmann-type MOF in the development of high-performance membranes for CH4/N2 separation.