1D Channels Research Articles

A robust mesoporous sulfated zirconium‐doped KIT‐6 solid acid catalyst for the hydrolysis of microcrystalline cellulose

AbstractBACKGROUNDThe exploration of a robust solid acid catalyst for the efficient hydrolysis of cellulose is a research hotspot due to the need for clean production and sustainable development. KIT‐6 silica offers abundant three‐dimensionally interconnected mesopores, which are expected to be superior to mesoporous structures with one‐ or two‐dimensional channels due to faster diffusion of reactants and products during reaction. The catalytic conversion of microcrystalline cellulose is examined in detail over a functionalized KIT‐6 catalyst prepared by the method of Zr addition and subsequent sulfation.RESULTSIn terms of cellulose conversion and product yield, the activity of the catalysts followed the order of sulfated Zr‐KIT‐6 > Zr‐KIT‐6 > SO42−‐KIT‐6 > KIT‐6. Over the sulfated Zr‐KIT‐6 catalyst with a Si/Zr molar ratio of 7:1, a maximum cellulose conversion of 95.0% was achieved with glucose yield of 23.4%, 5‐hydroxymethylfufural yield of 4.9% and levulinic acid yield of 11.7% under the optimized reaction conditions: reaction temperature of 200 °C, reaction time of 2 h, catalyst amount of 0.3 g, cellulose‐to‐water mass ratio of 1:1.CONCLUSIONThe sulfated Zr‐KIT‐6 catalyst possessed the strongest and richest Brønsted acid sites, which readily provided protons for the cleavage of β‐1,4 glycosidic bonds in cellulose, thus conferring superior catalytic activity in cellulose hydrolysis. A plausible pathway at the initial stage of cellulose hydrolysis over the catalyst was proposed. © 2023 Society of Chemical Industry (SCI).

Biomimetic Helical Hydrogen Bonded Organic Framework Membranes for Efficient Uranium Recovery from Seawater.

Inspired by the uranyl-imidazole interactions via nitrogen's (N's) of histidine residues in single helical protein assemblies with open framework geometry that allows through migration/coordination of metal ions. Here, preliminary components of a stable hydrogen-bonded organic framework (HOF) are designed to mimic the stable single helical open framework with imidazole residues available for Uranium (U) binding. The imidazolate-HOF (CSMCRIHOF2-S) is synthesized with solvent-directed H-bonding in 1D array and tuned hydrophobic CH-π interactions leading to single helix pattern having enhanced hydrolytic stability. De-solvation led CSMCRIHOF2-P with porous helical 1D channels are transformed in a freestanding thin film that showcased improved mass transfer and adsorption of uranyl carbonate. CSMCRIHOF2-P thin film can effectively extract ≈14.8mgg-1 in 4 weeks period from natural seawater, with >1.7 U/V (Uranium to Vanadium ratio) selectivity. This strategy can be extended for rational designing of hydrolytically stable, U selective HOFs to realize the massive potential of the blue economy toward sustainable energy.

Aluminum-based metal organic frameworks for greenhouse gases CF4 and C2F6 capture with excellent capacity and selectivity

The capture and recovery of perfluorinated greenhouse gases CF4 and C2F6 from industrial exaust can not only mitigate global warming but also produce value-added products. Adsorption technology based on porous materials is promising for such purpose, while adsorbents with high capacity and selectivity are still lacking due to the chemical inertness of CF4 and C2F6. Herein, three ultra-microporous Al-MOFs with multiple electropositive binding sites in 1D channel were synthesized and evaluated for CF4/C2F6 adsorption. Among the synthesized Al-MOFs, Al-Fum displayed the best adsorption performance due to its desirable pore environment. It has a record-breaking C2F6 adsorption capacity (3.30 mmol/g at 1 bar and 298 K) and C2F6/N2 (10/90, v/v) selectivity (299.6 at 1 bar). In addition, it also displays excellent CF4 adsorption performance, exceeding most of the reported adsorbents. Theoretical simulations demonstrate the high CF4/C2F6 affinity towards Al-Fum is resulted from the multiple interactions of F atoms with H atoms of fumarate linkers and corner hydroxyl groups in frameworks. Moreover, dynamic column breakthrough tests confirmed the excellent separation performance of CF4/N2 and C2F6/N2 on Al-Fum with outstanding regenerability. Due to the green and energy-efficient synthesis method and outstanding adsorption performance, Al-Fum is considered to be an ideal porous material for CF4/C2F6 capture under practical conditions.

Reticular Synthesis of Highly Crystalline Three-Dimensional Mesoporous Covalent-Organic Frameworks for Lipase Inclusion.

The synthesis and application of three-dimensional (3D) mesoporous covalent-organic frameworks (COFs) are still to be developed. Herein, two mesoporous 3D COFs with an stp topology were synthesized in a highly crystalline form with aniline as the modulator. The chemical composition of these COFs was confirmed by Fourier transform infrared (FT-IR) and 13C cross-polarization magic angle spinning nuclear magnetic resonance (NMR) spectroscopies. These 3D mesoporous COFs were highly crystalline and exhibited permanent porosity and good chemical stability in both aqueous and organic media. The space group and unit cell parameters of COF HFPTP-TAE were verified by powder X-ray diffraction (PXRD), small-angle X-ray scattering, and three-dimensional electron diffraction (3D ED). The appropriate pore size of the COF HFPTP-TAE facilitated the inclusion of enzyme lipase PS with a loading amount of 0.28 g g-1. The lipase⊂HFPTP-TAE (⊂ refers to "include in") composite exhibited high catalytic activity, good thermal stability, and a wide range of solvent tolerance. Specifically, it could catalyze the alcoholysis of aspirin methyl ester (AME) with high catalytic efficiency. Oriented one-dimensional (1D) channel mesopores in HFPTP-TAE accommodated lipase, meanwhile preventing them from aggregation, while windows on the wall of the 1D channel favored molecular diffusion; thus, this COF-enzyme design outperformed its amorphous isomer, two-dimensional (2D) mesoporous COF, 3D mesoporous COF with limited crystallinity, and mesoporous silica as an enzyme host.

Decorating Channel Walls in Metal-Organic Frameworks with Crown Ethers for Efficient and Selective Separation of Radioactive Strontium(II).

Nuclear accidents and the improper disposal of nuclear wastes have led to serious environmental radioactive pollutions. The rational design of adsorbents for the highly efficient separation of strontium(II) is essential in treating nuclear waste and recovering radioactive strontium resources. Metal-organic frameworks (MOFs) are potential materials for the separation of aqueous metal ions owing to their designable structure and tunable functionality. Herein, a novel 3D MOF material MOF-18Cr6, in which 1D channels are formed using 18-crown-6-ether-containing ligands as channel walls, is fabricated for strontium(II) separation. In contrast to traditional MOFs designed by grafting functional groups in the framework pores, MOF-18Cr6 possesses regular 18-crown-6-ether cavities on the channel walls, which not only can transport and intake strontium(II) via the channels, but also prevent blockage of the channels after the binding of strontium(II). Consequently, the functional sites are fully utilized to achieve a high strontium(II) removal rate of 99.73 % in simulated nuclear wastewater. This study fabricates a highly promising adsorbent for the separation of aqueous radioactive strontium(II), and more importantly, can provide a new strategy for the rational design of high-performance MOF adsorbents for separating target substances from complex aqueous environments.

Decorating Channel Walls in Metal–Organic Frameworks with Crown Ethers for Efficient and Selective Separation of Radioactive Strontium(II)

AbstractNuclear accidents and the improper disposal of nuclear wastes have led to serious environmental radioactive pollutions. The rational design of adsorbents for the highly efficient separation of strontium(II) is essential in treating nuclear waste and recovering radioactive strontium resources. Metal–organic frameworks (MOFs) are potential materials for the separation of aqueous metal ions owing to their designable structure and tunable functionality. Herein, a novel 3D MOF material MOF‐18Cr6, in which 1D channels are formed using 18‐crown‐6‐ether‐containing ligands as channel walls, is fabricated for strontium(II) separation. In contrast to traditional MOFs designed by grafting functional groups in the framework pores, MOF‐18Cr6 possesses regular 18‐crown‐6‐ether cavities on the channel walls, which not only can transport and intake strontium(II) via the channels, but also prevent blockage of the channels after the binding of strontium(II). Consequently, the functional sites are fully utilized to achieve a high strontium(II) removal rate of 99.73 % in simulated nuclear wastewater. This study fabricates a highly promising adsorbent for the separation of aqueous radioactive strontium(II), and more importantly, can provide a new strategy for the rational design of high‐performance MOF adsorbents for separating target substances from complex aqueous environments.

Surface polydopamine coating to boost molecular permeation of MoS2 lamellar membranes

The rigid MoS2 nanosheets are promising building blocks for establishing straight and regular two-dimensional (2D) channels to pursue high molecule permeances. However, the overtight stacking configuration of MoS2 laminates causes barriers for quick mass transports. In order to solve this issue, we propose the surface modification strategy using polydopamine (PDA) coating on MoS2 nanosheets for lamellar membrane assembly. This approach has the prominent merit of retaining the channel continuity, compared with the conventional intercalation route. Benefitting from the high hydrophilicity of PDA, the 2D PDA@MoS2 (PM) channels stacked by PDA decorated MoS2 sheets are easily solvated and the PM laminates deliver wide channels with d-spacings of up to 1.24 nm under wet states. The permeances of the solvated PM membranes are three times higher than the original MoS2 membranes and are superior to the existing nanofiltration membranes with comparable rejections as well. More interestingly, the PM membrane exhibits pH responsiveness and can achieve thorough sieving for a ternary system by using a single membrane. This study has identified a feasible route to expand the interlayer channels of 2D MoS2 membranes for boosting permeances.

Analysis of Made Lamongan Residential Drainage System Using SWMM (Storm Water Management Model) and HEC-RAS (Hydraulic Engineering Centre-River Analysis System) Models

Made Lamongan Residential is located in an area that has a flat slope and is flanked by two rivers Kali Mengkuli and Kali Gorok, the problem in the study area is that the drainage system is unable to serve rainwater runoff. This is evidenced by the occurrence of inundation during the rainy season with high intensity. The height of the inundation that occurs in the Residential complex ± 60 cm with a reduction in inundation of more than 12 hours. The calculation results showed that there were several sections of the channel that occurred runoff with a planned Q5 flood discharge of 8.14 m3/sec. Based on the results of surveys in the field, many channels were found that had changed their dimensions due to the renovation of residents' houses. In this study, 1D channel hydraulic modelling was carried out using SWMM and HEC-RAS software to obtain a model that was close to the surface runoff conditions at the study site. The purpose of this study is to obtain the greatest handling of inundation in Made Residential in reducing the height of the inundation based on the model to be carried out, as well as obtaining the value of model calibration at the study site.

"Photochemical Surgery" of 1D Metal-Organic Frameworks with a Site-Selective Solubilization/Crystallization Strategy.

One-dimensional (1D) hybrid MOFs are attractive if they consist of different MOF blocks with interconnected channels. However, the precision synthesis of such 1D multiblock MOFs with the desired block lengths and sequences remains a formidable challenge. Herein we propose the "photochemical surgery" method, which combines top-down and bottom-up approaches to enable the site-selective solubilization (removal)/crystallization (reconstruction) of 1D MOFs. We employed photoreactive MOFs, which were prepared by complexing either Cd2+ or Zn2+ with a mixture containing a photochromic bispyridyl ligand (PyDTEopen or PyDTZEopen) and an isophthalate (5-nitroisophthalate (nip2-) or 5-bromoisophthalate (bip2-)). These MOFs were obtained as high-aspect-ratio, needlelike, colorless crystals that bore 1D channels oriented parallel to the long needle axis. When photoreactive DTECdMOFNO2 ([Cd(nip)(PyDTEopen)(H2O)]n), for example, was immobilized at both ends with a metal alloy on a glass substrate and exposed to UV light through a photomask for 60 min in N,N-dimethylformamide/methanol (DMF/MeOH), the unmasked part was removed via solubilization to produce a 50 μm gap. The resulting specimen was immersed for 24 h at 25 °C in DMF/MeOH containing the necessary components for the construction of DTZECdMOFNO2 ([Cd(nip)(PyDTZEopen)(H2O)]n). Eventually, the gap was filled with DTZECdMOFNO2 to produce a triblock hybrid MOF (DTECdMOFNO2-DTZECdMOFNO2-DTECdMOFNO2). The result of a guest diffusion experiment confirmed that the newly formed DTZECdMOFNO2 block shared its 1D channels with the host DTECdMOFNO2 blocks. "Photochemical surgery" can be applied to synthesize 1D hybrid MOFs bearing unconventional sequences and morphologies, e.g., honeycomb- and inverted-honeycomb-patterned hybrids.

Supramolecular Self-Assembly of the Zwitterionic Sn(IV)-Porphyrin Complex

[Sn(OSO3)2(TPyHP)](HSO4)2∙8H2O (1), an ionic Sn(IV)-porphyrin complex, was prepared by reacting [Sn(OH2)2TPyP] with dilute sulfuric acid. X-ray structural analysis revealed that the zwitterionic [Sn(OSO3)2TPyHP]2+ species consists of two anionic axial Sn–O–SO3 units and four peripheral pyridinium moieties, with an overall dicationic charge balanced by two hydrogen sulfate (HSO4−) counter-anions. Ionic hydrogen bonding between the oxygen atoms of axial sulfato ligands and the peripheral pyridinium groups of adjacent Sn(IV)-porphyrin cations led to the formation of a 1D channel filled with counter-anions and water molecules. The supramolecular self-assembly of 1 was further characterized using various spectroscopic techniques, including 1H NMR spectroscopy, elemental analysis, ESI-mass spectrometry, UV-vis spectroscopy, fluorescence spectroscopy, FT-IR spectroscopy, thermogravimetric analysis (TGA), and powder X-ray diffractometry. The zwitterionic [Sn(OSO3)2TPyHP]2+ complex is a structurally well-defined complementary scaffold involved in supramolecular self-assembly. This novel class of ion-assembled metalloporphyrin is a potential functional porphyrin material used in ion exchange applications.

Adenine-based metal–organic framework with 1 D narrow channel for molecular-sieving separation of n-butane and isobutane

Molecular-sieving separation of isomeric C4 paraffins, n-butane (n-C4H10) and isobutane (iso-C4H10), is highly desired but challenging because of their very close molecular sizes and physical properties. However, most of the MOF adsorbents often undergo framework flexibility or ligand rotation or swing, leading to the variation of pore size and the loss of the molecular-sieving effect. In this work, an adenine-based MOF with a suitable window size and rigid narrow 1D channel, namely IPM-101, was selected for n-C4H10/iso-C4H10 separation. Adsorption experiments demonstrate that IPM-101 can sensitively adsorb n-C4H10 in the low-pressure region (0–0.05 bar) and reach a saturation state at 0.1 bar while iso-C4H10 is excluded by the size-exclusion effect. Owing to the high porosity, IPM-101 exhibits a high n-C4H10 adsorption capacity (51.6 cm3 g−1) at 1 bar and 298 K. Density functional theory (DFT) calculations clearly reveal the molecular-sieving mechanism that n-C4H10 molecule can diffuse into the pore channel of IPM-101 easily but the diffusion of iso-C4H10 in IPM-101 is kinetically forbidden for its high diffusion energy barrier. The breakthrough experiments show that n-C4H10 and iso-C4H10 can be efficiently separated and iso-C4H10 with a purity of up to 99.9 % can be directly collected. The regeneration experiments show that IPM-101 has good cycling stability for n-C4H10 adsorption and n-C4H10/iso-C4H10 separation. Therefore, the high separation efficiency, excellent regeneration ability, and low cost indicate that IPM-101 has great application potential for practical n-C4H10/ iso-C4H10 separation in industry.

2D nanofluidic vermiculite membranes with self-confinement channels and recognition sites for ultrafast lithium ion-selective transport

Two-dimensional (2D) membranes with lamina nanofluidic channels hold great promise for ion selective transport. However, the complex nanosheets preparation process and undesirable ion sieving ability of 2D channels in aqueous environment hindered the further application of 2D membranes. Herein, we designed and constructed 2D vermiculite-based nanofluidic membranes with ultrafast lithium ion-selective transport channels through interlayer chemical modification-to introduce sulfonated polyvinyl alcohol (SPVA). As for salt concentration of 0.2 M, the optimal VmMS-1 membrane with stable and sub-nanometer ion selective channels exhibited high Li+ permeation rate up to ∼1.3 mol m−2 h−1 driven by concentration gradient difference, while the selectivity of Li+/Mg2+, Li+/Na+, and Li+/K+ reached 23.8, 14.9, 19.1, respectively. Self-confinement ion recognition (SCIR) mechanism was proposed to describe the superior lithium ion-selective transport process in 2D confined channels. Self-confinement interlayer channel could manipulate the water-shell layer of ions and sulfonic acid groups could effectively recognize lithium ion to accelerate them transport. This study provides a new vermiculite membrane design insight based on SCIR mechanism that is expected to achieve high lithium extraction, as well as providing a new insight of membrane design for other 2D materials.

Bromine versus chlorine substituent in breathing crystals of a copper(I) coordination compound with a triazolamine Schiff base.

It is known that N-[4-(chlorobenzylidene)-4H-1,2,4-triazol-4-amine in reaction with copper(I) perchlorate(VII) forms metastable breathing crystals built up of X-shaped binuclear units containing copper(I) ions in a trigonal coordination sphere. Using trifluoromethanesulfonate instead of perchlorate(VII) affects the self-assembly of the X-shaped units and the breathing function of the resulting crystals. The latter are not breathing crystals. Copper(I) trifluoromethanesulfonate with N-[4-(bromobenzylidene)-4H-1,2,4-triazol-4-amine crystallizes in two forms: open (with the presence of 1D channels) and closed (without 1D channels). Both are characterized by the presence of X-shaped binuclear cationic units and the trigonal coordination sphere of copper(I) ions. The open form has the ability to engage in reversible sorption. The desorption process is associated with the large reorientation of the binuclear units and the reorganization of the intermolecular interactions leading to the closure of the channels. The post-synthetically obtained channel-less form differs from the channel-less form obtained by direct crystallization, the latter being incapable of sorption. The mechanism of the desorption process of the open form is governed by the general principle of dense packing, and the main reason for the sorption process is the formation of directional halogen-halogen interactions. The halogen atom in the para position of the ligands influences the formation of different crystalline forms and also a different mechanism for the desorption process.

Lewis base anchored DhaTph covalent-organic framework for effective capture of thorium(IV) ion

Capture of radioactive thorium (Th) ion from nuclear wastewater is highly necessary. However, current adsorbents show drawback in either adsorption capacity or adsorption rate. In this study, a DhaTph (Dha, 2,5-dihydroxyterephthalaldehyde; Tph, tetra-(p-aminophenyl)porphyrin) covalent-organic framework (COF) with Lewis base sites (C = N and –OH) was applied to capture Th(IV) ions from aqueous solution. DhaTph has a large (d, ∼2 nm) and transparent 1D channel, which makes the active Lewis bases interact with Th(IV) ion easily. Benefited from that, DhaTph exhibits a larger adsorption capacity of 525.0 mg g−1 and rapid adsorption speed (90 min for equilibrium) simultaneously. Besides, this COF owns superior adsorption for Th(IV) ion than various rare earth ions and some other common ions. The systematical characterization and theoretical calculation indicate that the strong chemical chelation interaction from C = N and –OH dominantly contributes to the effective capture of Th(IV) ion. Thus, our work indicates that DhaTph can serve as a potential adsorbent for selective capture of Th(IV) ion, and provides a guideline for designing effective COFs-based adsorbents. We expect this work will promote the application of highly stable COFs in the field of Th(IV) ion capture.

Two-Dimensional Sodium Channels with High Selectivity and Conductivity for Osmotic Power Generation from Wastewater.

Conducting target ions rapidly while rejecting rival ions efficiently is challenging yet highly demanded for ion separation related applications. Two-dimensional (2D) channels are widely used for ion separation, but highly selective 2D channels generally suffer from a relatively low ionic conductivity. Here we report that the 2D vermiculite channels have a Na+ conductivity higher than bulk and at the same time reject heavy metal ions with a selectivity of a few hundreds. Such performance is attributed to the highly electronegative crystal surface and the extremely narrow channel (0.2 nm high), as also supported by the ab initio molecular dynamics simulation. We demonstrate that the highly selective and conductive sodium channels can be utilized to harvest osmotic power from industrial wastewater, achieving a power density of more than 20 W m-2 while preventing pollution from waste heavy metal ions. This work provides a strategy for wastewater utilization as well as treatment. Moreover, the investigation suggests the possibility to break the ionic permeability-selectivity trade-off by combining Ångstrom-scale confinement with proper surface engineering, which could lead to applications that are challenging for previous materials.

Numerical simulation of thixotropic–viscoelastic models for structured fluids in hierarchical grids

In the present work, we implement thixotropic–viscoelastic models in the HiGFlow system, which is a recently developed Computational Fluid Dynamics software that is able to simulate Newtonian, Generalized-Newtonian and viscoelastic flows using finite differences in tree-based grids. The system uses a moving least squares meshless interpolation technique, allowing to use more complex mesh configurations, still keeping the overall order of accuracy. We provide here a brief introduction to each of the implemented models (the Bautista–Manero–Puig, the Modified-Bautista, the NM_τp and NM_T models), where we describe their parameters, their strengths and their limitations. Unlike previous numerical works focused on this kind of fluids, non-zero Reynolds number numerical simulations of these models are carried out here in HiGFlow using different geometries like 2D channels, planar contraction 4:1 and 4:1:4 and our results are compared with those predicted by RheoTool, an open-source toolbox based on OpenFOAM. Although the transient numerical solutions differ, we observe that there is an excellent agreement in the steady-state profiles obtained in both software. A discussion of our results and their physical interpretation, a comparison with previously published results in the literature and a deep analysis of the corner vortex behaviour in the contraction geometries are also presented. Moreover, we show that our methodology offers flexibility and stability in the numerical simulations of thixotropic–viscoelastic flows for structured fluids, which allows the users to accurately simulate rheological behaviour of interest.

Layered double hydroxide nanosheets embedded β-cyclodextrin composite membranes with enhanced chiral separation performance

The technologies for enantiomeric resolution are essential to the development of pharmaceutical industry. The membrane technology has great potential in chiral separation owing to its low cost and high throughput; however, the enantioselective of membrane is limited by the thickness of the active layer, which is closely related to the number of theoretical separation plates. In this work, the layered double hydroxides (LDH) are synthesized by hydrothermal process and then vacuum filtrated with β-cyclodextrin (β-CD) and polyvinyl alcohol (PVA) on a porous substrate to fabricate chiral selective membranes. 2D channels with increased number of separation stages are formed in the selective layer after heat post-treatment. The enantiomeric excesses value is enhanced from 10.95% to 24.32% for racemic L/D- tryptophan resolution. This work provides a new approach for designing high performance chiral separation membranes from the aspect of increasing the transport path.

A Post‐Spinel NaFeSnO4 as Novel Narrow Band Gap Photocatalyst for Visible Light Assisted Decomposition of Crystal Violet Dye

AbstractSnO2 is a wide bandgap photocatalyst, and Fe2O3 is susceptible to the recombination of photocharges produced is heterogenized in the form of NaFeSnO4. NaFeSnO4 with post‐spinel structure having one‐dimenisonal (1D) channel is explored first time as photocatalyst. Phase purity and structure of NaFeSnO4 was examined using X‐ray diffraction (XRD). Particle morphology, light absorption behavior, band‐gap energy estimation and surface area of NaFeSnO4 were evaluated using various instrumental techniques. Extent of charge separation and charge transfer was investigated using photoluminescence (PL) analysis and electrochemical impedance spectroscopy (EIS). Photocatalytic performance of NaFeSnO4 was examined for degradation of crystal violet dye by irradiating visible light. The photocatalytic properties of NaFeSnO4 are compared with the precursor oxides Fe2O3 and SnO2. It has been demonstrated first time that NaFeSnO4 is an efficient visible light active photocatalyst than Fe2O3 and SnO2 for degradation of crystal violet dye.

Novel Mixed-Dimensional hBN-Passivated Silicon Nanowire Reconfigurable Field Effect Transistors: Fabrication and Characterization.

This work demonstrates the novel concept of a mixed-dimensional reconfigurable field effect transistor (RFET) by combining a one-dimensional (1D) channel material such as a silicon (Si) nanowire with a two-dimensional (2D) material as a gate dielectric. An RFET is an innovative device that can be dynamically programmed to perform as either an n- or p-FET by applying appropriate gate potentials. In this work, an insulating 2D material, hexagonal boron nitride (hBN), is introduced as a gate dielectric and encapsulation layer around the nanowire in place of a thermally grown or atomic-layer-deposited oxide. hBN flake was mechanically exfoliated and transferred onto a silicon nanowire-based RFET device using the dry viscoelastic stamping transfer technique. The thickness of the hBN flakes was investigated by atomic force microscopy and transmission electron microscopy. The ambipolar transfer characteristics of the Si-hBN RFETs with different gating architectures showed a significant improvement in the device's electrical parameters due to the encapsulation and passivation of the nanowire with the hBN flake. Both n- and p-type characteristics measured through the top gate exhibited a reduction of hysteresis by 10-20 V and an increase in the on-off ratio (ION/IOFF) by 1 order of magnitude (up to 108) compared to the values measured for unpassivated nanowire. Specifically, the hBN encapsulation provided improved electrostatic top gate coupling, which is reflected in the enhanced subthreshold swing values of the devices. For a single nanowire, an improvement up to 0.97 and 0.5 V/dec in the n- and p-conduction, respectively, is observed. Due to their dynamic switching and polarity control, RFETs boast great potential in reducing the device count, lowering power consumption, and playing a crucial role in advanced electronic circuitry. The concept of mixed-dimensional RFET could further strengthen its functionality, opening up new pathways for future electronics.

Microporous Cd-MOF as multifunctional material for rapid and visual luminescence sensing of Fe3+, MnO4− and TNP in water and efficient CO2 catalytic conversion

The excessive discharge of Fe3+, MnO4−, TNP and CO2 has resulted in serious environmental problems, which needs to be resolved urgently. Herein, a stable multifunctional Cd2+-organic framework, [Cd(H4L)]·2DMF·8H2O (Cd-MOF-1) was successfully constructed by using the ligand 4,4′,4″,4‴- (1,4-phenylenebis (1H-imidazole-2,4,5-triyl))tetrabenzoic acid (H6L) and Cd(NO3)2·2.5H2O under solvothermal conditions. Structural analysis revealed that Cd-MOF-1 possessed a 3D framework with rich Lewis acid sites (unsaturated Cd2+ sites), Brønsted acid sites (protonated imidazole moieties) and uncoordinated carboxylate oxygens in the hexagonal 1D channels. Moreover, Cd-MOF-1 exhibits good stability in acid-base aqueous solutions with pH = 4–12. Apart from the above structural features, Cd-MOF-1 also displays intense luminescence emission, which can be used to quickly and sensitively detect Fe3+, MnO4−and TNP in aqueous solutions with a high quenching constant and low detection limit even in the presence of other competition ions. Especially, the response time of the Cd-MOF-1 for Fe3+ ions was only 5 s, which is very short response time among the previous MOFs used for Fe3+ detection. Besides, we successfully constructed Cd-MOF-1/PEO mixed matrix films, which can achieve visualized quick detection of Fe3+, MnO4−and TNP in aqueous solutions under the UV lamp. In addition, activated Cd-MOF-1 (called Cd-MOF-1a) with all the guest molecules removed by heating delineates medium shows CO2 gas adsorption and efficient CO2 fixation with epoxide into cyclic carbonate under relatively mild and solvent-free conditions. On top of that, Cd-MOF-1 can be reused at least five cycles with excellent luminescence efficiency and catalytic activity. Furthermore, the possible luminescence sensing and catalytic mechanisms have also been discussed in detail. This work gives a new multifunctional platform for luminescence sensing and CO2 fixation.