Sulfur Edge Research Articles

Heterogeneous Carbonylation of Alcohols on Charge‐Density‐Distinct Mo−Ni Dual Sites Localized at Edge Sulfur Vacancies

AbstractAlcohols carbonylation is of great importance in industry but remains a challenge to abandon the usage of the halide additives and noble metals. Here we report the realization of direct alcohols heterogeneous carbonylation to carbonyl‐containing chemicals, especially in methanol carbonylation, with a remarkable space‐time‐yield (STY) of 4.74 molacetyl/kgcat./h and a durable stability as long as 100 h on Ni@MoS2 catalyst. Mechanistic analysis reveals that the Mo−Ni dual sites localized at edge sulfur vacancies of Ni@MoS2 exhibit distinct charge density, which strongly activate CH3OH to break its C−O bond and non‐dissociatively activate CO. Density functional theory calculations further suggest that the low charge density in Mo−Ni, the Ni site, could significantly lower the barrier for CO migration and nucleophilic attack of methoxy species, and finally leads to the rapid formation of acetyl products. Ni@MoS2 catalyst could also effectively realize the carbonylation of ethanol, n‐propanol and n‐butanol to their acyl products, which may demonstrate its universal application for alcohols carbonylation.

X-ray photoelectron and NEXAFS spectroscopy of thionated uracils in the gas phase.

We present a comprehensive, combined experimental and theoretical study of the core-level photoelectron and near-edge x-ray absorption fine structure (NEXAFS) spectra of 2-thiouracil, 4-thiouracil, and 2,4-dithiouracil at the oxygen 1s, nitrogen 1s, carbon 1s, and the sulfur 2s and 2p edges. X-ray photoelectron spectra were calculated using equation-of-motion coupled-cluster theory (EOM-CCSD), and NEXAFS spectra were calculated using algebraic diagrammatic construction and EOM-CCSD. For the main peaks at O and N 1s as well as the S 2s edge, we find a single photoline. The S 2p spectra show a spin-orbit splitting of 1.2eV with an asymmetric vibrational line shape. We also resolve the correlation satellites of these photolines. For the carbon 1s photoelectrons, we observe a splitting on the eV scale, which we can unanimously attribute to specific sites. In the NEXAFS spectra, we see very isolated pre-edge features at the oxygen 1s edge; the nitrogen edge, however, is very complex, in contrast to the XPS findings. The C 1s edge NEXAFS spectrum shows site-specific splitting. The sulfur 2s and 2p spectra are dominated by two strong pre-edge transitions. The S 2p spectra show again the spin-orbit splitting of 1.2eV.

Chitosan-derived N-doped carbon supported Cu/Fe co-doped MoS2 nanoparticles as peroxymonosulfate activator for efficient dyes degradation

Peroxymonosulfate (PMS), which is dominated by free radical (SO4•-) pathway, has a good removal effect on organic pollutants in complex water matrices. In this article, a new catalyst (CFM@NC) was synthesized by hydrothermal carbonization method with chitosan (CS) as N and C precursors, and used to activate PMS to degrade dye wastewater. CFM@NC/PMS system can degrade 50 mg·L−1 rhodamine B by 99.59 % within 30 min, and the degradation rate remains as high as 97.32 % after 5 cycles. It has good complex background matrices, acid-base anti-interference ability (pH 2.6–10.1), universality and reusability. It can degrade methyl orange and methylene blue by >98 % within 30 min. The high efficiency of the composite is due to the fact that CS-modified MoS2 as a carrier exposes a large number of active sites, which not only disperses CuFe2O4 nanoparticles and improves the stability of the catalyst, but also provides abundant electron rich groups, which promotes the activation of PMS and the production of reactive oxygen species (ROS). PMS is effectively activated by catalytic sites (Cu+/Cu2+, Fe2+/Fe3+, Mo4+/Mo6+, pyridine N, pyrrole N, edge sulfur and hydroxyl group) to produce a large number of radicals to attack RhB molecules, causing chromophore cleavage, ring opening, and mineralization. Among them, free radical SO4•- is the main ROS for RhB degradation. This work is expected to provide a new idea for the design and synthesis of environmentally friendly and efficient heterogeneous catalysts.

Construction of S-doped cellulose nanocrystals with edge sulfur vacancies to enhance the generation of 1O2 and promote peroxymonosulfate (PMS) activation

The strategy of constructing edge sulfur vacancies at cellulose surface interfaces has attracted widespread interest in fields such as electronics, photonics, optoelectronics, electrocatalysis, environmental remediation, and biosensing. In this study, NiCo2S4 (NCS) was modified onto cellulose sulfide nanocrystals (SCNC) with chiral helical structures. Utilizing high energy β Particle bombardment on the surface of photocatalysts induces the generation of edge S vacancies in SCNC, while promoting the formation of heterometallic single-atom clusters (Con, Nin) in NCS. The edge sulfur vacancies on the surface of SCNC exhibit high reactivity and adsorption capacity. The aggregation of Co and Ni at this position can transfer photo generated electrons to the edge sulfur vacancies, thereby protecting the edge sulfur vacancies and prolonging the carrier lifetime. Electrons enriched in edge S vacancies can activate the O–O bond of PMS, thereby achieving efficient degradation of ciprofloxacin (CIP). The degradation kinetics constant of Con-Nin/NCS/SCNC-Sv/PMS is 1.69 times higher than that of NCS/SCNC/PMS. In addition, electron paramagnetic resonance (EPR) shows that the sample produces a large amount of 1O2 during photocatalysis This article constructs a new approach for protecting edge S vacancies with heterogeneous single atom clusters, providing a new perspective for achieving efficient photocatalytic degradation of CIP.

Speciation and Possible Origins of Organosulfur Compounds in Rice Paddy Soils Affected by Acid Mine Drainage.

Although sulfur cycling in acid mine drainage (AMD)-contaminated rice paddy soils is critical to understanding and mitigating the environmental consequences of AMD, potential sources and transformations of organosulfur compounds in such soils are poorly understood. We used sulfur K-edge X-ray absorption near edge structure (XANES) spectroscopy to quantify organosulfur compounds in paddy soils from five AMD-contaminated sites and one AMD-uncontaminated reference site near the Dabaoshan sulfide mining area in South China. We also determined the sulfur stable isotope compositions of water-soluble sulfate (δ34SWS), adsorbed sulfate (δ34SAS), fulvic acid sulfur (δ34SFAS), and humic acid sulfur (δ34SHAS) in these samples. Organosulfate was the dominant functional group in humic acid sulfur (HAS) in both AMD-contaminated (46%) and AMD-uncontaminated paddy soils (42%). Thiol/organic monosulfide contributed a significantly lower proportion of HAS in AMD-contaminated paddy soils (8%) compared to that in AMD-uncontaminated paddy soils (21%). Within contaminated soils, the concentration of thiol/organic monosulfide was positively correlated with cation exchange capacity (CEC), moisture content (MC), and total Fe (TFe). δ34SFAS ranged from -6.3 to 2.7‰, similar to δ34SWS (-6.9 to 8.9‰), indicating that fulvic acid sulfur (FAS) was mainly derived from biogenic S-bearing organic compounds produced by assimilatory sulfate reduction. δ34SHAS (-11.0 to -1.6‰) were more negative compared to δ34SWS, indicating that dissimilatory sulfate reduction and abiotic sulfurization of organic matter were the main processes in the formation of HAS.

Unraveling high efficiency multi-step sodium storage and bidirectional redox kinetics synergy mechanism of cobalt-doping vanadium disulfide anode

Sodium-based storage devices based on conversion-type metal sulfide anodes have attracted great attention due to their multivalent ion redox reaction ability. However, they also suffer from sodium polysulfides (NaPSs) shuttling problems during the sluggish Na+ redox process, leading to “voltage failure” and rapid capacity decay. Herein, a metal cobalt-doping vanadium disulfide (Co-VS2) is proposed to simultaneously accelerate the electrochemical reaction of VS2 and enhance the bidirectional redox of soluble NaPSs. It is found that the strong adsorption of NaPSs by V-Co alloy nanoparticles formed in situ during the conversion reaction of Co-VS2 can effectively inhibit the dissolution and shuttle of NaPSs, and thermodynamically reduce the formation energy barrier of the reaction path to effectively drive the complete conversion reaction, while the metal transition of Co elements enhances reconversion kinetics to achieve high reversibility. Moreover, Co-VS2 also produce abundant sulfur vacancies and unsaturated sulfur edge defects, significantly improve ionic/electron diffusion kinetics. Therefore, the Co-VS2 anode exhibits ultrahigh rate capability (562 mA h g−1 at 5 A g−1), high initial coulombic efficiency (≈90%) and 12,000 ultralong cycle life with capacity retention of 90% in sodium-ion batteries (SIBs), as well as impressive energy/power density (118 Wh kg−1/31,250 W kg−1) and over 10,000 stable cycles in sodium-ion hybrid capacitors (SIHCs). Moreover, the pouch cell-type SIHC displays a high-energy density of 102 Wh kg−1 and exceed 600 stable cycles. This work deepens the understanding of the electrochemical reaction mechanism of conversion-type metal sulfide anodes and provides a valuable solution to the shuttling of NaPSs in SIBs and SIHCs.

Effect of UV-O3 treatment on the performance of UV detector based on zinc oxide/molybdenum disulfide nanosheet heterostructures

UV photodetectors based on ZnO nanostructures, using a metal-semiconductor-metal (MSM) configuration, are popular due to their simple fabrication. However, they experience high dark currents and slow photoresponse speeds. This is due to a high recombination rate for photogenerated electrons and holes as well as low charge carrier mobility attributable to ZnO's inherent defects. In this study, MoS2 nanosheets was employed to cover the surface of ZnO nanorods, creating a unique architecture that focuses the impact of MoS2 solely on light absorption and charge transfer on the ZnO surface. Subsequently, a 15-min UV-O3 exposure is applied to the ZnO/MoS2 structure. The ZnO/MoS2UVo heterostructure exhibits remarkable results, including a six-fold increase in sensitivity compared to pure ZnO, Additionally, the Detectivity increases by 265 %, while the Responsivity and Quantum Efficiency rise by up to 102 %. These enhancements are attributed to the reduction of dark current coming from the reduction of oxygen vacancies as sulfur edge atoms from MoS2 fill these vacancies. Furthermore, additional dark current reduction post UV-O3 treatment is due to both the reduced ZnO oxygen vacancies and the formation of a thin MoO3 passivation layer on the ZnO NR surface. Despite these achievements, the study acknowledges the presence of multiple junctions between ZnO, MoS2, and MoO3, which still pose challenges for efficient charge transfer to the electrodes.

Edge Magnetism in MoS2 Nanoribbons: Insights from a Simple One-Dimensional Model.

Edge magnetism in zigzag nanoribbons of monolayer MoS2 has been investigated with both density functional theory and a tight-binding plus Hubbard (TB+U) Hamiltonian. Both methods revealed that one band crossing the Fermi level is more strongly influenced by spin polarization than any other bands. This band originates from states localized on the sulfur edge of the nanoribbon. Its dispersion closely resembles that of the energy branch obtained in a linear chain of atoms with first-neighbor interaction. By exploiting this resemblance, a toy model has been designed to study the energetics of different spin configurations of the nanoribbon edge.

Ultrasensitive room-temperature flexible ammonia gas sensor based on Au-functionalized polypyrrole wrapped enriched edge sulfur vacancies MoS2 nanosheets

Au/MoS2/polypyrrole (Au/MoS2/PPy) nanocomposite is successfully synthesized by the liquid-phase ultrasonic exfoliation process combined with in-situ polymerization method and then Au particles are decorated on its surface. Abundant sulfur (S) vacancies in the exfoliated layered MoS2 nanosheets act as active adsorption sites, and Au particles also play an efficient catalyst to enhance the NH3 gas sensing properties of Au/MoS2/PPy flexible sensor at room temperature. It results in higher NH3 gas sensing response, faster recovery rate, and more stable sensing performance even under complex environment conditions such as high relative humidity and high bending angle/numbers compared with that of pristine PPy sensor. The enhancement sensing mechanisms of Au/MoS2/PPy sensor are attributed to the p-n heterojunction between layered MoS2 and PPy, the active sites of S vacancies, the catalysis and dehydrogenation effect of Au particles, which have been verified by XPS, current-voltage (I-V), and in-situ FITR, etc. Moreover, the density-functional theory (DFT) calculations are employed to further illustrate the selectivity sensing mechanism, and reveal the S vacancies, the nanocomposite of MoS2/PPy possess high superiority for improving NH3 sensing properties at room temperature.

Ultra-fast uranium capture via the synergistic interaction of the intrinsic sulfur atoms and the phosphoric acid groups adhered to edge sulfur of MoS2

In order to deal with the sudden nuclear leakage event to suppress the spread of radioactive contaminants in a short period of time, it is extremely urgent needed to explore an adsorbent that could be capable of in-situ remedial actions to rapidly capture the leaked radionuclides in split second. An adsorbent was developed that MoS2 via ultrasonic to expose more surface defects afterwards functionalized by phosphoric acid resulting in more active sites being endowed on the edge S atoms of Mo-vacancy defects, while simultaneously increased the hydrophilicity and interlayer spacing. Hence, an overwhelming fast adsorption rates (adsorption equilibrium within 30 s) are presented and place the MoS2-PO4 at the top of performing sorbent materials. Moreover, the maximum capacity calculated from Langmuir model is as high as 354.61 mg·g−1, the selective adsorption capacity (SU) achieving 71.2% in the multi-ion system and with more than 91% capacity retention after 5 cycles of recycling. Finally, XPS and DFT insight into the adsorption mechanism, which can be explained as interaction of UO22+ on the surface of MoS2-PO4 by forming U-O and U-S bonds. The successful fabrication of such a material may provide a promising solution for emergency treatment of radioactive wastewater during nuclear leakage events.

Cost-Effective and Highly Efficient Manganese-Doped MoS2 Nanosheets as Visible-Light-Driven Photocatalysts for Wastewater Treatment.

One of the main objectives in wastewater treatment and sustainable energy production is to find photocatalysts that are favorably efficient and cost-effective. Transition-metal dichalcogenides (TMDs) are promising photocatalytic materials; out of all, MoS2 is extensively studied as a cocatalyst in the TMD library due to its exceptional photocatalytic activity for the degradation of organic dyes due to its distinctive morphology, adequate optical absorption, and rich active sites. However, sulfur ions on the active edges facilitate the catalytic activity of MoS2. On the basal planes, sulfur ions are catalytically inactive. Injecting metal atoms into the MoS2 lattice is a handy approach for triggering the surface of the basal planes and enriching catalytically active sites. Effective band gap engineering, sulfur edges, and improved optical absorption of Mn-doped MoS2 nanostructures are promising for improving their charge separation and photostimulated dye degradation activity. The percentage of dye degradation of MB under visible-light irradiations was found to be 89.87 and 100% for pristine and 20% Mn-doped MoS2 in 150 and 90 min, respectively. However, the degradation of MB dye was increased when the doping concentration in MoS2 increased from 5 to 20%. The kinetic study showed that the first-order kinetic model described the photodegradation mechanism well. After four cycles, the 20% Mn-doped MoS2 catalysts maintained comparable catalytic efficacy, indicating its excellent stability. The results demonstrated that the Mn-doped MoS2 nanostructures exhibit exceptional visible-light-driven photocatalytic activity and could perform well as a catalyst for industrial wastewater treatment.

Polysulfide induced synthesis of a MoS2 self-supporting electrode with wide-layer-spacing for efficient electrocatalytic water splitting.

Efficient non-noble metal bifunctional electrocatalysts can increase the conversion rate of electric energy in the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Herein, a ball & sheet MoS2/Ni3S2 composite with wide-layer-spacing and high 1T-rich MoS2 is assembled on nickel foam (NF) via a two-step solvothermal method with polymeric sulfur (S-r-DIB) as the sulfur source. The obtained material serves as both the cathode and the anode toward overall water splitting in an alkaline electrolyte. The results proved that the interpenetration of MoS2/Ni3S2-p with a ball and sheet structure increased the material active surface area and exposed more catalytic active sites, which contributed to the penetration of solution and the transfer of charge/hydrion. Meanwhile, two different semiconductors of MoS2 and Ni3S2 along with the presence of ample active sulfur edge sites and few-layer, wide-layer-spacing structures of MoS2 lead to an outstanding electrocatalytic activity. In particular, the electrodes of MoS2/Ni3S2-p only need a battery voltage of 1.55 V at 10 mA cm-2. The bifunctional electrocatalyst MoS2/Ni3S2-p also shows excellent stability at large current densities during the electrochemical test.

A DFT study of site-dependent energetics of hexagonal MoS[formula omitted] nanoparticles under varying reaction conditions

A plane wave periodic density functional theory study of a representative hexagonal shaped MoS2 nanoparticle is conducted to compute the site-dependent energetics of the catalyst under different operating conditions. It is shown that the (1) energy for vacancy formation and the associated free energy profile of the reaction steps involved in creating the vacancy and (2) the binding energy of hydrogen and other probe atoms such as CO and lutidine, are all dependent on the location of the associated sulfur or molybdenum atom and the edge type (i.e. metal or sulfur edge). In particular, sulfur atoms near the corner are more strongly bound than those in the interior of the metal edge. Further, a larger metal-sulfur bond strength results in lower binding energy of hydrogen on that sulfur atom which in turn implies that this hydrogen is more Brønsted acidic in nature. These results indicate that the nature and the location of active sites on MoS2 is heavily dependent on the nature of the reaction that is being catalyzed and the corresponding operating conditions.

Comparison of Co-Mo-S and remote control model for designing efficient Co-doped MoS2 hydrodeoxygenation catalysts

Co-promoted MoS2 catalysts as good candidates can effectively remove the oxygen in bio-oil through the hydrodeoxygenation (HDO) of phenolics. However, it is of great importance to maximize the synergistic effect between Co and MoS2 which is conductive to the design of highly efficient Co-doped MoS2 HDO catalysts. Herein, two model catalysts with Co-Mo-S and CoS2/MoS2 (remote control model) as the active phases were successfully constructed and evaluated in the HDO of p-cresol. It was found that Co-Mo-S catalyst showed a significantly higher intrinsic HDO activity than CoS2/MoS2 catalyst, and the synergy factor between Co dopant and MoS2 of Co-Mo-S was 3.1 times that of CoS2/MoS2. The greatly enhanced HDO performance of Co-Mo-S catalyst is attributed to remarkably weakened strength of MoS bond, which can facilitate the sulfur vacancies (Vs) formation on the sulfur edges and promote the reaction rate of direct deoxygenation (DDO) pathway. This work revealed that Co-Mo-S model could better promote the CoMo synergy than the remote control model so as to design more efficient MoS2-based catalysts for HDO reactions.

Sulfur Encapsulation and Sulfur Doping Synergistically Enhance Sodium Ion Storage in Microporous Carbon Anodes.

MOF-based materials are a class of efficient precursors for the preparation of heteroatom-doped porous carbon materials that have been widely applied as anode materials for Na-ion batteries. Thereinto, sulfur is often introduced to increase defects and act as an active species to directly react with sodium ions. Although the sulfur introduction and high surface area can synergistically improve capacity and rate capability, the initial Coulombic efficiency (ICE) and electrical conductivity of carbon material are inevitably reduced. Therefore, balancing sodium storage capacity and ICE is still the bottleneck faced by adsorbent carbon materials. Here, sulfur-encapsulated microporous carbon material with nitrogen, sulfur dual-doping (NSPC) is synthesized by postprocessing, achieving the reduced specific surface area by encapsulating sulfur in micropores, and the increased active sites by edge sulfur doping. The synergy between encapsulation and sulfur doping effectively balances specific capacity, rate capability, and ICE. The NSPC material exhibits capacities of 591.5 and 244.2 mAh g-1 at 0.5 and at 10 A g-1, respectively, and the ICE is as high as 72.3%. Moreover, the effect of nitrogen and sulfur on the improvement of electron/ion diffusion kinetics is resonantly demonstrated by density functional theory calculations. This synergistic preparation method may reveal a feasible thought for fabricating excellent-performance adsorption-type carbon materials for Na-ion batteries.

Engineering unsaturated sulfur site in three-dimension MoS2@rGO nanohybrids with expanded interlayer spacing and disordered structure for gaseous elemental mercury trap

Rapid and effective capture of gaseous elemental mercury (Hg0) over a wide operating temperature range is significant for the green and sustainable development of nonferrous smelting industry. High mercury affinity and strong sulfur resistance of two-dimensional layered MoS2 render it an outstanding adsorbent for Hg0 trap. However, the relative lack of serviceable active sites greatly suppresses its extensive application. Herein, a feasible strategy to expand interlayer spacing, build disordered structure and engineer unsaturated sulfur adsorption sites was provided through the construction of three-dimension MoS2@rGO nanohybrids. As expected, compared with bulk and ordered MoS2, the prepared MoS2@rGO hybrid exhibits a remarkable performance improvement for Hg0 adsorption. The average Hg0 adsorption rate of MoS2@rGO is 2.28 μg/g/min and its saturated adsorption capacity reaches 20.91 mg/g. The typical components in nonferrous flue gas have almost no effect on Hg0 adsorption performance. X-ray photoelectron spectroscopy confirms that the formation of abundant unsaturated coordination sulfurs sites with high thermostability is critical for Hg0 adsorption performance improvement. Moreover, the density functional theory calculation results further demonstrate the high adsorption activity of unsaturated coordination sulfur sites for Hg0 capture. Among these sulfur sites, edge sulfur vacancy site plays a dominant role for Hg0 adsorption because of the lowest Hg0 adsorption energy. The final adsorption production is HgS which has negligible environmental toxicity due to its extreme stability. This work not only provides a promising adsorbent for Hg0 removal in industrial application, but also opens up an avenue to engineer unsaturated sulfur for other layered transition metal dichalcogenides.

Self‐Passivated Metal Klein Edge of 1T‐Phase Transition Metal Dichalcogenides and the Induced High‐Efficient Hydrogen Evolution Reaction Activity

AbstractThe pristine edge of a 2D material generally undergoes an edge self‐passivation into its ground‐state configuration. To date, several self‐passivated edges of 1H‐phase transition metal dichalcogenides (TMDCs) have been reported in theories and experiments. However, no self‐passivated edges of its sister material 1T‐phase TMDCs are found. Here, taking 1T‐VS2 as an example, a self‐passivated V2 dimer‐like metal Klein (DM‐Klein) edge of 1T‐TMDCs is reported. It exhibits high thermodynamic stability and can spontaneously form at V‐rich chemical potential conditions. Unexpected intermetallic d–d orbital interaction of edge metal atoms results in metal dimerization. This edge self‐passivation mode is universal in group IV and V 1T‐TMDCs. Furthermore, strong intermetallic interaction and appropriate edge sulfur saturation make DM‐Klein edges of 1T‐TMDCs show excellent catalytic activity in the hydrogen evolution reaction compared to that of well‐known Pt(111) surface. This study provides opportunities for the further practical application of 1T‐TMDCs in catalysts.

Selective-Epitaxial Hybrid of Tripartite Semiconducting Sulfides for Enhanced Solar-to-Hydrogen Conversion.

The design and synthesis of advanced semiconductors is crucial for the full utilization of solar energy. Herein, colloidal selective-epitaxial hybrid of tripartite semiconducting sulfides CuInS2 Cd(In)SMoS2 heteronanostructures (HNs) via lateral- and vertical-epitaxial growths, followed by cation exchange reactions, are reported. The lateral-epitaxial CuInS2 and Cd(In)S enable effective visible to near-infrared (NIR) solar spectrum absorption, and the vertical-epitaxial ultrathin MoS2 offer sufficient edge sulfur sites for the hydrogen evolution reaction (HER). Furthermore, the integrated structures exhibit unique epitaxial-staggered type II band alignments for continuous charge separation. They achieve the H2 evolution rate up to 8 mmol h-1 g-1 , which is ≈35 times higher than bare CdS and show no deactivation after long-term cycling, representing one of the most efficient and robust noble-metal-free photocatalysts. This design principle and transformation protocol open a new way for creating all-in-one multifunctional catalysts in a predictable manner.

Boxlike Assemblages of Few-Layer MoS2 Nanosheets with Edge Blockage for High-Efficiency Hydrogenation of CO2 to Methanol

Direct hydrogenation of CO2 into methanol is a promising strategy for reducing excessive dependence on fossil fuels and alleviating environmental concerns. Recently, in-plane sulfur vacancies in two-dimensional MoS2 nanosheets were unveiled as efficient catalytic active sites for methanol synthesis from CO2, whereas edge vacancies facilitated hydrogenation of CO2 to methane. Herein, we developed boxlike assemblages of quasi-single-layer MoS2 nanosheets, which were edge-blocked by ZnS crystallites (denoted as h-MoS2/ZnS) via a metal–organic framework (MOF)-engaged solvothermal route and subsequent heat treatments. The spatial confinement of the ZnS can restrain the growth and aggregation of MoS2 and ensure the stability of few-layer or even single-layer MoS2 in the assemblages. More importantly, the presence of ZnS can prevent reactants from approaching the edge sulfur vacancies of MoS2. With more exposed in-plane sulfur vacancies and less edge sulfur vacancies, the h-MoS2/ZnS exhibits 67.3% methanol selectively, 9.0% CO2 conversion, and a high methanol space-time yield of up to 0.93 gMeOH·gMoS2–1·h–1 at 260 °C, 5 MPa, and 15 000 mL·gcat.–1·h–1. The catalytic activity was stable for at least 120 h. By removing the ZnS phase from h-MoS2/ZnS and thus deliberately creating more edge sulfur vacancies, it was further confirmed that edge sulfur vacancies are active catalytic sites for excessive hydrogenation of CO2 to methane. Furthermore, the reaction mechanism of our catalyst was also investigated by a high-pressure in situ DRIFTS study. Thus, this MOF-templated strategy for assembling and confining quasi-single-layer MoS2 provides insights into the development of highly efficient transition-metal dichalcogenide catalysts for CO2 hydrogenation with excellent stability.

Ionic Liquid Decelerates Single-Stranded DNA Transport through Molybdenum Disulfide Nanopores.

Nanopores in two-dimensional (2D) materials have emerged to offer in principle necessary spatial resolution for high-throughput DNA sequencing. However, their fidelity is severely limited by the fast DNA translocation. A recent experiment indicates that introducing ionic liquids could slow down DNA translocation in a MoS2 nanopore. However, the corresponding in-depth molecular mechanism underlying the experimental findings is not fully understood, which is crucial for the future improvement of rational DNA translocation control. Here, we computationally investigate and then experimentally identify the effect of BmimCl ionic liquid on the retardation of ssDNA translocation through a single-layer MoS2 nanopore. Our all-atom molecular dynamics simulations demonstrate that the strong interaction between Bmim+ and ssDNA offers a considerable dragging force to decelerate the electrophoretic motion of ssDNA in the BmimCl solution. Moreover, we show that Bmim+ ions exhibit preferential binding on the sulfur edges of the nanopore. These Bmim+ in the pore region can not only act as a steric blockage but also form π-π stackings with nucleobases, which provide a further restriction on the ssDNA motion. Therefore, our molecular dynamics simulation investigations deepen the understanding of the critical role of ionic liquid in DNA translocation through a nanopore from a molecular landscape, which may benefit practical implementations of ionic liquids in nanopore sequencing.