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Recent Submissions

  • Spin transport in multilayer graphene away from the charge neutrality point

    He, Xin; Wen, Yan; Zhang, Chenhui; Li, Peng; Zheng, Dongxing; Chen, Aitian; Manchon, Aurelien; Zhang, Xixiang (Carbon, Elsevier BV, 2020-10-17) [Article]
    Graphene is considered as a promising material in spintronics due to its long spin relaxation time and long spin relaxation length. However, its spin transport properties have been studied at low carrier density only, beyond which much is still unknown. In this study, we explore the spin transport and spin precession properties in multilayer graphene at high carrier density using ionic liquid gating. We find that the spin relaxation time is directly proportional to the momentum relaxation time, indicating that the Elliott-Yafet mechanism still dominates the spin relaxation in multilayer graphene away from the charge neutrality point.
  • Bulk and Interfacial Properties of the Decane + Water System in the Presence of Methane, Carbon Dioxide, and Their Mixture

    Yang, Yafan; Nair, Arun Kumar Narayanan; Anwari Che Ruslan, Mohd Fuad; Sun, Shuyu (The Journal of Physical Chemistry B, American Chemical Society (ACS), 2020-10-16) [Article]
    Molecular dynamics simulations are carried out to study the two-phase behavior of the n-decane + water system in the presence of methane, carbon dioxide, and their mixture under reservoir conditions. The simulation studies were complemented by theoretical modeling using the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state (EoS) and density gradient theory. Our results show that the presence of methane and carbon dioxide decreases the interfacial tension (IFT) of the decane + water system. In general, the IFT increases with increasing pressure and decreasing temperature for the methane + decane + water and carbon dioxide + decane + water systems, similar to what has been found for the corresponding decane + water system. The most important finding of this study is that the presence of carbon dioxide decreases the IFT of the methane + decane + water system. The atomic density profiles provide evidence of the local accumulation of methane and carbon dioxide at the interface, in most of the studied systems. The results of this study show the preferential dissolution in the water-rich phase and enrichment at the interface for carbon dioxide in the methane + carbon dioxide + decane + water system. This indicates the preferential interaction of water with carbon dioxide relative to methane and decane. Notably, there is an enrichment of the interface by decane at high mole fractions of methane in the methane/decane-rich or methane/carbon dioxide/decane-rich phase. Overall, the solubility of methane and carbon dioxide in the water-rich phase increases with increasing pressure and temperature. Additionally, we find that the overall performance of the PC-SAFT EoS and the cubic-plus-association EoS is similar with respect to the calculation of bulk and interfacial properties of these systems.
  • Metagrating-Based Terahertz Polarization Beam Splitter Designed by Simplified Modal Method

    Ma, Xinyu; Li, Yanfeng; Lu, Yongchang; Han, Jiaguang; Zhang, Xixiang; Zhang, Weili (Frontiers in Physics, Frontiers Media SA, 2020-10-15) [Article]
    Terahertz waves are finding important applications in diverse fields, and meanwhile the manipulation of terahertz waves calls for the development of various functional devices. Here, we have designed and fabricated a metagrating-based polarization beam splitter for terahertz waves using the simplified modal method. By only considering two propagation modes and treating the grating as a Mach-Zehnder interferometer, the method can greatly simplify the reverse grating design process. The parameters of the grating are first obtained under the guidance of the simplified modal method and then improved upon by the finite element method. The fabricated device is finally experimentally demonstrated with a terahertz time-domain spectroscopy system. The diffraction efficiencies of the polarization beam splitter at 0.9 THz are measured to be 69 and 63% for TE and TM waves relative to that of a silicon plate, respectively. The corresponding extinction ratios are 12 and 17 dB for TE and TM waves, respectively. The experiment results agree well with the simulations.
  • Organic carbon export and loss rates in the Red Sea

    Kheireddine, Malika; Dall'Olmo, Giorgio; Ouhssain, Mustapha; Krokos, Georgios; Claustre, Hervé; Schmechtig, Catherine; Poteau, Antoine; Zhan, Peng; Hoteit, Ibrahim; Jones, Burton (Global Biogeochemical Cycles, American Geophysical Union (AGU), 2020-10-14) [Article]
    The export and fate of organic carbon in the mesopelagic zone are still poorly understood and quantified due to lack of observations. We exploited data from a BGC-Argo float that was deployed in the Red Sea to study how a warm and hypoxic environment can affect the fate of the organic carbon in the ocean’s interior. We observed that only 10% of the particulate organic carbon (POC) exported survived at depth due to remineralization processes in the upper mesopelagic zone. We also found that POC exported was rapidly degraded in a first stage and slowly in a second one, which may be dependent on the palatability of the organic matter. We observed that AOU-based loss rates (a proxy of the remineralization of total organic matter) were significantly higher than the POC-based loss rates, likely because changes in AOU are mainly attributed to changes in dissolved organic carbon. Finally, we showed that POC- and AOU-based loss rates could be expressed as a function of temperature and oxygen concentration. These findings advance our understanding of the biological carbon pump and mesopelagic ecosystem.
  • Stability theory of nano-fluid over an exponentially stretching cylindrical surface containing microorganisms.

    Ferdows, M; Hossan, Amran; Bangalee, M Z I; Sun, Shuyu; Alzahrani, Faris (Scientific reports, Springer Science and Business Media LLC, 2020-10-13) [Article]
    This research is emphasized to describe the stability analysis in the form of dual solution of the flow and heat analysis on nanofluid over an exponential stretching cylindrical surface containing microorganisms. The research is also implemented to manifest the dual profiles of velocity, temperature and nanoparticle concentration in the effect of velocity ratio parameter ([Formula: see text]). Living microorganisms' cell are mixed into the nanofluid to neglect the unstable condition of nano type particles. The governing equations are transformed to non-linear ordinary differential equations with respect to pertinent boundary conditions by using similarity transformation. The significant differential equations are solved using build in function bvp4c in MATLAB. It is seen that the solution is not unique for vertical stretching sheet. This research is reached to excellent argument when found results are compared with available result. It is noticed that dual results are obtained demanding on critical value ([Formula: see text]), the meanings are indicated at these critical values both solutions are connected and behind these critical value boundary layer separates thus the solution are not stable.
  • Beryllene: A Promising Anode Material for Na- and K-Ion Batteries with Ultrafast Charge/Discharge and High Specific Capacity

    Sun, Minglei; Yan, Yuan; Schwingenschlögl, Udo (The Journal of Physical Chemistry Letters, American Chemical Society (ACS), 2020-10-12) [Article]
    We predict two-dimensional Be materials, α- and β-beryllene. In α-beryllene each Be atom binds to six other Be atoms in a planar scheme, whereas β-beryllene consists of two stacked α-beryllene monolayers. Both α- and β-beryllene are found to be highly stable, as demonstrated by high cohesive energies close to that of bulk Be, an absence of imaginary phonon modes, and high melting points. Both materials are metallic, indicating potential applications in Na-ion and K-ion batteries, which are explored in detail. The diffusion barriers of Na (K) on α- and β-beryllene are found to be only 9 (3) and 4 (5) meV, respectively. In particular, the diffusion barrier of K on α-beryllene exhibits the lowest ever recorded value in two-dimensional materials, suggesting the possibility of ultrafast charge/discharge. As the theoretical specific capacities of Na/K on α- and β-beryllene are found to be 1487/1322 and 743/743 mA h g–1, respectively, the storage capacity is ultrahigh.
  • Metal Halide Perovskites for High-Energy Radiation Detection

    Kakavelakis, George; Gedda, Murali; Panagiotopoulos, Apostolis; Kymakis, Emmanuel; Anthopoulos, Thomas D.; Petridis, Konstantinos (Advanced Science, Wiley, 2020-10-12) [Article]
    Metal halide perovskites (MHPs) have emerged as a frontrunner semiconductor technology for application in third generation photovoltaics while simultaneously making significant strides in other areas of optoelectronics. Photodetectors are one of the latest additions in an expanding list of applications of this fascinating family of materials. The extensive range of possible inorganic and hybrid perovskites coupled with their processing versatility and ability to convert external stimuli into easily measurable optical/electrical signals makes them an auspicious sensing element even for the high-energy domain of the electromagnetic spectrum. Key to this is the ability of MHPs to accommodate heavy elements while being able to form large, high-quality crystals and polycrystalline layers, making them one of the most promising emerging X-ray and γ-ray detector technologies. Here, the fundamental principles of high-energy radiation detection are reviewed with emphasis on recent progress in the emerging and fascinating field of metal halide perovskite-based X-ray and γ-ray detectors. The review starts with a discussion of the basic principles of high-energy radiation detection with focus on key performance metrics followed by a comprehensive summary of the recent progress in the field of perovskite-based detectors. The article concludes with a discussion of the remaining challenges and future perspectives.
  • The elemental analysis and multi-nuclear NMR study of an alkali molten salt used to digest reference and commercial SWCNT powders

    Simoes, Filipa R. F.; Abou-Hamad, Edy; Kamenik, Jan; Kučera, Jan; Da Costa, Pedro M. F. J. (Journal of Analytical Atomic Spectrometry, Royal Society of Chemistry (RSC), 2020-10-09) [Article]
    For quite some time, alkaline oxidation (or fusion) has been used to solubilize refractory materials and mineral ores. Recently, its application scope was extended to facilitate batch-scale elemental analysis of nanomaterials such as carbon nanotubes. Here, a sodium tetraborate salt was used to digest four different types of single-walled carbon nanotubes. These samples were produced employing Co–Mo or Fe catalyst systems. Their graphitic matrix was exposed to different melt temperatures for a short period of time, following which the concentration of six transition metals was measured. Recoveries in excess of 80% were obtained, with the melt temperature affecting more the elemental extraction in Fe-catalyzed nanotubes. Together with previous results, the work described allows drawing pertinent conclusions on the advantages and limitations of alkaline oxidation as an alternative sample digestion approach for the routine chemical analysis of nanocarbons.
  • Investigating the Catalytic Active Sites of Mo/HZSM-5 and Their Deactivation During Methane Dehydroaromatization

    Wang, Ning; Dong, Xinglong; Liu, Lingmei; Cai, Dali; Wang, Jianjian; Hou, Yilin; Emwas, Abdul-Hamid M.; Gascon, Jorge; Han, Yu (SSRN Electronic Journal, Elsevier BV, 2020-10-09) [Article]
    Molybdenum supported on zeolite HZSM-5 (Mo/HZSM-5) is the most studied catalyst for methane dehydroaromatization (MDA). However, the nature of its catalytic active sites and their deactivation mechanisms remain unclear and controversial. Here we report new insights into this system, on the basis of advanced characterization and a rational design of experiments. We find that it is the size of the HZSM-5 crystal that determines the form and location of the catalytic active molybdenum carbide (MoCx) species, and thus the performance of Mo/HZSM-5; we also find that MoCx sites are preferentially deactivated over acid sites, when supported on nano-sized HZSM-5. These findings lead us to develop an “encapsulation” strategy, which effectively reconciles the deactivation rates at the MoCx sites and the acid sites, enabling a full utilization of both sites, and consequently leading to a 10-fold increase in catalyst lifetime and aromatics yield. Our results indicate that MoCx particles formed outside the micropores of HZSM-5, which are traditionally considered detrimental to the reaction, can serve as active sites for MDA, provided that they are properly protected from direct exposure to coke deposition. These findings allow us to design control experiments to answer an open question whether the acid sites, in addition to promoting the dispersion of Mo species, play a catalytic role in the MDA reaction, and the results show that acid sites are indeed essential for the conversion of methane.
  • Symmetry Breaking in Monometallic Nanocrystals toward Broadband and Direct Electron Transfer Enhanced Plasmonic Photocatalysis

    Shao, Wei; Pan, Qianqian; Chen, Qiaoli; Zhu, Chongzhi; Tao, Weijian; Zhu, Haiming; Song, Huijun; Liu, Xuelu; Tan, Ping-Heng; Sheng, Guan; Sun, Tulai; Li, Xiaonian; Zhu, Yihan (Advanced Functional Materials, Wiley, 2020-10-08) [Article]
    Metallic nanocrystals manifest themselves as fascinating light absorbers for applications in plasmon-enhanced photocatalysis and solar energy harvesting. The essential challenges lie in harvesting the full-spectrum solar light and harnessing the plasmon-induced hot carriers at the metal–acceptor interface. To this end, a cooperative overpotential and underpotential deposition strategy is proposed to mitigate both the challenges. Specifically, by utilizing both ionic additive and thiol passivator to introduce symmetry-breaking growth over gold icosahedral nanocrystals, the microscopic origin can be attributed to the site-specific nucleation of stacking faults and dislocations. By adopting asymmetric crystal shape and unique surface facets, such nanocrystals attain high activity toward photocatalytic ammonia borane hydrolysis, arising from combined broadband plasmonic properties and enhanced direct transfer of hot electrons across the metal–adsorbate interface.
  • Laser induced fluorescence investigation of the chemical impact of nanosecond repetitively pulsed glow discharges on a laminar methane-air flame

    Del Cont-Bernard, Davide; Guiberti, Thibault; Lacoste, Deanna (Proceedings of the Combustion Institute, Elsevier BV, 2020-10-08) [Article]
    This paper reports on an experimental investigation of the chemical impact of nanosecond repetitively pulsed (NRP) glow discharges on a laminar methane-air flame. The chosen configuration was a lean wall stabilized flame where NRP discharges were generated across the flame front. After careful selection of the excitation lines, planar laser induced fluorescence of OH and CH was conducted. Comparisons between the OH and CH fluorescence of a base flame (without plasma actuation), and those obtained during the steady state and the transient regimes of plasma actuation, were performed. First it is shown that during the steady state regime, the intensity of OH and CH fluorescence in the flame could be increased by up to 40% and 10%, respectively. In addition, the life time of OH fluorescence in the discharge channel was estimated to be between 3 and 4.5 µs. The transient regime at the beginning of plasma actuation showed that the flame began to be affected by the discharges long before OH fluorescence could be detected in the discharge channel, upstream of the flame. After 40 ms of plasma actuation, OH intensity began to increase simultaneously in both the flame and the discharge area. Based on current knowledge of nanosecond discharge chemistry, explanations for these results are proposed.
  • Diels-Alder Polymer Networks with Temperature-Reversible Cross-Linking-Induced Emission Yu Jiang*, and Nikos Hadjichristidis*

    Hadjichristidis, Nikos; Jiang, Yu (Angewandte Chemie, Wiley, 2020-10-08) [Article]
    A novel synthetic strategy toward reversible cross-linked polymeric materials with tunable fluorescence properties is presented. Dimaleimide-substituted tetraphenylethene (TPE-2MI), which is nonemissive due to the photo-induced electron transfer (PET) between maleimide (MI) and tetraphenylethene (TPE) groups, was used to cross-link random copolymers of methyl (MM), decyl (DM) or lauryl (LM) with furfuryl methacrylate (FM). The mixture of copolymer and TPE-2MI in DMF showed reversible fluorescence with “on/off” behavior depending on the Diels-Alder (DA)/retro-DA process, which is easily adjusted by temperature. At high temperatures, the retro-DA reaction of polymer networks is dominant, and the fluorescence is quenched by the PET mechanism. In contrast, at low temperatures, the emission recovers as the DA reaction takes over. Based on these results, a transparent PMFM/TPE-2MI film was prepared, and the emission behavior was investigated. It was found that the polymer film shows an accurate response to the external temperature and exhibited tunable fluorescent “turn on/off” behavior. These excitingresults suggest the possible application of this type of reversible cross-linked materials in many areas, including information security and transmission. An example of invisible/visible writing is given.
  • Multitude of dimple shapes can produce singular jets during the collapse of immiscible drop-impact craters

    Yang, Zi Qiang; Tian, Yuansi; Thoroddsen, Sigurdur T (Journal of Fluid Mechanics, Cambridge University Press (CUP), 2020-10-07) [Article]
    We study singular jets from the collapse of drop-impact craters, when the drop and pool are of different immiscible liquids. The fastest jets emerge from a dimple at the bottom of the rebounding crater, when no bubble is pinched off. The parameter space is considerably more complex than for identical liquids, revealing intricate compound-dimple shapes. In contrast to the universal capillary–inertial drop pinch-off regime, where the neck radius scales as R ∼ t 2/3, for a purely inertial air dimple the collapse has R ∼ t 1/2. The bottom dimple dynamics is not self-similar but possesses memory effects, being sensitive to initial and boundary conditions. Sequence of capillary waves can therefore mould the air dimple into different collapse shapes, such as bamboo-like and telescopic forms. The finest jets are only 12 μm in diameter and the normalized jetting speeds are up to one order of magnitude larger than for jets from bursting bubbles. We study the cross-over between the two power laws approaching the singularity. The singular jets show the earliest cross-over into the inertial regime. The fastest jets can pinch off a toroidal micro-bubble from the cusp at the base of the jet.
  • In silico design of novel NRR electrocatalysts: cobalt-molybdenum alloys.

    Castellano-Varona, Blanca; Harb, Moussab; Araña, Javier; Cavallo, Luigi; Azofra Mesa, Luis (Chemical communications (Cambridge, England), Royal Society of Chemistry (RSC), 2020-10-07) [Article]
    Metals are amongst the most efficient developed electrocatalysts for nitrogen reduction reaction (NRR) with iron and ruthenium presenting the best catalytic indicators. However, the potential use of metal alloys as NRR electrocatalysts is still underdeveloped. While Co has demonstrated poor electrocatalytic activity for NRR, alloying Co with Mo exhibits an improvement in both N2 physisorption and the stabilisation of the elusive N2H as the first reduced intermediate species. This stabilisation occurs on surface Mo or Co atoms with a high connectivity with Mo. Herein, we report a complete DFT study analysing the potential application of CoMo alloys as catalysts for N2-into-NH3 conversion given the low theoretical overpotentials that they present.
  • Optical frequency metrology in the bending modes region

    Lamperti, Marco; Gotti, Riccardo; Gatti, Davide; Shakfa, Mohammad Khaled; Cané, E.; Tamassia, F.; Schunemann, P.; Laporta, P.; Farooq, Aamir; Marangoni, M. (Communications Physics, Springer Science and Business Media LLC, 2020-10-06) [Article]
    Abstract Optical metrology and high-resolution spectroscopy, despite impressive progress across diverse regions of the electromagnetic spectrum from ultraviolet to terahertz frequencies, are still severely limited in the region of vibrational bending modes from 13 to 20 µm. This long-wavelength part of the mid-infrared range remains largely unexplored due to the lack of tunable single-mode lasers. Here, we demonstrate bending modes frequency metrology in this region by employing a continuous-wave nonlinear laser source with tunability from 12.1 to 14.8 µm, optical power up to 110 µW, MHz-level linewidth and comb calibration. We assess several CO2-based frequency benchmarks with uncertainties down to 30 kHz and we provide an extensive study of the v11 band of benzene, a significant testbed for the resolution of the spectrometer. These achievements pave the way for long-wavelength infrared metrology, rotationally-resolved studies and astronomic observations of large molecules such as aromatic hydrocarbons.
  • Sunlight-Driven Biomass Photorefinery for Coproduction of Sustainable Hydrogen and Value-Added Biochemicals

    Wu, Xinxing; Zhao, Heng; Khan, Mohd Adnan; Maity, Partha; Al-Attas, Tareq; Larter, Stephen; Yong, Qiang; Mohammed, Omar F.; Kibria, Md Golam; Hu, Jinguang (ACS Sustainable Chemistry & Engineering, American Chemical Society (ACS), 2020-10-06) [Article]
    We demonstrate a potential pathway of biomass photorefinery (PR) using low-cost CoO/g-C3N4 catalysts for the coproduction of hydrogen and lactic acid under visible light illumination. To do so, we follow a bottom-up approach to systematically investigate the photoreforming performance of glucose, different model celluloses (cellulose I and mercerized and regenerated cellulose II), and raw biomass. Under optimized conditions, the glucose was totally consumed within 3 h of reaction, with nearly 78 wt % carbon conversion to lactic acid. The highest activity observed for cellulose in the PR used phosphoric acid swollen cellulose (PASC, regenerated cellulose II) with a H2 production rate of ∼178 μmol·h−1·gcat−1 , more than 71 wt % cellulose conversion after 12 h, and the formation of ∼617 μmol lactic acid per gram of cellulose. This high activity was mainly attributed to enhanced interaction of the photocatalyst with PASC, as evidenced by quartz crystal microbalance analysis. Based on the knowledge obtained from model cellulose, we took a step further to evaluate the photorefining ability of raw lignocellulosic biomass wheat straw (WS), with/without various biomass pretreatment strategies. The pretreated biomass showed much higher H2 and lactic acid production and cellulose conversions as compared with raw biomass but the degree of improvement is highly dependent on pretreatment strategies. Our results not only demonstrate the potential of using visible light for the coproduction of H2, along with value-added bioproducts from biomass PR, but also shed light on developing pretreatment strategies to achieve a scalable biomass PR.
  • Cyclized polyacrylonitrile anode for alkali metal ion batteries

    Zhang, Wenli; Sun, Minglei; Yin, Jian; Abou-Hamad, Edy; Schwingenschlögl, Udo; Da Costa, Pedro M. F. J.; Alshareef, Husam N. (Angewandte Chemie International Edition, Wiley, 2020-10-05) [Article]
    Alkali metal (Li, Na, and K) ion batteries are vital in portable and large-scale stationary energy storage. Recently, organic anodes have attracted increasing attention for alkali metal ion batteries due to their chemical diversity and potential high capacity. In this work, we discovered that cyclized polyacrylonitrile (cPAN) can serve as a superior anode for alkali metal ion batteries. Remarkably, upon activation cycling, as an anode of lithium-ion battery, cPAN exhibits a reversible capacity as high as 1238 mAh g-1 under a current density of 50 mA g-1. Based on electrochemical experiments and first-principles calculations, it is demonstrated that the hexagonal carbon ring, piperidine ring, and pyridine nitrogen in ladder cPAN are the main active sites for lithium-ion storage. In addition, we show that cPAN displays a unique potential-dependent solid electrolyte interphase formation from 0.1 to 0.01 V vs. Li/Li+. Furthermore, cPAN displays decent performance as an anode in SIBs and PIBs. The discovery of cPAN anode could pave the way for the future development of organic anodes for alkali metal ion batteries.
  • Cyclized polyacrylonitrile anode for alkali metal ion batteries

    Zhang, Wenli; Sun, Minglei; Yin, Jian; Abou-Hamad, Edy; Schwingenschlögl, Udo; Da Costa, Pedro M. F. J.; Alshareef, Husam N. (Angewandte Chemie International Edition, Wiley, 2020-10-05) [Article]
    Alkali metal (Li, Na, and K) ion batteries are vital in portable and large-scale stationary energy storage. Recently, organic anodes have attracted increasing attention for alkali metal ion batteries due to their chemical diversity and potential high capacity. In this work, we discovered that cyclized polyacrylonitrile (cPAN) can serve as a superior anode for alkali metal ion batteries. Remarkably, upon activation cycling, as an anode of lithium-ion battery, cPAN exhibits a reversible capacity as high as 1238 mAh g-1 under a current density of 50 mA g-1. Based on electrochemical experiments and first-principles calculations, it is demonstrated that the hexagonal carbon ring, piperidine ring, and pyridine nitrogen in ladder cPAN are the main active sites for lithium-ion storage. In addition, we show that cPAN displays a unique potential-dependent solid electrolyte interphase formation from 0.1 to 0.01 V vs. Li/Li+. Furthermore, cPAN displays decent performance as an anode in SIBs and PIBs. The discovery of cPAN anode could pave the way for the future development of organic anodes for alkali metal ion batteries.
  • Titanium methyl tamed on silica: synthesis of a well-defined pre-catalyst for hydrogenolysis of n-alkane

    Saidi, Aya; Almaksoud, Walid; Samantaray, Manoja K.; Abou-Hamad, Edy; Basset, Jean-Marie (Chemical Communications, Royal Society of Chemistry (RSC), 2020-10-05) [Article]
    Alkylation of Ti(CH3)2Cl2 1 by MeLi gives the homoleptic Ti(CH3)42 for the first time in the absence of any coordinating solvent. The reaction of 2 with silica pretreated at 700 8C (SiO2–700) gives two inequivalent silica-supported Ti-methyl species 3. Complex 3 was characterized by IR, microanalysis (ICP-OES, CHNS, and gas quantification), and advanced solid-state NMR spectroscopy (1H, 13C, DQ, TQ, and HETCOR). The catalytic activity of the precatalyst 3 is investigated in low-temperature hydrogenolysis of propane and n-butane with TONs of 419 and 578, respectively
  • Gas-sieving zeolitic membranes fabricated by condensation of precursor nanosheets

    Dakhchoune, Mostapha; Villalobos, Luis Francisco; Semino, Rocio; Liu, L. M.; Rezaei, Mojtaba; Schouwink, Pascal; Avalos, Claudia Esther; Baade, Paul; Wood, Vanessa; Han, Yu; Ceriotti, Michele; Agrawal, Kumar Varoon (Nature Materials, Springer Science and Business Media LLC, 2020-10-05) [Article]
    The synthesis of molecular-sieving zeolitic membranes by the assembly of building blocks, avoiding the hydrothermal treatment, is highly desired to improve reproducibility and scalability. Here we report exfoliation of the sodalite precursor RUB-15 into crystalline 0.8-nm-thick nanosheets, that host hydrogen-sieving six-membered rings (6-MRs) of SiO4 tetrahedra. Thin films, fabricated by the filtration of a suspension of exfoliated nanosheets, possess two transport pathways: 6-MR apertures and intersheet gaps. The latter were found to dominate the gas transport and yielded a molecular cutoff of 3.6 Å with a H2/N2 selectivity above 20. The gaps were successfully removed by the condensation of the terminal silanol groups of RUB-15 to yield H2/CO2 selectivities up to 100. The high selectivity was exclusively from the transport across 6-MR, which was confirmed by a good agreement between the experimentally determined apparent activation energy of H2 and that computed by ab initio calculations. The scalable fabrication and the attractive sieving performance at 250–300 °C make these membranes promising for precombustion carbon capture.

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