Search

Beckmann rearrangement of three kinds of oximes to lactams on MFI zeolite nanosheets was investigated to elucidate the catalytic reaction sites, silanols.

Mesoporous zeolite-supported Pt3Y catalyst deactivates slowly in propane dehydrogenation, maintaining high propane conversion and propylene selectivity, but the formation of the intermetallic compound requires atomistic migration of yttrium through silanol nests on the zeolite. Compared to the cumbersome generation of silanols via framework demetallation, we report a direct synthesis of mesoporous MFI zeolite possessing silanol nests. The synthesis procedure employed a diammonium-type bromide surfactant [C18H37 N(CH3)2 C6H12 N(CH3)2 C4H9Br2] and a sodium-free silica source. The basicity of the synthesis mixture was adjusted by the addition of readily available N(CH3)4OH, instead of converting the surfactant to hydroxyl form. The presence of silanol nests in the resultant zeolite was confirmed by IR and NMR spectroscopies. When the zeolite was supported with 0.50 wt% Pt and 0.50 wt% Y using nitrate precursors, a remarkably long catalytic lifetime of 20 days was obtained with high propane conversion and propylene selectivity under the reaction condition using neat propane gas at 853 K.

An elastic printed circuit board (E-PCB) is a conductive framework used for the facile assembly of system-level stretchable electronics. E-PCBs require elastic conductors that have high conductivity, high stretchability, tough adhesion to various components, and imperceptible resistance changes even under large strain. We present a liquid metal particle network (LMP Net ) assembled by applying an acoustic field to a solid-state insulating liquid metal particle composite as the elastic conductor. The LMP Net conductor satisfies all the aforementioned requirements and enables the fabrication of a multilayered high-density E-PCB, in which numerous electronic components are intimately integrated to create highly stretchable skin electronics. Furthermore, we could generate the LMP Net in various polymer matrices, including hydrogels, self-healing elastomers, and photoresists, thus showing their potential for use in soft electronics.

A PtZn alloy nanoparticle catalyst for propane dehydrogenation was synthesized by simple coimpregnation of Pt(NH3)4(NO3)2 with Zn(NO3)2 onto a mesoporous material, which was built with siliceous MF...

Coronene and its derivatives were synthesized using methanol inside Ca2+ ion-exchanged small-pore zeolites with an 8-membered ring window, such as LTA and RHO zeolites. The polyaromatic hydrocarbon product exhibited white fluorescence under UV light excitation, as characterized by UV-Vis absorption and fluorescence spectra, and fluorescence microscopy images. The formation of coronene and even larger polyaromatics from methanol could be attributed to the fact that Ca2+ ions, unlike the hydroxyl protons of acidic zeolite frameworks, effectively attract the π-electron clouds of benzene rings of small polycyclic intermediates with no disruption of the aromaticity, which leads to the rapid growth of the aromatic ring system. The molecular dimensions of the resultant polyaromatic product were determined by the confined α-cages of the LTA and RHO zeolites. This phenomenon could be extended to CHA zeolite with smaller pore sizes, restricting the molecular growth more severely than in the cases of LTA and RHO zeolites.

Platinum is a much used catalyst that, in petrochemical processes, is often alloyed with other metals to improve catalytic activity, selectivity and longevity1-5. Such catalysts are usually prepared in the form of metallic nanoparticles supported on porous solids, and their production involves reducing metal precursor compounds under a H2 flow at high temperatures6. The method works well when using easily reducible late transition metals, but Pt alloy formation with rare-earth elements through the H2 reduction route is almost impossible owing to the low chemical potential of rare-earth element oxides6. Here we use as support a mesoporous zeolite that has pore walls with surface framework defects (called 'silanol nests') and show that the zeolite enables alloy formation between Pt and rare-earth elements. We find that the silanol nests enable the rare-earth elements to exist as single atomic species with a substantially higher chemical potential compared with that of the bulk oxide, making it possible for them to diffuse onto Pt. High-resolution transmission electron microscopy and hydrogen chemisorption measurements indicate that the resultant bimetallic nanoparticles supported on the mesoporous zeolite are intermetallic compounds, which we find to be stable, highly active and selective catalysts for the propane dehydrogenation reaction. When used with late transition metals, the same preparation strategy produces Pt alloy catalysts that incorporate an unusually large amount of the second metal and, in the case of the PtCo alloy, show high catalytic activity and selectivity in the preferential oxidation of carbon monoxide in H2.

The authors have requested that this preprint be removed from Research Square.

Zeolite-templated synthesis is a versatile route to ordered microporous carbons built with single-walled sp2 framework of various structures, but the use of hazardous HF to dissolve the zeolite template is still a critical safety issue. We investigated the template-removal process using NaOH and HCl, which are safer than HF. The results indicated that the residual ash content in the carbon could be lowered to less than 5 wt% when the template was removed by consecutive treatments using NaOH and HCl in a proper sequence depending on the zeolite framework type. The carbon obtained in this manner exhibited a rather increased supercapacitance in aqueous media at high current density, as compared to carbons from HF-washing. In the case of the non-aqueous supercapacitor, however, the washing with NaOH–HCl resulted in low capacitance. This was due to the effect of NaOH to generate oxygen-functional groups, which could lead to an increase in the hydrophilicity, and a decrease in the electrical conductivity. Furthermore, the oxygen-functional groups could serve as a base to graft organic amines. When the carbon was heated in H2, the oxygen content decreased to a similar level to that of the HF-washed carbon, restoring the conductivity and electrochemical energy storage characteristics.

Sulfur-centered phenyl, n-butyl, p-tolyl, and benzyl sulfoniums and sulfides were tested as organic structure-directing agents (SDAs) for the synthesis of crystalline microporous aluminophosphates (AlPOs) over various ranges of gel compositions, hydrothermal treatment temperatures, and crystallization times. Among the investigated compounds, triphenylsulfonium gave single-phase products of ATS-type AlPO and silicoaluminophosphate. Other sulfoniums yielded only non-porous, dense crystalline AlPOs. On the other hand, diaryl sulfides gave a tiny amount of AFI-type AlPO amid tridymite and amorphous phases. Based on the results, it was found to be reasonable that weakly basic sulfide could hardly act as a zeotype SDA due to the low protonation to sulfonium at the present synthesis pH.

Zinc–air batteries (ZnABs) are among the most promising energy storage devices, offering multiple advantages of high energy density, low manufacturing cost, high safety, and environmental benignity. However, challenges remain in the development of ZnAB electrode materials due to the lack of efficient air-electrode catalysts for solving the problems regarding slow kinetics of the oxygen reduction/evolution reactions (ORR/OER) and poor durability. Here, we report the formation of Co3O4 nanosheets with rich oxygen-vacancy defects grown on zeolite-templated carbon (ZTC) for electrocatalytic application in a ZnAB. Hydrophobic ZTC serves as a substrate for the growth of the Co3O4 nanosheets. Oxygen vacancies are generated by the borohydride reduction of Co2+, followed by oxidation with oxygen in atmospheric air. The resultant oxygen-vacancy defective Co3O4 nanosheets on ZTC (Co3O4 NS/ZTC) exhibits excellent bifunctional electrocatalytic activity towards the ORR/OER and high durability, compared with commercial Pt/C and RuO2 catalysts. The high bifunctional electrocatalytic activity is attributed to the sheet-like structure and oxygen-vacancy defects of Co3O4 and the high surface area and uniform microporosity of ZTC. The ZnAB with the bifunctional electrocatalyst exhibits excellent discharge performance and long-term charge/discharge cycling stability.

The formation of highly dispersed Pt nanoclusters supported on zeolite-templated carbon (PtNC/ZTC) by a facile electrochemical method as an electrocatalyst for the oxygen reduction reaction (ORR) is reported. The uniform micropores of ZTC serve as nanocages to stabilize the PtNCs with a sharp size distribution of 0.8–1.5 nm. The resultant PtNC/ZTC exhibits excellent catalytic activity for the ORR due to the small size of the Pt clusters and high accessibility of the active sites through the abundant micropores in ZTC.

Microporous 3D graphene-like carbons were synthesized in Faujasite (FAU)-, EMT-, and beta-zeolite templates using the recently developed Ca2+ ion-catalyzed synthesis method. The microporous carbons liberated from these large-pore zeolites (0.7-0.9 nm) retain the structural regularity of zeolite. FAU-, EMT-, and beta zeolite-templated carbons (ZTCs) with faithfully constructed pore diameters of 1.2, 1.1, and 0.9 nm, respectively, and very large Brunauer-Emmet-Teller areas (2700-3200 m2 g-1) were obtained. We have discovered that these schwarzite-like carbons exhibit preferential adsorption of ethane over ethylene at pressures in the range of 1-10 bar. The curved graphene structure, consisting of a diverse range of carbon polygons with a narrow pore size of ∼1 nm, provides abundant adsorption sites in micropores and retains its ethane selectivity at pressures up to 10 bar. After varying the oxygen content in the beta ZTC, the ethane and ethylene adsorption isotherms show that the separation ability is not significantly affected by surface oxygen groups. Based on these adsorption results, a breakthrough separation procedure using a C2H4/C2H6 gas mixture (9:1 molar ratio) is demonstrated to produce ethylene with a purity of 99.9%.

Polycyclic aromatic hydrocarbons (PAHs) attract much attention for applications to organic light-emitting diodes, field-effect transistors, and photovoltaic cells. The current synthetic approaches to PAHs involve high-temperature flash pyrolysis or complicated step-by-step organic reactions, which lead to low yields of PAHs. Herein, we report a facile and scalable synthesis of PAHs, which is carried out simply by flowing acetylene gas into zeolite under mild heating, typically at 400 °C and generates the products of 0.30 g g–1 zeolite. PAHs are synthesized via acetylene polymerization inside Ca2+-ion-exchanged Linde type A (LTA) zeolite, of which the α-cage puts a limit on the product molecular size as a confined-space nanoreactor. The resultant product after the removal of the zeolite framework exhibits brilliant white fluorescence emission in N-methylpyrrolidone solution. The product is separated into four different color emitters (violet, blue, green, and orange) by column chromatography. Detailed char...

Zeolite-templated carbon, having a three-dimensional graphene-like ordered microporous structure with high electrical conductivity, is a fascinating anode material for Li-ion batteries (LIBs). Herein, we report an extremely high Li capacity of 2950 mA h g–1 (equivalent to Li1.3/C), which is 7.9 times the maximum capacity of graphite, Li/C6. This is equivalent to the crowded packing of 20 Li+ per pore with 0.9 nm diameter. Approximately 59% of the capacity was reversible. According to the characterizations by electron energy loss spectroscopy, 7Li NMR, and 13C NMR, most of the Li species existed as Li+ within the carbon micropores. Contrary to the often-made assumption, only a small amount of solid–electrolyte interphase layers was detected at the external surface of the carbon particles but not inside the micropores. The anomalously high Li capacity is attributed to the extremely narrow pore environment, where Li+ would be difficult to be fully solvated. Tailoring of the carbon pores to a subnanometric ra...

Zinc (Zn)‐based aqueous battery‐supercapacitor hybrid (BSH) devices are considered promising energy storage devices benefiting from their high energy and power densities, low‐cost, safety, and environmental benignity. However, challenges remain in the development of efficient BSH electrodes due to poor reversibility in battery electrodes and lack of efficient supercapacitor electrodes to solve the problems of low power and energy densities. Herein, the loading of iodine (I2) in the nanopores of 3D graphene‐like carbon (3DGC) for the fabrication of BSH electrodes and their device application with Zn are reported. The uniform micropores of 3DGC serve as nanocages to stabilize I2, the high surface area of 3DGC maximizes the dispersion, and the high conductivity of 3DGC provides a path for fast electron transfer. The resultant I2‐loaded 3DGC (I2/3DGC) is applied to evaluate Zn‐based battery and BSH performance. The I2/3DGC‐based electrode exhibits excellent performance with ultrahigh energy and power densities resulting from the high reversibility of I2 and supercapacitance of 3DGC. The device exhibits high cyclic stability in both battery and supercapacitor modes due to the confinement of I2 in the micropores. It is demonstrated that this combination of 3DGC with I2 provides an easy way to fabricate durable and economical BSH electrodes.

Platinum is a much used catalyst that, in petrochemical processes, is often alloyed with other metals to improve catalytic activity, selectivity and longevity

In this work, role of phase composition and interstitial oxygen on the thermoelectric properties of CuCr0.85Mg0.15O2 materials prepared at different sintering temperatures (1273–1673 K) for short time (3 h) are reported. Interestingly, the samples sintered at 1273 K and 1673 K had the same Seebeck coefficient, despite the 1273 K sample having significantly lower conductivity, which are discussed via phase composition and interstitial oxygen induced during the CuCrO2 phase formation and its related defect (VCu, VCr, …). Besides, high conductivity of the 1673 K sample originated from the low percentage of CuO phase and the appearance of Cu2O phase. Since the 1273 K and 1673 K sintered samples have almost the same percentage of delafossite and spinel phases so the 1673 K sample still remain its high Seebeck coefficient. We suggest some reaction chemical equations for elucidating the roles of interstitial oxygen on the phase composition and thermoelectric properties CuCr0.85Mg0.15O2 delafossite material.

Zeolite-templated synthesis of ordered microporous carbons was performed with Ca2+ ion-exchanged Y and beta zeolites, where the conventionally used carbon source gases (e.g., ethylene and propylene) were replaced by various organic solvents, such as methanol, ethanol, isopropanol, acetone, tetrahydrofuran, and diisopropyl ether. The oxygen-containing solvents were fed to the zeolites as carried by N2 gas through a bubbler. Mass spectrometric analyses of the carbonization stream indicated that isopropanol, acetone, tetrahydrofuran, and diisopropyl ether were converted largely to propylene and H2O vapor, while ethanol and methanol to ethylene. The simultaneous generation of H2O and the olefins, without using high-pressure gas cylinders, can be merit in the Ca2+ ion-catalyzed synthesis of zeolite-templated carbons (ZTCs). The approach in this work provides a facile way to produce high quality ZTCs exhibiting excellent micropore orders and high specific capacitances in supercapacitor applications.

The thermoelectric performance of CuCr1-xMgxO2 materials in terms of multi-scale defects induced at various Mg dopant concentrations (x = 0–0.3) was thoroughly studied in this paper. At 748 K and for x = 0.05, 0.15, and 0.30, we report the following power factors and thermal conductivities: 175, 213, and 2.3 μW/m K2 and 7.85, 5.60, and 3.82 W/m K, respectively. In the low doping regime (x

A lot of people were trapped in elevators without power supply when BLACK-OUT situation occurred in 2011. The telephone network of control room connected to the elevators had problem operating poorly. In this paper we propose an ICT based elevator emergency call device prototype system and evaluate the performance of the system. The proposed system quickly responds in emergency situation to guarantee passenger safety. For the goal, firstly the system tries to connect to a control room. If it fails the system attempts to call numbers for emergency contact and a rescue team sequentially. The system is designed to quickly support emergency contact as well. Finally, the information of elevator failure is rapidly transferred to the failure process device by the proposed system.

Zeolite Y is widely used as an industrial catalyst for catalytic cracking of heavy feedstocks to lighter olefins. However, incorporation of uniform mesoporosity in zeolite Y without compromising the microporous characteristics is required to improve the catalyst efficiency and minimize catalyst deactivation. Here, we report a facile synthesis method for mesoporous zeolite Y (MPY sg ) using seed gel and amphiphilic organosilane, that results in mesoporous zeolite showing a narrow mesopore size distribution (3–4 nm) with high external surface area (110 m 2 g -1 ) and high micropore surface area (654 m 2 g -1 ). During the crystallization of MPY sg , the organosilane acted as a mesopore-generating agent, and the seed gel provided secondary nuclei that created a uniform mesoporous structure in the zeolite Y nanocrystals. Analysis of aluminosilicate precursors collected during the crystallization revealed that the crystallization process starts with a long nucleation period, followed by rapid crystal growth. Due to the highly accessible strong acid sites present on its external surface, MPY sg shows catalytic activity in the decalin cracking reaction higher than that of conventional microporous zeolite Y.

Nanostructured carbons with high porosity are of great interest as high-performance anode materials for lithium-ion battery (LIB) applications. In the present work, we investigated the Li storage behavior of three-dimensional graphene-like ordered microporous carbon, which was synthesized via a zeolite-templating route. The microporous carbon exhibited an extremely high initial Li storage capacity as an anode for LIBs. Approximately 60% of the initial capacity was reversible during the subsequent cycles, while 40% was irreversible. The reversible capacity was comparable to the highest value reported so far with carbon alone. In order to investigate the chemical state of the Li species (i.e., ionic or metallic), the charged and discharged zeolite-templated carbon sample was characterized with 7Li nuclear magnetic resonance spectroscopy. The location of lithium was investigated using a transmission electron microscope equipped with an electron energy loss spectrometer and an energy-dispersive X-ray spectrometer. The result indicated that most of the reversible and irreversible lithium existed in nonmetallic +1 oxidation state inside the carbon micropores. The huge amount of Li storage is attributed to the three-dimensionally ordered microporous structure with a large surface area built with the single-layer graphene-like framework. In this study, we provides insights on the Li storage behavior in narrow carbon pore environment.

Over the last few years, extensive research efforts have focused on development of solid-state white-light-emitting materials because of their potential for energy-efficient illumination. Common approaches to generate white light emission are either by properly mixing red, green, and blue-emitting semiconductor quantum dots or integrating them with traditional organic phosphors. However, semiconductor nanocrystals containing Cd or other heavy metals have serious toxicity as well as high costs, which considerably limits their practical applications. In recent years, compared to the quantum dots, carbon-based fluorescent nanodots including carbon dots and graphene quantum dots have emerged as promising substitutes for the present fluorescent nanomaterials because of their competitive optical performance - high photostability, non-blinking photoluminescence and versatile tunability of optical properties. Herein we report on a facile synthesis of carbon dot species from acetylene using Ca2+ ion catalyst in zeolite template. The resulting product directly exhibits strong white-fluorescence in N-methyl-2-pyrrolidone (NMP) solution under a single wavelength excitation. The photoluminescence quantum yield of the white emission was determined to be 13.7 % under 340 nm excitation in NMP solution. The current synthesis method is a reliable low-cost synthetic technique, rendering potential various scientific and industrial applications. Figure 1