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Joonil Cho, Yasuhiro Ishida
Porous materials with molecular-sized periodic structures, as exemplified by zeolites, metal-organic frameworks, or mesoporous silica, have attracted increasing attention due to their range of applications in storage, sensing, separation, and transformation of small molecules. Although the components of such porous materials have a tendency to pack in unidirectionally oriented periodic structures, such ideal types of packing cannot continue indefinitely, generally ceasing when they reach a micrometer scale...
April 27, 2017: Advanced Materials
Bing Ma, Huimei Cui, Darui Wang, Peng Wu, Chen Zhao
Ni based catalysts are wildly used in catalytic industrial processes due to their low costs and high activities. The design of highly hierarchical core-shell structured Ni/HBEA is achieved using a sustainable, simple, and easy-tunable hydrothermal synthesis approach using combined NH4Cl and NH3·H2O as a co-precipitation agent at 120 °C. Starting from a single-crystalline hierarchical H(+)-exchanged beta polymorph zeolite (HBEA), the adjustment of the precipitate conditions shows that mixed NH4Cl and NH3·H2O precipitates with proper concentrations are vital in the hydrothermal synthesis for preserving a good crystalline morphology of HBEA and generating abundant highly-dispersed Ni nanoparticles (loading: 41 wt%, 5...
April 25, 2017: Nanoscale
Lichen Liu, Urbano Díaz, Raul Arenal, Giovanni Agostini, Patricia Concepción, Avelino Corma
No abstract text is available yet for this article.
April 25, 2017: Nature Materials
Guo-Yu Yang, Qi Wei, Shi-Jia Sun, Jie Zhang
Two novel alkali/alkaline-earth borates, Ba6[B6O9 (OH)6]2(H3BO3) (1) and Li7MAlB12O24 (M = Ba, Sr, Ca) (2a-c), with 1- and 3-D structures have been hydrothermally made and characterized. 1 features a rarely 1-D anionic chain built by hexaborate clusters of B6O11(OH)6 made of six BO4/ BO2(OH)2 tetrahedra. The anionic chains are embedded in the channels of Ba6-based wheel cluster open-framework. On the basis of the structural analyses of 1, by incorporating the rational Al atoms as the linkers and tuning the reaction conditions, the anhydrous borates 2a-c have been success-fully obtained, showing novel 3-D aluminoborates (ABOs) constructed from B6O14-based cluster chains and AlO6 octa-hedra...
April 24, 2017: Chemistry: a European Journal
X X Zhou, H Zhao, W M Huang, H R Chen, J L Shi
TiO2 and spinel Cu1.5Mn1.5O4 co-modified hierarchically porous zeolite Beta (Ti/Cu1.5Mn1.5O4-HBeta) with 3D interpenetrating micro-mesoporosity has been synthesized, which showed highly efficient catalytic activity to the soot oxidation in the presence of O2/NO/N2 due to the rich moderate intensity acidic sites and chemisorbed oxygen species. In the presence of SO2/O2/NO/N2, the SO2 could be preferentially adsorbed on the Ti/Cu1.5Mn1.5O4-HBeta and the resulting sulfates could easily decompose at elevated temperatures, thus leading to significantly improved sulfur-resistance...
April 24, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Sylvian Cadars, Nak Ho Ahn, Kirill Okhotnikov, Jiho Shin, Aurélie Vicente, Suk Bong Hong, Christian Fernandez
Atomic substitutions are a central feature of the physicochemical properties of an increasing number of solid-state materials. The complexity that this chemical disorder locally generates in otherwise crystalline solids poses a major challenge to the understanding of the relationships between the structure and properties of materials at the atomic and molecular level. Strategies designed to efficiently explore the ensemble of local chemical environments present in disordered crystals and predict their signatures in local spectroscopies such as solid-state nuclear magnetic resonance (NMR) are therefore essential...
April 13, 2017: Solid State Nuclear Magnetic Resonance
Samar Kumar Das, Suranjana Bose, Joyashish Debgupta, Rani Ramsundar
The design and synthesis of an efficient and robust water oxidation catalyst (WOC) with inexpensive materials remain an important challenge in the context of 'artificial photosynthesis'. Herein, we report a simple but unique technique to generate in situ a thin-film of α-Co(OH)2 on the surface of zeolite-Y [hereafter named as Y-α-Co(OH)2] that acts as an efficient and stable catalyst for electrochemical water oxidation in an alkaline pH. Catalyst Y-α-Co(OH)2 is so stable that it retains its catalytic activity even after 2000 cyclic voltammetric cycles of water oxidation...
April 21, 2017: Chemistry: a European Journal
Pfano Mathews Nekhunguni, Nikita Tawanda Tavengwa, Hlanganani Tutu
In this work, the synthesis of iron (hydr) oxide modified zeolite was achieved through precipitation of iron on the zeolite. The structure and surface morphology of iron (hydr) oxide modified zeolite (IHOMZ) was studied by scanning electron microscopy (SEM), coupled with an energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared (FT-IR) spectra. The efficiency of IHOMZ was then investigated through batch technique for the extraction of As(V) from mine waste water. The optimum parameters for maximum As(V) adsorption were: an initial As(V) concentration (10 mg L(-1)), adsorbent dosage (3...
April 15, 2017: Journal of Environmental Management
Zhuo Wang, Tingting Yan, Liyi Shi, Dengsong Zhang
The pores of dodecahedron-like carbon frameworks derived from metal-organic frameworks (MOFs) were in situ expanded via a surfactant-template strategy, which were originally demonstrated to enhance capacitive deionization (CDI). The dodecahedron-like carbon frameworks were obtained through carbonization of zeolitic imidazolate framework-8 (ZIF-8) using the cetyltrimethylammonium bromide as a supramolecular template. It is found that the dodecahedron-like carbon frameworks derived from ZIF-8 possess efficiently expanded pores while retaining the original morphology and high nitrogen contents...
April 21, 2017: ACS Applied Materials & Interfaces
Lingqian Meng, Xiaochun Zhu, Emiel J M Hensen
Fe/ZSM-5 nanosheet zeolites of varying thickness were synthesized with di- and tetraquaternary ammonium structure directing agents and extensively characterized for their textural, structural, and catalytic properties. Introduction of Fe(3+) ions in the framework of nanosheet zeolites was slightly less effective than in bulk ZSM-5 zeolite. Steaming was necessary to activate all catalysts for N2O decomposition and benzene oxidation. The higher the Fe content, the higher the degree of Fe aggregation was after catalyst activation...
April 7, 2017: ACS Catalysis
Deepak Tiwari, Chitrakshi Goel, Haripada Bhunia, Pramod K Bajpai
In this work, we report carbon adsorbents obtained from high nitrogen content melamine-formaldehyde resin as starting material and mesoporous zeolite MCM-41 as template through nanocasting technique. To synthesize different carbon structure adsorbents with improved textural and surface properties, the material undergo carbonization followed by physical activation under CO2 atmosphere at different temperatures. Characterizations of the adsorbents using SEM, TEM, XPS, nitrogen sorption, CHN, TKN, and TPD have been carried out...
April 12, 2017: Journal of Environmental Management
Xiangke Kong, Guoxin Huang, Zhantao Han, Youming Xu, Ming Zhu, Zhaoji Zhang
A new composite adsorbent, zeolite-supported microscale zero-valent iron (Z-mZVI) was evaluated as a potential adsorbent for the removal of Cd(2+) and Pb(2+) from aqueous solution using batch and column experiments. Adsorption isotherms were well fitted by Langmuir model, and the maximum adsorption capacity was 63.14 mg/g for Cd(2+) and 154.61 mg/g for Pb(2+), respectively. Both adsorption processes followed the pseudo-second-order model which indicated that the rate-limiting step for different initial concentration was dominated by chemical adsorption process...
April 13, 2017: Environmental Science and Pollution Research International
E Broclawik, K Góra-Marek, M Radoń, T Bučko, A Stępniewski
This work is focused on the donor properties of cobalt-exchanged cationic sites in zeolites. It is based on cluster and periodic density functional theory modeling for relevant {[Co(II)(NH3)n]-NO} adducts, where Co(II) means a cobalt cation embedded either in a periodic model of chabasite (CHA) zeolite or in model clusters. NO stretching frequencies were derived from MD trajectories and compared to harmonic values from cluster calculations. By relating calculated NO frequencies to experimental FTIR spectra, it was shown that the forms of {Co(II)-NO} adducts comprising three or four ammonia co-ligands dominate the spectrum taken in ammonia-saturation conditions while forms with two NH3 ligands prevail under intermediate ammonia saturation...
May 2017: Journal of Molecular Modeling
Tongzhou Liu, Hong Wang, Zhen Zhang, Da Zhao
Contaminants released from river sediments are catching more attentions for river environmental management, especially when external sources of river pollution have been well controlled. To reduce the contaminant release from sediments, in-situ capping is often applied because of its effective reduction of contaminant flux and minimal disturbance to the surroundings. As an innovative sediment capping material, iron-oxide coated zeolite (IOCZ) was synthesized, characterized, and evaluated in this study. Its performance for the NH4(+)-N, PO4(3-)-P, and S(2-)-S fixation in aqueous solutions was evaluated using batch and fixed-bed column experiments...
April 6, 2017: Chemosphere
Yanhong Quan, Shiying Li, Sen Wang, Zhikai Li, Mei Dong, Zhangfeng Qin, Gang Chen, Zhihong Wei, Weibin Fan, Jianguo Wang
Chainlike zeolites are advantageous to various applications as a catalyst or an adsorbent with specific selectivity; however, it is often very difficult to get desired morphology due to the complexity of zeolite synthesis process. In this work, appropriate parameters for the synthesis of perfect chainlike ZSM-5 zeolites were well determined, which illustrates that the chain length can be controlled by the composition of synthesis mixture, the amount of residual alcohol in the synthesis system, and the crystallization time...
April 18, 2017: ACS Applied Materials & Interfaces
Peng Ji, Kun Lu, Xinqing Lu, Hao Xu, Peng Wu
Ti-SSZ-70 and Ti-ECNU-6, with identical intralayer structures but distinct interlayer connections, were prepared from similar synthetic gels free of alkali metal ions and boric acid. Ti-SSZ-70, composed of vertically misaligned MWW layers, was transferred to Ti-ECNU-6, structurally analogous to the Ti-MWW zeolite with a well-aligned layer stacking, upon the addition of an appropriate amount of hexamethyleneimine to the gel. These two titanosilicate catalysts exhibited outstanding catalytic activities in the liquid-phase alkene epoxidation...
April 12, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Jingjing Yang, Yue-Biao Zhang, Qi Liu, Christopher A Trickett, Enrique Gutierrez-Puebla, M Ángeles Monge, Hengjiang Cong, Abdulrahman Aldossary, Hexiang Deng, Omar M Yaghi
We report three design principles for obtaining extra-large pore openings and cages in the metal-organic analogues of inorganic zeolites, zeolitic imidazolate frameworks (ZIFs). Accordingly, we prepared a series of fifteen ZIFs, members of which have the largest pore opening (22.5 Å) and the largest cage size (45.8 Å) known for all porous tetrahedral structures. The key parameter allowing us to access these exceptional ZIFs is what we define as the steric index (δ), which is related to the size and shape of the imidazolate linkers employed in the synthesis...
April 11, 2017: Journal of the American Chemical Society
Cheng Zhang, Xuerui Wang, Miao Hou, Xiaoyang Li, Xiaoling Wu, Jun Ge
The protection effect of metal-organic framework (MOF) provides high stability for immobilized enzyme. The small cavities of MOFs, however, usually result in decreased apparent substrate affinity and enzymatic activity of immobilized enzyme, compared to native enzyme. We synthesized zeolitic imidazolate framework-8 (ZIF-8) with a combination of mesoporous and microporous channels for cytochrome c (Cyt c) immobilization. Compared with native Cyt c, the immobilized Cyt c displayed increased apparent substrate affinity (Michaelis constant Km reduced by ∼50%), ∼128% increased enzymatic activity, and 1...
April 13, 2017: ACS Applied Materials & Interfaces
Gion Calzaferri
Analysis of multiple equilibria where the binding enthalpy of the species is the same for all sites and independent of those that are already bonded delivers insight on the evolution of the entropy as the reactions proceed and explains why the equilibrium constants always decrease with increasing number of occupied sites. The validity of the results is independent of the nature of bonding. Consequences are explained by discussing dicarboxylic acids, cation exchange of zeolite A, and the insertion of guests into the one-dimensional channels of zeolite L, by cation exchange for cationic guests and from the gas phase for neutral molecules...
April 19, 2017: Physical Chemistry Chemical Physics: PCCP
Jun Chen, Guang-Guo Ying, You-Sheng Liu, Xiao-Dong Wei, Shuang-Shuang Liu, Liang-Ying He, Yong-Qiang Yang, Fan-Rong Chen
This study aims to investigate nitrogen removal and its relationship with the nitrogen-cycle genes and microorganisms in the horizontal subsurface flow constructed wetlands (CWs) with different design parameters. Twelve mesocosm-scale CWs with four substrates and three hydraulic loading rates were set up in the outdoor. The result showed the CWs with zeolite as substrate and HLR of 20 cm/d were selected as the best choice for the TN and NH3-N removal. It was found that the single-stage mesocosm-scale CWs were incapable to achieve high removals of TN and NH3-N due to inefficient nitrification process in the systems...
April 10, 2017: Journal of Environmental Science and Health. Part A, Toxic/hazardous Substances & Environmental Engineering
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