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Pfano Mathews Nekhunguni, Nikita Tawanda Tavengwa, Hlanganani Tutu
Zeolites are commonly used as adsorbents for metal removal in most applications e.g. in wastewater. However, the ubiquity of iron in such systems may, in the long-term, distort the true interactions and mechanisms of contaminant removal as a result of modification of the zeolite surface. In this study, this potential phenomenon was assessed for the removal of uranium(VI) from aqueous solution by hydrous ferric oxide-modified zeolite (HFOMZ). This was prepared by precipitating iron hydroxide (the common precipitate of iron in aqueous systems) onto zeolite...
September 19, 2017: Journal of Environmental Management
James Wainaina Maina, Jurg Schutz, Luke Grundy, Elise Des Ligneris, Zhifeng Yi, Lingxue Kong, Cristina Pozo-Gonzalo, Mihail Ionescu, Ludovic F Dumée
Photocatalytic conversion of carbon dioxide (CO2) to useful products has potential to address the adverse environmental impact of global warming. However, most photocatalysts used to date exhibit limited catalytic performance, due to poor CO2 adsorption capacity, inability to efficiently generate photoexcited electrons, and/or poor transfer of the photo-generated electrons to CO2 molecules adsorbed on the catalyst surface. The integration of inorganic semiconductor nanoparticles across metal organic framework (MOF) materials has potential to yield new hybrid materials, combining high CO2 adsorption capacity of MOF and the ability of the semiconductor nanoparticles to generate photoexcited electrons...
September 22, 2017: ACS Applied Materials & Interfaces
Jérôme Roeser, Dragica Prill, Michael J Bojdys, Pierre Fayon, Abbie Trewin, Andrew N Fitch, Martin U Schmidt, Arne Thomas
Crystalline frameworks composed of hexacoordinate silicon species have thus far only been observed in a few high pressure silicate phases. By implementing reversible Si-O chemistry for the crystallization of covalent organic frameworks, we demonstrate the simple one-pot synthesis of silicate organic frameworks based on octahedral dianionic SiO6 building units. Clear evidence of the hexacoordinate environment around the silicon atoms is given by (29)Si nuclear magnetic resonance analysis. Characterization by high-resolution powder X-ray diffraction, density functional theory calculation and analysis of the pair-distribution function showed that those anionic frameworks-M2[Si(C16H10O4)1...
October 2017: Nature Chemistry
Samuel A Morris, Giulia P M Bignami, Yuyang Tian, Marta Navarro, Daniel S Firth, Jiří Čejka, Paul S Wheatley, Daniel M Dawson, Wojciech A Slawinski, David S Wragg, Russell E Morris, Sharon E Ashbrook
The assembly-disassembly-organization-reassembly (ADOR) mechanism is a recent method for preparing inorganic framework materials and, in particular, zeolites. This flexible approach has enabled the synthesis of isoreticular families of zeolites with unprecedented continuous control over porosity, and the design and preparation of materials that would have been difficult-or even impossible-to obtain using traditional hydrothermal techniques. Applying the ADOR process to a parent zeolite with the UTL framework topology, for example, has led to six previously unknown zeolites (named IPC-n, where n = 2, 4, 6, 7, 9 and 10)...
October 2017: Nature Chemistry
Peng Gao, Shenggang Li, Xianni Bu, Shanshan Dang, Ziyu Liu, Hui Wang, Liangshu Zhong, Minghuang Qiu, Chengguang Yang, Jun Cai, Wei Wei, Yuhan Sun
Although considerable progress has been made in carbon dioxide (CO2) hydrogenation to various C1 chemicals, it is still a great challenge to synthesize value-added products with two or more carbons, such as gasoline, directly from CO2 because of the extreme inertness of CO2 and a high C-C coupling barrier. Here we present a bifunctional catalyst composed of reducible indium oxides (In2O3) and zeolites that yields a high selectivity to gasoline-range hydrocarbons (78.6%) with a very low methane selectivity (1%)...
October 2017: Nature Chemistry
Mukesh Sharma, Biraj Das, Mitu Sharma, Biplab K Deka, Young-Bin Park, Suresh K Bhargava, Kusum K Bania
Solid-state grinding of palladium and copper salts allowed the growth of palladium/copper oxide interface at the zeolite-Y surface. The hybrid nanostructured material was used as reusable heterogeneous catalyst for selective oxidation of various benzyl alcohols. The large surface area provided by the zeolite-Y matrix highly influenced the catalytic activity as well as the recyclability of the synthesized catalyst. Impregnation of PdO-CuO nanoparticles on zeolite crystallite leads to the generation of mesoporous channel that probably prevented the leaching of the metal-oxide nanoparticles and endorsed high mass transfer...
September 21, 2017: ACS Applied Materials & Interfaces
Wenda Hu, Yan Wan, Lili Zhu, Xiaojie Cheng, Shaolong Wan, Jingdong Lin, Yong Wang
Herein we report a strategy to simultaneously produce two important chemicals namely Methallyl alcohol (Mol) and diethyl acetal (Dal) from methacrolein (Mal) in ethanol solvent at low temperature with the use of Beta zeolites modified by tin (Sn-β catalysts). All Sn-β catalysts were prepared by the solid-state ion-exchange (SSIE) method, wherein the calcination step was conducted in different gas atmospheres. The one pre-calcined in Ar (Sn-β-Ar) diminishes the number of extra-framework Sn species and instead enables more Sn species exchanged into the framework as isolated tetrahedral Sn (IV), thus enhancing the catalytic activity of Meerwein-Ponndorf-Verley (MPV) reaction...
September 19, 2017: ChemSusChem
Dong Jiang, Zeyu Zhao, Shenglong Mu, Vincent Phaneuf, Jianhua Tong
Mayenite (12CaO·7Al2O3, C12A7) electride with an anti-zeolite nanoporous structure has attracted intense attention due to its versatile promising application potentials. However, the synthesis difficulty because of extremely harsh conditions (e.g., reduction in sealed calcium or titanium vapor) significantly obstructs its realistic applications. In this work, we employed a simple, efficient, and cost-effective route for synthesizing mayenite electrides (C12A7:e(-)) in both powder and dense ceramic. C12A7:e(-) powders with efficient electron doping (3...
September 19, 2017: Inorganic Chemistry
Zhixiong Luo, Somboon Chaemchuen, Kui Zhou, Francis Verpoort
The catalytic activity of ZIF-8 in the ring-opening polymerization of L-lactide without solvents or co-catalysts is presented for the first time. Two different synthetic strategies have been applied for synthesizing ZIF-8, either under solvothermal condition or by spray-drying procedure. Their catalytic activities are found to be correlating with the presence of open active sites in ZIF-8 structure. The structural defects which afford active acid and basic sites are supposed to cooperatively catalyze the reaction...
September 18, 2017: ChemSusChem
Marcel Handke, Takuji Adachi, Chunhua Hu, Michael D Ward
The sequestration of luminophores within supramolecular polyhedral compartments of a crystalline zeolite-like hydrogen-bonded framework illustrates a unique approach to limiting the self-quenching ordinarily exhibited at the high concentrations achievable in this framework. A range of differently sized luminescent guests, namely coumarin 1, coumarin 4, fluorescein, [Ru(bpy)3 ]Cl2 , and rhodamine B, can be encapsulated in amounts of up to one molecule per cage, equivalent to a concentration of 0.175 m, which is significantly higher than the concentration at which aggregation-induced quenching occurs in other media...
September 18, 2017: Angewandte Chemie
Hao Chen, Min Qiang Wang, Yanan Yu, Heng Liu, Shi-Yu Lu, Shu-Juan Bao, Maowen Xu
Metal-origanic frameworks (MOF)-derived hollow cobalt sulfides have attracted extensive attention due to their porous shell that provides rich redox reactions for energy storage. However, their ultra-dispersed structure and large size of MOFs precursors result in relatively low conductivity, stability, and low tap density .Therefore, the construction of an array of continuous hollow cages and tailor the inner cavity of MOF-derived materials is very effective for enhancing the electrochemical performance. Herein, we in situ assembled small Co-based zeolitic imidazolate framework (ZIF-67) on the both sides of negatively charged MnO2 nanosheets to fabricate a hierarchical sandwich-type composite with hollow cobalt sulfide nanocages/graphene-like MnO2...
September 18, 2017: ACS Applied Materials & Interfaces
Zehui Li, Lan Yang, Hongbin Cao, Yu Chang, Kexin Tang, Zhiqin Cao, Junjun Chang, Youpeng Cao, Wenbo Wang, Meng Gao, Chenming Liu, Dagang Liu, He Zhao, Yi Zhang, Mingjie Li
In order to promote sustainable development, green and renewable clean energy technologies continue to be developed to meet the growing demand for energy, such as supercapacitor, fuel cells and lithium-ion battery. It is urgent to develop appropriate nanomaterials for these energy technologies to reduce the volume of the device, improve the efficiency of energy conversion and enlarge the energy storage capacity. Here, chitosan/cellulose carbon cryogel (CCS/CCL) were designed and synthesized. Through the introduction of zeolite imidazole frameworks (ZIFs) into the chitosan/cellulose cryogels, the obtained materials showed a microstructure of ZIF-7 (a kind of ZIFs) coated chitosan/cellulose fibers (CS/CL)...
November 1, 2017: Carbohydrate Polymers
Camila Gomes Flores, Helena Schneider, Nilson Romeu Marcilio, Lizete Ferret, João Carlos Pinto Oliveira
Brazilian coal has an ash content ranging from 30 to 50% by weight. Consequently, its use in coal-fired thermoelectric for power production generates a lot of waste. The construction sector is the largest consumer of coal ash, but it cannot absorb the entire amount generated. Thus, other applications for coal ash should be studied in aim to optimize the use of this industrial waste. This research had as focus to synthesize potassic zeolite from of the coal ash into on potassium fertilizer for the grown wheat plant...
September 13, 2017: Waste Management
Mukesh Kumar Awasthi, Ammaiyappan Selvam, Ka Man Lai, Jonathan W C Wong
Effect of single-function (oil degrading) and multi-functional bacterial consortium with zeolite as additive for post-consumption food waste (PCFW) composting was investigated through assessing the oil content reduction in a computer controlled 20-L composter. Three treatments of PCFWs combined with 10% zeolite were developed: Treatment-2 and Treatment-3 were inoculated with multi-functional (BC-1) and oil degrading bacterial consortium (BC-2), respectively, while T-1 was without bacterial inoculation and served as control...
September 5, 2017: Bioresource Technology
Dmitri G Fedorov, Kazuo Kitaura
A many-body expansion of the Fock matrix in the fragment molecular orbital method is derived up to three-body terms for restricted Hartree-Fock and density functional theory in the atomic orbital basis and compared to the expansion in the basis of fragment molecular orbitals (MOs). The physical nature of many-body corrections is revealed in terms of charge transfer terms. An improvement of the fragment MO expansion is proposed by adding exchange to the embedding. The accuracy of all developed methods is demonstrated in comparison to unfragmented results for polyalanines, a water cluster, Trp-cage (PDB: 1L2Y) and crambin (PDB: 1CRN) proteins, a zeolite cluster, a Si nano-wire, and a boron nitride ribbon...
September 14, 2017: Journal of Chemical Physics
Yun Tian, Xiaofei Xu, Jianzhong Wu
We report an efficient computational procedure for rapid and accurate prediction of the self-diffusivity of gas molecules in nanoporous materials by implementing the transitional-state theory for inter-cage hopping at infinite dilution with the string method in conjunction with the excess-entropy scaling for predicting gas diffusion at finite loadings. The theoretical procedure has been calibrated with molecular dynamics simulations for the diffusion coefficients of methane and hydrogen gases in representative nanoporous materials including metal organic frameworks and zeolites...
September 15, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Edoardo Garrone, Montserrat R Delgado, Barbara Bonelli, Carlos O Arean
The current state of the art in the application of variable-temperature IR (VTIR) spectroscopy to the study of (i) adsorption sites in zeolites, including dual cation sites; (ii) the structure of adsorption complexes and (iii) gas-solid interaction energy is reviewed. The main focus is placed on the potential use of zeolites for gas separation, purification and transport, but possible extension to the field of heterogeneous catalysis is also envisaged. A critical comparison with classical IR spectroscopy and adsorption calorimetry shows that the main merits of VTIR spectroscopy are (i) its ability to provide simultaneously the spectroscopic signature of the adsorption complex and the standard enthalpy change involved in the adsorption process; and (ii) the enhanced potential of VTIR to be site specific in favorable cases...
September 15, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Yong Chen, Xinping Wang, Lejian Zhang
It was found that bands at 739, 963 and 1107 cm-1 in resonant Raman spectra are characteristics of framework penta-coordinated NbV-OH species, and that band at 1336 cm-1 in UV Raman spectra excited by 320 nm is a sensitive detector to identify extraframework niobium species. The change of framework penta-coordinated NbV-OH species into Nb+ and NbO- species due to dehydration was definitively confirmed based on UV resonance Raman and UV/Vis results.
September 14, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Luis Fernando Mercier Franco, Ioannis George Economou, Marcelo Castier
We extend the SAFT-VR Mie equation of state to calculate adsorption isotherms by considering explicitly the residual energy due to the confinement effect. Assuming a square-well potential for the fluid-solid interactions, the structure imposed by the fluid-solid interface is calculated using two different approaches: an empirical expression proposed by Travalloni et al. (Chem. Eng. Sci., 65, 3088-3099, 2010), and a new theoretical expression derived by applying the mean value theorem. Adopting the SAFT-VR Mie (Lafitte et al...
September 14, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Hyunsoo Lee, Kyoungsoo Kim, Seoung-Hun Kang, Yonghyun Kwon, Jong Hun Kim, Young-Kyun Kwon, Ryong Ryoo, Jeong Young Park
We report the remarkably high electrical conductance of microporous 3D graphene-like carbons that were formed using lanthanum (La)-catalyzed synthesis in a Y zeolite (LaY) template investigated using conductive atomic force microscopy (C-AFM) and theoretical calculations. To uncover the relation between local electrical conductance and the microporous structures, we tuned the crystallographic ordering of LaY-templated carbon systems by changing the heating temperature. The structure of the LaY-templated carbon prepared at the higher temperature has graphene-like sp (2) hybridized bonds, which was confirmed using high-resolution transmission electron microscopy and X-ray diffraction measurements...
September 13, 2017: Scientific Reports
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