The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Pingyun Feng - One of the best experts on this subject based on the ideXlab platform.
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Pore Space partition enabled exceptional ethane uptake and ethane selective ethane ethylene separation
Journal of the American Chemical Society, 2020Co-Authors: Huajun Yang, Yanxiang Wang, R Krishna, Yong Wang, Anh N Hong, Candy Dang, Henry E Castillo, Xianhui Bu, Pingyun FengAbstract:An ideal material for C2H6/C2H4 separation would simultaneously have the highest C2H6 uptake capacity and the highest C2H6/C2H4 selectivity. But such material is elusive. A benchmark material for ethane-selective C2H6/C2H4 separation is peroxo-functionalized MOF-74-Fe that exhibits the best known separation performance due to its high C2H6/C2H4 selectivity (4.4), although its C2H6 uptake capacity is moderate (74.3 cm3/g). Here, we report a family of Pore-Space-partitioned crystalline porous materials (CPMs) with exceptional C2H6 uptake capacity and C2H6/C2H4 separation potential (i.e., C2H4 recovered from the mixture) despite their moderate C2H6/C2H4 selectivity (up to 1.75). The ethane uptake capacity as high as 166.8 cm3/g at 1 atm and 298 K, more than twice that of peroxo-MOF-74-Fe, has been achieved even though the isosteric heat of adsorption (21.9-30.4 kJ/mol) for these CPMs is as low as about one-third of that for peroxo-MOF-74-Fe (66.8 kJ/mol). While the overall C2H6/C2H4 separation potentials have not yet surpassed peroxo-MOF-74-Fe, these robust CPMs exhibit outstanding properties including high thermal stability (up to 450 °C) and aqueous stability, low regeneration energy, and a high degree of chemical and geometrical tunability within the same isoreticular framework.
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a tale of two trimers from two different worlds a cof inspired synthetic strategy for Pore Space partitioning of mofs
Angewandte Chemie, 2019Co-Authors: Yanxiang Wang, Xiang Zhao, Huajun Yang, Yong Wang, Xiaoxia Jia, Pingyun FengAbstract:The introduction of a symmetry- and size-matching Pore-partitioning agent in the form of either a molecular ligand, such as 2,4,6-tri(4-pyridinyl)-1,3,5-triazine (tpt), or a metal-complex cluster, into the hexagonal channels of MIL-88/MOF-235-type (the acs net) to create pacs-type (partitioned acs) crystalline porous materials is an effective strategy to develop high-performance gas adsorbents. We have developed an integrated COF-MOF coassembly strategy as a new method for Pore-Space partitioning through the coassembly of [(M3 (OH)1-x (O)x (COO)6 ] MOF-type and [B3 O3 (py)3 ] COF-type trimers. With this strategy, the coordination-driven assembly of the acs framework occurred concurrently and synergistically with the COF-1-type condensation of pyridine-4-boronic acid into a C3 -symmetric trimeric boroxine molecule. The resulting boroxine-based pacs materials exhibited dramatically enhanced gas-sorption properties as compared to nonpartitioned acs-type materials and are among the most efficient NH3 -sorption materials.
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Pore Space partition in metal organic frameworks
Accounts of Chemical Research, 2017Co-Authors: Quanguo Zhai, Xiang Zhao, Pingyun FengAbstract:ConspectusMetal–organic framework (MOF) materials have emerged as one of the favorite crystalline porous materials (CPM) because of their compositional and geometric tunability and many possible applications. In efforts to develop better MOFs for gas storage and separation, a number of strategies including creation of open metal sites and implantation of Lewis base sites have been used to tune host–guest interactions. In addition to these chemical factors, the geometric features such as Pore size and shape, surface area, and Pore volume also play important roles in sorption energetics and uptake capacity. For efficient capture of small gas molecules such as carbon dioxide under ambient conditions, large surface area or high Pore volume are often not needed. Instead, maximizing host–guest interactions or the density of binding sites by encaging gas molecules in snug pockets of Pore Space can be a fruitful approach. To put this concept into practice, the Pore Space partition (PSP) concept has been proposed ...
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multivariable modular design of Pore Space partition
Journal of the American Chemical Society, 2016Co-Authors: Xiang Zhao, Quanguo Zhai, Edward T Nguyen, Chengyu Mao, Pingyun FengAbstract:Pore Space partition, especially the one using C3-symmetric 2,4,6-tri(4-pyridyl)-1,3,5-triazine as Pore-partition agent in MIL-88 type (the acs net), has been shown to dramatically enhance CO2 uptake to near-record values. The continued advance in property engineering via Pore Space partition would depend on intelligent design of both framework components and Pore-partition agent. Here, we report a new advance in the design of Pore-partition agent by demonstrating a symmetry-guided pathway to develop a large variety of di- and trinuclear 1,2,4-triazolate-based clusters for use as Pore-partition agent. The use of metal–organic clusters (instead of organic ligands) as Pore-partition agent gives rise to many new Pore-partitioned materials with huge compositional variety. The full assembly involves the simultaneous formation of two separate coordination architectures (i.e., the 3-D acs framework and 0-D triazolate clusters) and the eventual welding between the acs framework and triazolate clusters. The wide r...
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Pore Space partition by symmetry matching regulated ligand insertion and dramatic tuning on carbon dioxide uptake
Journal of the American Chemical Society, 2015Co-Authors: Xiang Zhao, Quanguo Zhai, Huy Tran, Pingyun FengAbstract:Metal–organic frameworks (MOFs) with the highest CO2 uptake capacity are usually those equipped with open metal sites. Here we seek alternative strategies and mechanisms for developing high-performance CO2 adsorbents. We demonstrate that through a ligand insertion Pore Space partition strategy, we can create crystalline porous materials (CPMs) with superior CO2 uptake capacity. Specifically, a new material, CPM-33b-Ni without any open metal sites, exhibits the CO2 uptake capacity comparable to MOF-74 with the same metal (Ni) at 298 K and 1 bar.
Josef Kaufmann - One of the best experts on this subject based on the ideXlab platform.
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Pore Space analysis of cement based materials by combined nitrogen sorption wood s metal impregnation and multi cycle mercury intrusion
Cement & Concrete Composites, 2010Co-Authors: Josef KaufmannAbstract:Abstract The analysis of Pore Space is crucial for a profound understanding of transport and mechanical properties of porous materials. Cement-based materials have a broad Pore size distribution ranging from micro- to macro-Pores. The analysis of this kind of Pore Space therefore becomes difficult. Because the resolution of image based methods is limited, indirect analysis methods like Nitrogen sorption or mercury intrusion porosimetry (MIP) are often applied. The standard MIP results in an underestimation of large Pores because of its intrinsic limitation due to ink-bottle type Pores (i.e., Pores that are connected to the surface by smaller neck entrances only). The adsorption of Nitrogen seems to be less influenced by such connectivity effects, but the analysis of Pores larger than about 100 nm is not possible. To overcome these limitations, in this study Pores were selectively filled with Wood’s metal. The liquid metal (at elevated temperature) is intruded into the samples by applying different pressure regimes and then re-solidified in place. The partial impregnation with this metal allowed the analysis of non-ink-bottle type Pore Space in a subsequent Nitrogen sorption experiment and its comparison with an empty Pore system. Furthermore, Mercury intrusion experiments with an additional pressurization–depressurization cycles (multi-cycle-MIP) were performed. The Pore size distributions and Pore volumes as calculated from Nitrogen sorption data are then compared with MIP and multi-cycle MIP data.
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characterization of Pore Space of cement based materials by combined mercury and wood s metal intrusion
Journal of the American Ceramic Society, 2009Co-Authors: Josef KaufmannAbstract:Analysis of the Pore Space is crucial for a profound understanding of the transport and mechanical properties of porous materials. Mercury intrusion porosimetry (MIP) is an easy and widely applied method to determine the Pore size distribution of mesoporous materials, but a principal problem makes data interpretation difficult. Large ink-bottle Pores may be accessed by the intruding mercury through smaller, so-called neck Pores only. This leads to significant under estimaion of Pore sizes and to hysteresis effects between intrusion and extrusion in materials with a broad Pore size distribution such as cement-based materials. More accurate Pore Space information is obtained when ink-bottle Pores in the measurement are excluded from analysis. This may be achieved by repeated intrusion cycles or by impregnating the ink-bottle Pore Space with Wood's metal. The combination of Wood's metal impregnation (WMI) and mercury intrusion in mortars and cement pastes as presented allows a characterization of the Pore Space independent of accessibility considerations. Different special Pore types are defined, analyzed, and quantified. In a cement paste, 50% of all Pores are found to be ink-bottle type, of which 60% are accessible through neck entrances larger than 20 nm in diameter. A further 30% of all Pores are nonink-bottle type but are connected to the surface through such ink-bottle Pores only. Furthermore, hysteresis and contact angle alternation effects between intrusion and extrusion were studied. A contact angle shift of 26° between intrusion and extrusion is proposed.
Keith Smith - One of the best experts on this subject based on the ideXlab platform.
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The effects of temperature, water-filled Pore Space and land use on N2O emissions from an imperfectly drained gleysol
European Journal of Soil Science, 2001Co-Authors: K. E. Dobbie, Keith SmithAbstract:Summary To investigate the effect of soil physical conditions and land use on emissions of nitrous oxide (N2O) to the atmosphere, soil cores of an imperfectly drained gleysol were taken from adjacent fields under perennial ryegrass and winter wheat. The cores were fertilized with ammonium nitrate and incubated at three different temperatures and water-filled Pore Space (WFPS) values, and N2O emissions were measured by gas chromatography. Emissions showed a very large response to temperature. Apparent values of Q10 (emission rate at (T + 10)°C/emission rate at T°C) for the arable soil were about 50 for the 5–12°C interval and 8.9 for 12–18°C; the corresponding Q10s for the grassland soil were 3.7 and 2.3. Emissions from the grassland soil were always greater than those from the arable soil, although the ratio narrowed with increasing temperature. Changes in soil WFPS also had a profound effect on emissions. Those from the arable soil increased about 30-fold as the WFPS increased from 60 to 80%, while that from the grassland soil increased 12-fold. This latter response was similar to earlier field measurements. The N2O emissions were considered to be produced primarily by denitrification. We concluded that the impacts of temperature and WFPS on emissions could both be explained on the basis of existing models relating increasing respiration or decreased oxygen diffusivity, or both, to the development of anaerobic zones within the soil.
Alan J Franzluebbers - One of the best experts on this subject based on the ideXlab platform.
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microbial activity in response to water filled Pore Space of variably eroded southern piedmont soils
Applied Soil Ecology, 1999Co-Authors: Alan J FranzluebbersAbstract:Abstract Potential C and N mineralization and soil microbial biomass C (SMBC) are soil biological properties important in understanding nutrient and organic matter dynamics. Knowledge of soil water content at a matric potential near field capacity is needed to determine these biological properties. The objective of this study was to examine whether adjustment of soil water content to a common level of water-filled Pore Space (WFPS) may be an acceptable alternative that would require little prior analysis in comparison with adjustment based on matric potential. Potential C and N mineralization and SMBC were determined from 15 variably eroded soils of the Madison–Cecil–Pacolet association (clayey, kaolinitic, thermic Typic Kanhapludults) in response to WFPS. The levels of WFPS to achieve maximum activity and biomass under naturally settled conditions were unaffected by clay content and occurred at 0.42±0.03 m 3 m −3 for net N mineralization during 24 days of incubation, 0.51±0.22 m 3 m −3 for specific respiratory activity of SMBC, 0.60±0.07 m 3 m −3 for cumulative C mineralization during 24 d of incubation, and 0.76±0.27 m 3 m −3 for SMBC. Selecting a common WFPS level of 0.5 m 3 m −3 resulted in 96±2%, 97±5%, 97±4%, and 88±10% of the maximum for these four properties, respectively, and was a reasonable compromise when attempting to estimate these properties during simultaneous incubations. Adjusting soil water content based on WFPS was simpler and nearly as reliable as based on matric potential, in which soil water content at −33 kPa varied from 0.16 to 0.30 g g −1 .
Graham W Horgan - One of the best experts on this subject based on the ideXlab platform.
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dynamics of upward and downward n2o and co2 fluxes in ploughed or no tilled soils in relation to water filled Pore Space compaction and crop presence
Soil & Tillage Research, 2008Co-Authors: B C Ball, I Crichton, Graham W HorganAbstract:Sharp peaks in nitrous oxide (N2O) fluxes under no-tillage in wet conditions appear to be related to near surface soil and crop cover conditions. Here we explored some of the factors influencing tillage effects on short-term variations in gas flux so that we could learn about the mechanisms involved. Field investigations revealed that a cumulative emission of 13 kg N2O–N ha−1 over a 12-week period was possible under no-tillage for spring barley. We investigated how reducing crop cover and changing the structural arrangement of the water-filled Pore Space (WFPS) by short-term laboratory compaction influenced N2O and carbon dioxide (CO2) fluxes in upward and downward directions in core samples from tilled and untilled soil. Increasing the downward flux of N2O within a soil profile by changing soil or moisture conditions may increase the likelihood of its further reduction to N2 or dissolution. We took undisturbed cores from 3 to 8 cm depth, equilibrated them to −1 or −6 kPa matric potential, incubated them and measured N2O and CO2 fluxes from the upper and lower surfaces in a purpose-designed apparatus before and after compaction in an uniaxial tester. We also measured WFPS, air permeability, bulk density and air-filled porosity before and after compaction. Spring barley was tested in 1999 and winter barley in 2000. Fluxes of N2O were from 1.5 to 35 times higher from no-tilled than ploughed even where the soil was of similar bulk density. Reduction of the crop cover increased CO2 flux and could reduce N2O flux. The effects of structural changes induced by laboratory compaction on the fluxes of N2O and CO2 were not influenced greatly by the tillage and crop cover treatments. Fluxes from the upper surfaces of cores (corresponding to 3 cm soil depth, upwards direction) could be up to ∼100 times greater (N2O) or ∼8 times (CO2) than from the lower surfaces (8 cm depth, downwards direction). These differences between surfaces were greatest when N2O fluxes were very high in no-tilled soil (4.2 mg N2O–N m−2 h−1) as occurred when WFPS exceeded 80% or became blocked with water, an effect that was increased by our compaction treatment. In general N2O fluxes increased with WFPS. The production and emission of N2O were strongly influenced by the soil physical environment, the magnitude of the water-filled Pore Space and continuity of the air-filled Pore Space in particular, produced in no-till versus plough cultivation.