232 research outputs found
SYSTEMATIC POSTSYNTHETIC MODIFICATION OF NANOPOROUS ORGANIC FRAMEWORKS AND THEIR PERFORMANCE EVALUATION FOR SELECTIVE CO2 CAPTURE
No full textPorous organic polymers (POPs) with high physicochemical stability have attracted significant attention from the scientific community as promising platforms for small gas separation adsorbents. Although POPs have amorphous morphology in general, with the help of organic chemistry toolbox, ultrahigh surface area materials can be synthesized. In particular, nitrogen-rich POPs have been studied intensively due to their enhanced framework-CO2 interactions. Postsynthetic modification (PSM) of POPs has been instrumental for incorporating different functional groups into the pores of POPs which would increase the CO2 capture properties. We have shown that functionalizing the surface of POPs with nitro and amine groups increases the CO/N2 and CO2/CH4 selectivity significantly due to selective polarization of CO2 molecule. In addition, controlled postsynthetic nitration of NPOF-1, a nanoporous organic framework constructed by nickel(0)-catalyzed Yamamoto coupling of 1,3,5-tris(4-bromophenyl)benzene, has been performed and is proven to be a promising route to introduce nitro groups and to convert mesopores to micropores without compromising surface area. Reduction of the nitro groups yields aniline-like amine-functionalized NPOF-1-NH2. Adequate basicity of the amine functionalities leads to modest isosteric heats of adsorption for CO2, which allow for high regenerability. The unique combination of high surface area, microporous structure, and amine-functionalized pore walls enables NPOF-1-NH2 to have remarkable CO2 working capacity values for removal from landfill gas and flue gas. Benzimidazole-linked polymers have also been shown to have promising CO2 capture properties. Here, an amine functionalized benzimidazole-linked polymer (BILP-6-NH2) was synthesized via a combination of pre- and postsynthetic modification techniques in two steps. Experimental studies confirm enhanced CO2 uptake in BILP-6-NH2 compared to BILP-6, and DFT calculations were used to understand the interaction modes of CO2 with BILP-6-NH2. Using BILP-6-NH2, higher CO2 uptake and CO2/CH4 selectivity was achieved compared to BILP-6 showing that this material has a very promising working capacity and sorbent selection parameter for landfill gas separation under VSA settings. Additionally, the sorbent evaluation criteria of different classes of organic polymers have been compared in order to reveal structure-property relationships in those materials as solid CO2 adsorbents
The Evolution of Grain Policy Beyond Europe: Ottoman Grain Administration in the Late Eighteenth Century
No full textDuring the second half of the eighteenth century, the Ottoman policy-makers adopted a more liberal attitude towards price formation in the Ottoman grain markets. This was accompanied by the fiscal and administrative centralization of the grain trade. These seemingly contradictory policy changes could, in part, be explained in the context of conjectural changes in grain demand and supply, which rendered pre-emptive privileges and price controls less effective. The policy change, however, was not only a practical response to the strains on the pre-existing supply network but also reflected a new concern with the state of agricultural production along with the emergence of emulation as a development strategy.Ottoman economic institutions, grain markets, liberalization
Toward Base Heterogenization: A Zirconium Metal–Organic Framework/Dendrimer or Polymer Mixture for Rapid Hydrolysis of a Nerve-Agent Simulant
No full textThe base heterogenization
is crucial for the practical applications
of metal–organic frameworks (MOFs) as catalytic filters, such
as masks or protective suits, for the deconstruction of chemical warfare
agents (CWAs). Here, we performed the hydrolysis of a phosphate-based
nerve agent simulant in the presence of different amine-based bases
(i.e., a small organic molecule, dendrimers, and linear and branched
polymers) using a Zr-MOF, NU-901, with 4,8-connected scu topology. Remarkably, the catalytic performances of NU-901 using
the less-volatile branched polymers and dendrimers are comparable
to the volatile N-ethylmorpholine solution
Computational investigation of the velocity and temperature fields in corrugated heat exchanger channels using RANS based turbulence models with experimental validation
No full textÖzçelik, Güven (Arel Author)The characteristics of convective heat transfer and friction factor for periodic corrugated channels are investigated numerically. In the numerical study, the finite volume method (FVM) is used. Three different Reynolds averaged numerical simulation (RANS) based turbulent models, namely the k-omega, the shear stress transport (SST) model and the transition SST model are employed and compared with each other. Experimental results obtained from a previous study are used for the assessment of the numerical results. Investigations are performed for air flowing through corrugated channels with an inclination angle of 30 degrees. The Reynolds number is varied within the range 2,000 to 11,000, while keeping the Prandtl number constant at 0.70. Variations of the Nusselt number, Colburn factor, friction factor and goodness factor with the Reynolds number are studied. Effects of the corrugation geometry and channel height are discussed. The overall performances of the considered turbulence model are observed to be quite similar. The SST model is observed to show a slightly better overall performance
Torsion Angle Effect on the Activation of UiO Metal–Organic Frameworks
No full textWe present a systematic investigation
of the factors influencing
the surface area of zirconium-based UiO-type metal–organic
frameworks (MOFs), revealing an important relationship between factors
including the conformation of the organic linker in the MOF, surface
tension of the guest molecules (solvent), and the stability of MOFs
toward activation (removal of guest molecules). The results obtained
demonstrate how the structure of the linkers forming the isostructural
series of UiO MOFs with fcu topology could alter the resistance and
stability of the MOF frameworks toward capillary force-driven structural
degradation governed by the solvent during activation
Detoxification of a Sulfur Mustard Simulant Using a BODIPY-Functionalized Zirconium-Based Metal–Organic Framework
No full textSystematic Postsynthetic Modification of Nanoporous Organic Frameworks for Enhanced CO2 Capture from Flue Gas and Landfill Gas
No full textControlled postsynthetic nitration of NPOF-1, a nanoporous organic framework constructed by nickel(0)-catalyzed Yamamoto coupling of 1,3,5-tris(4-bromophenyl)benzene, has been performed and is proven to be a promising route to introduce nitro groups and to convert mesopores to micropores without compromising surface area. Reduction of the nitro groups yields aniline-like amine-functionalized NPOF-1-NH2 that has a micropore volume of 0.48 cm3 g–1, which corresponds to 71% of the total pore volume and a Brunauer–Emmett–Teller surface area of 1535 m2 g–1. Adequate basicity of the amine functionalities leads to modest isosteric heats of adsorption for CO2, which allow for high regenerability. The unique combination of high surface area, microporous structure, and amine-functionalized pore walls enables NPOF-1-NH2 to have remarkable CO2 working capacity values for removal from landfill gas and flue gas. The performance of NPOF-1-NH2 in CO2 removal ranks among the best by porous organic materials
Green Synthesis of a Functionalized Zirconium-Based Metal–Organic Framework for Water and Ethanol Adsorption
No full textAqueous synthesis of metal−organic frameworks (MOFs) at room temperature offers many advantages such as reduction in the generation of toxic byproducts and operation costs, as well as increased safety in the material’s production. Functional group-bearing MOFs have received growing attention compared to nonfunctionalized analogues due to enhanced adsorption properties of the former in many cases. Here, we report an aqueous solution-based synthesis of a robust zirconium MOF, UiO-66-NO2, at room temperature. We evaluated the phase purity, porosity, thermal stability, particle morphology and size of the resulting material. High uptake, as well as near complete recyclability of water and ethanol vapor isotherms at room temperature supports the potential of UiO-66-NO2 as a solid adsorbent in adsorption-based cooling applications or water harvesting systems
Torsion Angle Effect on the Activation of UiO Metal-Organic Frameworks
No full textWe present a systematic investigation of the factors influencing the surface area of zirconium-based UiO-type metal-organic frameworks (MOFs), revealing an important relationship between factors including the conformation of the organic linker in the MOF, surface tension of the guest molecules (solvent), and the stability of MOFs toward activation (removal of guest molecules). The results obtained demonstrate how the structure of the linkers forming the isostructural series of UiO MOFs with fcu topology could alter the resistance and stability of the MOF frameworks toward capillary force-driven structural degradation governed by the solvent during activation.</p
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