102,295 research outputs found
Mn-CUK-1: A Flexible MOF for SO<sub>2</sub>, H<sub>2</sub>O, and H<sub>2</sub>S Capture
No full textThe environmentally benign metal-organic framework (MOF)
CUK-1
based on 2,4-pyridine dicarboxylate has been prepared for the first
time using Mn(II) as the inorganic node and water as the only solvent.
Mn-CUK-1 shows reversible and efficient capture of H2O,
SO2, and H2S. Compared to previously studied
Co(II) and Mg(II) versions of the same MOF, Mn-CUK-1 also exhibited
unique temperature-induced structural flexibility due to organic linker
torsion, as detailed by variable-temperature single-crystal X-ray
diffraction studies. Owing to this inherent solid-state flexibility,
Mn-CUK-1 showed stepwise adsorption for polar gases, which induce
structural deformations upon adsorption, while the nonpolar guest
adsorbates were reversibly sorbed in a more classical manner. Notably,
Mn-CUK-1 demonstrates the highest reported H2S capacity-to-surface
area ratio among MOFs that are chemically stable toward this reactive
acidic molecule. Moreover, Mn-CUK-1 displays exceptional structural
stability in the presence of high relative humidity and corrosive
gases and shows soft crystalline behavior triggered by changes in
both the adsorption temperature and guest molecule identity
Reversible Solid-State Isomerism of Azobenzene-Loaded Large-Pore Isoreticular Mg-CUK-1
No full textA large-pore version of Mg-CUK-1, a water-stable metal-organic framework (MOF) with 1-D channels, was synthesized in basic water. Mg-CUK-1L has a BET surface area of 2896 m2 g-1 and shows stark selectivity for CO2 sorption over N2, O2, H2, and CH4. It displays reversible, multistep gated sorption of CO2 below 0.33 atm. The dehydrated single-crystal structure of Mg-CUK-1L confirms retention of the open-channel structure. The MOF can be loaded with organic molecules by immersion in hot melts, providing single crystals suitable for X-ray diffraction. trans-Azobenzene fills the channels in a 2 × 2 arrangement. Solid-state UV-vis spectroscopy reveals that azobenzene molecules undergo reversible trans-cis isomerization, despite being close-packed; this surprising result is confirmed by DFT-simulated UV-vis spectra
Reversible Solid-State Isomerism of Azobenzene-Loaded Large-Pore Isoreticular Mg-CUK‑1
No full textA large-pore version
of Mg-CUK-1, a water-stable metal–organic
framework (MOF) with 1-D channels, was synthesized in basic water.
Mg-CUK-1L has a BET surface area of 2896 m2 g–1 and shows stark selectivity for CO2 sorption over N2, O2, H2, and CH4. It displays
reversible, multistep gated sorption of CO2 below 0.33
atm. The dehydrated single-crystal structure of Mg-CUK-1L confirms
retention of the open-channel structure. The MOF can be loaded with
organic molecules by immersion in hot melts, providing single crystals
suitable for X-ray diffraction. trans-Azobenzene
fills the channels in a 2 × 2 arrangement. Solid-state UV–vis
spectroscopy reveals that azobenzene molecules undergo reversible trans–cis isomerization, despite
being close-packed; this surprising result is confirmed by DFT-simulated
UV–vis spectra
Reversible Solid-State Isomerism of Azobenzene-Loaded Large-Pore Isoreticular Mg-CUK‑1
No full textA large-pore version
of Mg-CUK-1, a water-stable metal–organic
framework (MOF) with 1-D channels, was synthesized in basic water.
Mg-CUK-1L has a BET surface area of 2896 m2 g–1 and shows stark selectivity for CO2 sorption over N2, O2, H2, and CH4. It displays
reversible, multistep gated sorption of CO2 below 0.33
atm. The dehydrated single-crystal structure of Mg-CUK-1L confirms
retention of the open-channel structure. The MOF can be loaded with
organic molecules by immersion in hot melts, providing single crystals
suitable for X-ray diffraction. trans-Azobenzene
fills the channels in a 2 × 2 arrangement. Solid-state UV–vis
spectroscopy reveals that azobenzene molecules undergo reversible trans–cis isomerization, despite
being close-packed; this surprising result is confirmed by DFT-simulated
UV–vis spectra
Reversible Solid-State Isomerism of Azobenzene-Loaded Large-Pore Isoreticular Mg-CUK‑1
No full textA large-pore version
of Mg-CUK-1, a water-stable metal–organic
framework (MOF) with 1-D channels, was synthesized in basic water.
Mg-CUK-1L has a BET surface area of 2896 m2 g–1 and shows stark selectivity for CO2 sorption over N2, O2, H2, and CH4. It displays
reversible, multistep gated sorption of CO2 below 0.33
atm. The dehydrated single-crystal structure of Mg-CUK-1L confirms
retention of the open-channel structure. The MOF can be loaded with
organic molecules by immersion in hot melts, providing single crystals
suitable for X-ray diffraction. trans-Azobenzene
fills the channels in a 2 × 2 arrangement. Solid-state UV–vis
spectroscopy reveals that azobenzene molecules undergo reversible trans–cis isomerization, despite
being close-packed; this surprising result is confirmed by DFT-simulated
UV–vis spectra
Reversible Solid-State Isomerism of Azobenzene-Loaded Large-Pore Isoreticular Mg-CUK‑1
No full textA large-pore version
of Mg-CUK-1, a water-stable metal–organic
framework (MOF) with 1-D channels, was synthesized in basic water.
Mg-CUK-1L has a BET surface area of 2896 m2 g–1 and shows stark selectivity for CO2 sorption over N2, O2, H2, and CH4. It displays
reversible, multistep gated sorption of CO2 below 0.33
atm. The dehydrated single-crystal structure of Mg-CUK-1L confirms
retention of the open-channel structure. The MOF can be loaded with
organic molecules by immersion in hot melts, providing single crystals
suitable for X-ray diffraction. trans-Azobenzene
fills the channels in a 2 × 2 arrangement. Solid-state UV–vis
spectroscopy reveals that azobenzene molecules undergo reversible trans–cis isomerization, despite
being close-packed; this surprising result is confirmed by DFT-simulated
UV–vis spectra
Reversible Solid-State Isomerism of Azobenzene-Loaded Large-Pore Isoreticular Mg-CUK‑1
No full textA large-pore version
of Mg-CUK-1, a water-stable metal–organic
framework (MOF) with 1-D channels, was synthesized in basic water.
Mg-CUK-1L has a BET surface area of 2896 m2 g–1 and shows stark selectivity for CO2 sorption over N2, O2, H2, and CH4. It displays
reversible, multistep gated sorption of CO2 below 0.33
atm. The dehydrated single-crystal structure of Mg-CUK-1L confirms
retention of the open-channel structure. The MOF can be loaded with
organic molecules by immersion in hot melts, providing single crystals
suitable for X-ray diffraction. trans-Azobenzene
fills the channels in a 2 × 2 arrangement. Solid-state UV–vis
spectroscopy reveals that azobenzene molecules undergo reversible trans–cis isomerization, despite
being close-packed; this surprising result is confirmed by DFT-simulated
UV–vis spectra
Three-phase single stage medium power supply using Cuk converter
No full textA three-phase ac mains fed single stage medium power SMPS (Switched Mode Power Supply) is designed and modeled using dc-dc Cuk converter modules. The ac supply feeds to the modules of power supply, which are connected in series at the output to increase its rating and balancing the power on all three phases of supply. High frequency isolated Cuk converters are used as modular dc-dc converter in discontinuous conduction mode (DCM) of operation for power factor correction (PFC). Nearly unity power factor (PF) operation in the proposed power supply is obtained with harmonic reduction at three-phase input ac mains. Power quality indices of the power supply are also presented to demonstrate its improved performance at varying loading conditions
Fractional order PID controlled hybrid Cuk converter for electric vehicle
No full textChoosing the right controller with the right approach is one of any power converter's biggest concerns. In order to optimise induction heating, a hybrid Cuk converter with a fractional-order proportional integral derivative (FOPID) controller is built. The findings show an improved time domain responsiveness in the FOPID controlled closed-loop hybrid DC-DC converter (CDHC) system. In order to improve the interface between the resonant inverter and DC source and to step up voltage with less output ripple, Cuk converters are used. The research project is concerned with modelling and simulating a hybrid closed-loop DC converter system. The findings show an improved time domain responsiveness in the FOPID controlled CDHC system. The suggested approach offers advantages such as high-power density and buck boost capability. After being inverted, the Cuk converter's output is applied to a DC load. The time responses of the closed loop proportional integral (PI) and FOPID controlled homogeneous charge compression ignition (HCCI) systems are compared. The hardware is implemented and tested for the CDHC system for electric vehicles. The results indicate that the FOPID controlled CDHC system has enhanced time response and benefits such as high-power density buck boost ability
Investigating H2 Adsorption in Isostructural Metal Organic Frameworks M CUK 1 M Co and Mg through Experimental and Theoretical Studies
No full textA combined experimental and theoretical study of H2 adsorption was carried out in Co CUK 1 and Mg CUK 1, two isostructural metal organic frameworks MOFs that consist of M2 ions M Co and Mg coordinated to pyridine 2,4 dicarboxylate pdc2 and OH ligands. These MOFs possess saturated metal centers in distorted octahedral environments and narrow pore sizes and display high chemical and thermal stability. Previous experimental studies revealed that Co CUK 1 exhibits a H2 uptake of 183 cm3 g 1 at 77 K 1.0 atm [ Angew. Chem., Int. Ed. 2007, 46, 272 amp; 8722;275, DOI 10.1002 anie.200601627], while that for Mg CUK 1 under the same conditions is 240 cm3 g 1 on the basis of the experimental measurements carried out herein. The theoretical H2 adsorption isotherms are in close agreement with the corresponding experimental measurements for simulations using electrostatic and polarizable potentials of the adsorbate. Through simulated annealing calculations, it was found that the primary binding site for H2 in both isostructural analogues is localized proximal to the center of the aromatic rings belonging to the pdc2 linkers. Inelastic neutron scattering INS spectroscopic studies of H2 adsorbed in both MOFs revealed a rotational tunnelling transition occurring at around 8 meV in the corresponding spectra; this peak represents H2 adsorbed at the primary binding site. Two dimensional quantum rotation calculations for H2 localized at the primary and secondary binding sites in both MOFs yielded rotational energy levels that are in agreement with the transitions observed in the INS spectra. Even though both M CUK 1 analogues possess different metal ions, they exhibit similar electrostatic environments, modeled structures at H2 saturation, and rotational potentials for H2 adsorbed at the most favorable adsorption site. Overall, this study demonstrates how important molecular level details of the H2 adsorption mechanism inside MOF micropores can be derived from a combination of experimental measurements and theoretical calculations using two stable and isostructural MOFs with saturated metal centers and small pore windows as model system
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