20 research outputs found
Correlated Multimodal Approach Reveals Key Details of Nerve-Agent Decomposition by Single-Site Zr-Based Polyoxometalates
Development of technologies for protection against chemical warfare agents (CWAs) is critically important. Recently, polyoxometalates have attracted attention as potential catalysts for nerve-agent decomposition. Improvement of their effectiveness in real operating conditions requires an atomic-level understanding of CWA decomposition at the gas–solid interface. We investigated decomposition of the nerve agent Sarin and its simulant, dimethyl chlorophosphate (DMCP), by zirconium polytungstate. Using a multimodal approach, we showed that upon DMCP and Sarin exposure the dimeric tungstate undergoes monomerization, making coordinatively unsaturated Zr(IV) centers available, which activate nucleophilic hydrolysis. Further, DMCP is shown to be a good model system of reduced toxicity for studies of CWA deactivation at the gas–solid interface
A concept "bank laws" in a wide and narrow value
Досліджено сутність поняття “банківське законодавство” в широкому і вузькому значенні.Essence of concept "bank laws" in a wide and narrow value is investigated
Modeling Gas Flow Dynamics in Metal–Organic Frameworks
Modeling
fluid flow dynamics in metal organic frameworks (MOFs)
is a required step toward understanding mechanisms of their activity
as novel catalysts, sensors, and filtration materials. We adapted
a lattice Boltzmann model, previously used for studying flow dynamics
in meso- and microporous media, to the nanoscale dimensions of the
MOF pores. Using this model, rapid screening of permeability of a
large number of MOF structures, in different crystallographic directions,
is possible. The method was illustrated here on the example of an
anisotropic MOF, for which we calculated permeability values in different
flow directions. This method can be generalized to a large class of
MOFs and used to design MOFs with the desired gas flow permeabilities
Synthesis, Structures and Photoluminescence Properties of a Series of Alkaline Earth Metal-Based Coordination Networks Synthesized Using Thiophene-Based Linkers
Three new 3-D coordination networks were synthesized
using alkaline-earth
metal centers, calcium, and strontium, with 2,5-thiophenedicarboxylate
(TDC) as the organic linker. [Ca<sub>2</sub>(TDC-2H)<sub>2</sub>(DMF)<sub>2</sub>]<sub><i>n</i></sub> [<b>1</b>, space group <i>P</i>2<sub>1</sub>/<i>n</i>, <i>a</i> =
10.0704(3) Å, <i>b</i> = 14.2521(3) Å, <i>c</i> = 17.5644(6) Å, β = 94.281(2)°] is composed
of tetrameric calcium polyhedral clusters, which are connected by
the organic linkers. Coordinated DMF molecules are present within
the 1-D channel along the [010] direction. [Ca(TDC-2H)]<sub><i>n</i></sub> [<b>2</b>, space group <i>Pbcm</i>, <i>a</i> = 5.3331(5) Å, <i>b</i> = 6.8981(4)
Å, <i>c</i> = 18.141(2) Å] consists of chains
of edge-sharing calcium octahedra, connected by organic linkers, to
form a dense network. [Sr(TDC-2H)(DMF)]<sub><i>n</i></sub> [<b>3</b>, space group <i>P</i>2<sub>1</sub>/<i>n</i>, <i>a</i> = 5.9795(3) Å, <i>b</i> = 17.058(1) Å, <i>c</i> = 11.3592(6) Å, β
= 91.257(1)°] forms a structural topology almost identical to
compound <b>1</b> except that the chains are built by combinations
of edge- and face-sharing polyhedra. Compounds <b>1</b> and <b>3</b> were synthesized using DMF as solvent, whereas compound <b>2</b> crystallizes using ethanol. Photoluminescence studies reveal
that the topologies of the networks and the presence of the coordinated
solvent molecules control the luminescence properties of the compounds
Synthesis, Structures and Photoluminescence Properties of a Series of Alkaline Earth Metal-Based Coordination Networks Synthesized Using Thiophene-Based Linkers
Three new 3-D coordination networks were synthesized
using alkaline-earth
metal centers, calcium, and strontium, with 2,5-thiophenedicarboxylate
(TDC) as the organic linker. [Ca<sub>2</sub>(TDC-2H)<sub>2</sub>(DMF)<sub>2</sub>]<sub><i>n</i></sub> [<b>1</b>, space group <i>P</i>2<sub>1</sub>/<i>n</i>, <i>a</i> =
10.0704(3) Å, <i>b</i> = 14.2521(3) Å, <i>c</i> = 17.5644(6) Å, β = 94.281(2)°] is composed
of tetrameric calcium polyhedral clusters, which are connected by
the organic linkers. Coordinated DMF molecules are present within
the 1-D channel along the [010] direction. [Ca(TDC-2H)]<sub><i>n</i></sub> [<b>2</b>, space group <i>Pbcm</i>, <i>a</i> = 5.3331(5) Å, <i>b</i> = 6.8981(4)
Å, <i>c</i> = 18.141(2) Å] consists of chains
of edge-sharing calcium octahedra, connected by organic linkers, to
form a dense network. [Sr(TDC-2H)(DMF)]<sub><i>n</i></sub> [<b>3</b>, space group <i>P</i>2<sub>1</sub>/<i>n</i>, <i>a</i> = 5.9795(3) Å, <i>b</i> = 17.058(1) Å, <i>c</i> = 11.3592(6) Å, β
= 91.257(1)°] forms a structural topology almost identical to
compound <b>1</b> except that the chains are built by combinations
of edge- and face-sharing polyhedra. Compounds <b>1</b> and <b>3</b> were synthesized using DMF as solvent, whereas compound <b>2</b> crystallizes using ethanol. Photoluminescence studies reveal
that the topologies of the networks and the presence of the coordinated
solvent molecules control the luminescence properties of the compounds
Structural Chemistry of Akdalaite, Al<sub>10</sub>O<sub>14</sub>(OH)<sub>2</sub>, the Isostructural Aluminum Analogue of Ferrihydrite
As part of an effort to characterize clusters and intermediate phases likely to be encountered along solution reaction pathways that produce iron and aluminum oxide-hydroxides from Fe and Al precursors, the complete structure of Al10O14(OH)2 (akdalaite) was determined from a combination of single-crystal X-ray diffraction (SC-XRD) data collected at 100 K to define the Al and O positions, and solid-state nuclear magnetic resonance (NMR) and neutron powder diffraction (NPD) data collected at room temperature (~300 K) to precisely determine the nature of hydrogen in the structure. Two different synthesis routes produced different crystal morphologies. Using an aluminum oxyhydroxide floc made from mixing AlCl3 and 0.48 M NaOH, the product had uniform needle morphology, while using nanocrystalline boehmite (Vista Chemical Company Catapal D alumina) as the starting material produced hexagonal plates. Akdalaite crystallizes in the space group P63mc with lattice parameters of a = 5.6244(3) Å and c = 8.8417(3) Å (SC-XRD) and a = 5.57610(2) Å and c = 8.77247(6) Å (NPD). The crystal structure features Al13O40 Keggin clusters. The structural chemistry of akdalaite is nonideal but broadly conforms to that of ferrihydrite, the nanomineral with which it is isostructural
A Calcium Coordination Framework Having Permanent Porosity and High CO<sub>2</sub>/N<sub>2</sub> Selectivity
A thermally stable, microporous calcium coordination
network shows
a reversible 5.75 wt % CO<sub>2</sub> uptake at 273 K and 1 atm pressure,
with an enthalpy of interaction of ∼31 kJ/mol and a CO<sub>2</sub>/N<sub>2</sub> selectivity over 45 under ideal flue gas conditions.
The absence of open metal sites in the activated material suggests
a different mechanism for selectivity and high interaction energy
compared to those for frameworks with open metal sites
A Calcium Coordination Framework Having Permanent Porosity and High CO<sub>2</sub>/N<sub>2</sub> Selectivity
A thermally stable, microporous calcium coordination
network shows
a reversible 5.75 wt % CO<sub>2</sub> uptake at 273 K and 1 atm pressure,
with an enthalpy of interaction of ∼31 kJ/mol and a CO<sub>2</sub>/N<sub>2</sub> selectivity over 45 under ideal flue gas conditions.
The absence of open metal sites in the activated material suggests
a different mechanism for selectivity and high interaction energy
compared to those for frameworks with open metal sites
A Calcium Coordination Framework Having Permanent Porosity and High CO<sub>2</sub>/N<sub>2</sub> Selectivity
A thermally stable, microporous calcium coordination
network shows
a reversible 5.75 wt % CO<sub>2</sub> uptake at 273 K and 1 atm pressure,
with an enthalpy of interaction of ∼31 kJ/mol and a CO<sub>2</sub>/N<sub>2</sub> selectivity over 45 under ideal flue gas conditions.
The absence of open metal sites in the activated material suggests
a different mechanism for selectivity and high interaction energy
compared to those for frameworks with open metal sites