Abstract:Zeolites
with appropriately narrow pore apertures can kinetically
enhance the selective adsorption of CO
2
over N
2
. Here, we showed that the exchangeable cations (e.g., Na
+
or K
+
) on zeolite ZK-4 play an important role in the
CO
2
selectivity. Zeolites NaK ZK-4 with Si/Al = 1.8–2.8
had very high CO
2
selectivity when an intermediate number
of the exchangeable cations we… Show more
“…This procedure employs high-resolution 7 Li– 7 Li correlation MAS NMR spectroscopy coupled with periodic DFT calculations of the structure of Li + sites and subsequent DFT cluster computations of the 7 Li NMR shielding. Similarly, 23 Na solid-state NMR spectroscopy represents a powerful tool to identify the Na + siting in matrices of Si-rich zeolites. , The incorporation of Na + cations into diverse matrices has attracted particular attention because of its pivotal importance in various fields such as, for example, energy storage and CO 2 capture. − …”
Section: Introductionmentioning
confidence: 99%
“…17,18 The incorporation of Na + cations into diverse matrices has attracted particular attention because of its pivotal importance in various fields such as, for example, energy storage 19 and CO 2 capture. 20 In this paper, we demonstrate a new approach to the determination of the siting of Na + and the local structure of Na + extra-framework cationic sites in crystalline aluminosilicate matrices based on a combination of high-field and ultra-highfield MAS and MQMAS 23 Na NMR spectroscopy interpreted using predictions of the 23 Na NMR parameters obtained from periodic DFT calculations including extensive molecular dynamics (MD) simulations. The usage of high-field and ultra-high-field 23 Na solid-state NMR permits highly reliable evaluations of the 23 Na NMR parameters of Na + cations in various cationic sites.…”
Section: Introductionmentioning
confidence: 99%
“…20 In this paper, we demonstrate a new approach to the determination of the siting of Na + and the local structure of Na + extra-framework cationic sites in crystalline aluminosilicate matrices based on a combination of high-field and ultra-highfield MAS and MQMAS 23 Na NMR spectroscopy interpreted using predictions of the 23 Na NMR parameters obtained from periodic DFT calculations including extensive molecular dynamics (MD) simulations. The usage of high-field and ultra-high-field 23 Na solid-state NMR permits highly reliable evaluations of the 23 Na NMR parameters of Na + cations in various cationic sites. While 23 Na MAS NMR spectroscopy is used to identify Na + cations with a large quadrupolar broadening since the 23 Na NMR resonances of such cations are suppressed in 23 Na MQMAS NMR experiments, 23 Na MQMAS NMR experiments are employed to analyze close overlapping 23 Na NMR resonances with a smaller quadrupolar broadening.…”
Section: Introductionmentioning
confidence: 99%
“…The usage of high-field and ultra-high-field 23 Na solid-state NMR permits highly reliable evaluations of the 23 Na NMR parameters of Na + cations in various cationic sites. While 23 Na MAS NMR spectroscopy is used to identify Na + cations with a large quadrupolar broadening since the 23 Na NMR resonances of such cations are suppressed in 23 Na MQMAS NMR experiments, 23 Na MQMAS NMR experiments are employed to analyze close overlapping 23 Na NMR resonances with a smaller quadrupolar broadening. The results reveal that Na + cations can be ligated to oxygen atoms of nine distinct extra-framework cationic sites of which eight are occupied by Na + in one or more of the investigated samples.…”
Section: Introductionmentioning
confidence: 99%
“…The occupation of the Na + cationic sites is not controlled by their relative energies but by the kinetics of the Na + ion-exchange. 23 Na solid-state NMR spectroscopy alone can determine the ring forming the Na + site but not which T site is occupied by Al in that ring. The developed methodology represents a highly promising tool for the analysis of the Na + arrangements in zeolites and other crystalline matrices.…”
Zeolites
are crystalline microporous aluminosilicates of paramount
importance. The siting of cations balancing the negative charge of
framework Al affects the catalytic and sorption properties of cation-exchanged
zeolites. The siting of Na+ cations in dehydrated Si-rich
ferrierite zeolites is investigated by 23Na (ultra)-high-field
(MQ)MAS NMR spectroscopy together with DFT to obtain the Na+ siting and the local structure of nine Na+ cationic sites
formed by two 6-rings and two 8-rings having one Al atom located in
different framework T sites. The occupation of the Na+ cationic
sites is not controlled by their relative energies but by the kinetics
of the Na+ ion-exchange. 23Na solid-state NMR
spectroscopy alone can determine the ring forming the Na+ site but not which T site is occupied by Al in that ring. The developed
methodology represents a highly promising tool for the analysis of
the Na+ arrangements in zeolites and other crystalline
matrices.
“…This procedure employs high-resolution 7 Li– 7 Li correlation MAS NMR spectroscopy coupled with periodic DFT calculations of the structure of Li + sites and subsequent DFT cluster computations of the 7 Li NMR shielding. Similarly, 23 Na solid-state NMR spectroscopy represents a powerful tool to identify the Na + siting in matrices of Si-rich zeolites. , The incorporation of Na + cations into diverse matrices has attracted particular attention because of its pivotal importance in various fields such as, for example, energy storage and CO 2 capture. − …”
Section: Introductionmentioning
confidence: 99%
“…17,18 The incorporation of Na + cations into diverse matrices has attracted particular attention because of its pivotal importance in various fields such as, for example, energy storage 19 and CO 2 capture. 20 In this paper, we demonstrate a new approach to the determination of the siting of Na + and the local structure of Na + extra-framework cationic sites in crystalline aluminosilicate matrices based on a combination of high-field and ultra-highfield MAS and MQMAS 23 Na NMR spectroscopy interpreted using predictions of the 23 Na NMR parameters obtained from periodic DFT calculations including extensive molecular dynamics (MD) simulations. The usage of high-field and ultra-high-field 23 Na solid-state NMR permits highly reliable evaluations of the 23 Na NMR parameters of Na + cations in various cationic sites.…”
Section: Introductionmentioning
confidence: 99%
“…20 In this paper, we demonstrate a new approach to the determination of the siting of Na + and the local structure of Na + extra-framework cationic sites in crystalline aluminosilicate matrices based on a combination of high-field and ultra-highfield MAS and MQMAS 23 Na NMR spectroscopy interpreted using predictions of the 23 Na NMR parameters obtained from periodic DFT calculations including extensive molecular dynamics (MD) simulations. The usage of high-field and ultra-high-field 23 Na solid-state NMR permits highly reliable evaluations of the 23 Na NMR parameters of Na + cations in various cationic sites. While 23 Na MAS NMR spectroscopy is used to identify Na + cations with a large quadrupolar broadening since the 23 Na NMR resonances of such cations are suppressed in 23 Na MQMAS NMR experiments, 23 Na MQMAS NMR experiments are employed to analyze close overlapping 23 Na NMR resonances with a smaller quadrupolar broadening.…”
Section: Introductionmentioning
confidence: 99%
“…The usage of high-field and ultra-high-field 23 Na solid-state NMR permits highly reliable evaluations of the 23 Na NMR parameters of Na + cations in various cationic sites. While 23 Na MAS NMR spectroscopy is used to identify Na + cations with a large quadrupolar broadening since the 23 Na NMR resonances of such cations are suppressed in 23 Na MQMAS NMR experiments, 23 Na MQMAS NMR experiments are employed to analyze close overlapping 23 Na NMR resonances with a smaller quadrupolar broadening. The results reveal that Na + cations can be ligated to oxygen atoms of nine distinct extra-framework cationic sites of which eight are occupied by Na + in one or more of the investigated samples.…”
Section: Introductionmentioning
confidence: 99%
“…The occupation of the Na + cationic sites is not controlled by their relative energies but by the kinetics of the Na + ion-exchange. 23 Na solid-state NMR spectroscopy alone can determine the ring forming the Na + site but not which T site is occupied by Al in that ring. The developed methodology represents a highly promising tool for the analysis of the Na + arrangements in zeolites and other crystalline matrices.…”
Zeolites
are crystalline microporous aluminosilicates of paramount
importance. The siting of cations balancing the negative charge of
framework Al affects the catalytic and sorption properties of cation-exchanged
zeolites. The siting of Na+ cations in dehydrated Si-rich
ferrierite zeolites is investigated by 23Na (ultra)-high-field
(MQ)MAS NMR spectroscopy together with DFT to obtain the Na+ siting and the local structure of nine Na+ cationic sites
formed by two 6-rings and two 8-rings having one Al atom located in
different framework T sites. The occupation of the Na+ cationic
sites is not controlled by their relative energies but by the kinetics
of the Na+ ion-exchange. 23Na solid-state NMR
spectroscopy alone can determine the ring forming the Na+ site but not which T site is occupied by Al in that ring. The developed
methodology represents a highly promising tool for the analysis of
the Na+ arrangements in zeolites and other crystalline
matrices.
Herein, we have designed and synthesized two heteroatom (N, O) rich covalent organic frameworks (COF), PD-COF and TF-COF, respectively, to demonstrate their relative effect on CO 2 adsorption capacity and also CO 2 /N 2 selectivity. Compared to the non-fluorinated PD-COF (BET surface area 805 m 2 g À 1 , total pore volume 0.3647 ccg À 1 ), a decrease in BET surface area and also pore volume have been observed for fluorinated TF-COF due to the incorporation of fluorine to the porous framework (BET surface area 451 m 2 g À 1 , total pore volume 0.2978 ccg À 1 ). This fact leads to an enormous decrease in the CO 2 adsorption capacity and CO 2 /N 2 selectivity of TF-COF, though it shows stronger affinity towards CO 2 with a Qst of 37.76 KJ/mol. The more CO 2 adsorption capacity by PD-COF can be attributed to the large specific surface area with considerable amount of micropore volume compared to the TF-COF. Further, PD-COF exhibited CO 2 /N 2 selectivity of 16.8, higher than that of TF-COF (CO 2 /N 2 selectivity 13.4).
A strategy of tuning azole‐based ionic liquids for reversible CO2 capture from ambient air was reported. Through tuning the basicity of anion as well as the type of cation, an ideal azole‐based ionic liquid with both high CO2 capacity and excellent stability was synthesized, which exhibited a highest single‐component isotherm uptake of 2.17 mmol/g at the atmospheric CO2 concentration of 0.4 mbar at 30 oC, even in the presence of water. The bound CO2 can be released by relatively mild heating of the IL‐CO2 at 80 oC, which mike it promising for energy‐efficient CO2 desorption and sorbent regeneration, leading to excellent reversibility. To the best of our knowledge, these azole‐based ionic liquids are superior to other adsorbent materials for direct air capture due to their dual‐tunable properties and high CO2 capture efficiency, offering a new prospect for efficient and reversible direct air capture technologies.
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