Density Functional Theory Calculation and X-ray Absorption Spectroscopy Studies of Structure of Vanadium-Containing Aluminophosphate VAPO-5

Cheng, H. S.; Yang, E.; Lai, Chin‐Hung; Chao, Kuei‐Hsiang; Wei, A.C.; Lee, J.F.

doi:10.1021/jp993981e

Cited by 15 publications

(17 citation statements)

References 34 publications

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“…19,20,36,37 A major source of complexity associated with studying VAPOs is the vanadium ion's ability not only to adopt different oxidation states, but also to occupy both framework and extraframework positions. Furthermore, V ions in solution can give rise to oligomerisation and yield polynuclear clusters.…”

Section: 263334mentioning

confidence: 99%

“…The structure of V ions in AlPOs frameworks is still the subject of an open debate, due to the complex chemistry and coordinative flexibility of the oxovanadium species (V 4+ O or V 5+ O vanadyls), the vanadyl ion being the usual source of vanadium in the VAPO synthesis. ,,, A major source of complexity associated with studying VAPOs is the vanadium ion’s ability not only to adopt different oxidation states but also to occupy both framework and extraframework positions. Furthermore, V ions in solution can give rise to oligomerization and yield polynuclear clusters.…”

Section: Introductionmentioning

confidence: 99%

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Structure of the Catalytic Active Sites in Vanadium-Doped Aluminophosphate Microporous Materials. New Evidence from Spin Density Studies

et al. 2014

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Section: 263334mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Structure of the Catalytic Active Sites in Vanadium-Doped Aluminophosphate Microporous Materials. New Evidence from Spin Density Studies

et al. 2014

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“…The attempts to optimize representative ring type clusters for each of the structures investigated in this study, following a procedure similar to that described by Cheng et al, 34 was unsuccessful. Here we present the optimized structures derived from the SOD framework, for which all possible rings were investigated.…”

Section: Appendix Amentioning

confidence: 99%

“…The calculated clusters indicated that while the substitution of either P or Al in the framework is not feasible, the parameters of optimized models representing an extraframework substitution site are comparable with those obtained from the in-situ X-ray absorption experiments. 34 In this paper we have examined, using high-field EPR techniques, three Mn(II) incorporated aluminophosphate structures (Mn-AlPO 4 -20, Mn-AlPO 4 -5, and Mn-AlPO 4 -11), two new frameworks composed of magnesium-aluminophosphate with large open cages 8 (Mn-UCSB-6Mg and Mn-UCSB-10Mg) and one example of Fe(III) incorporated into aluminophosphate zeotype (Fe-AlPO 4 -20). These framework structures are schematically presented in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

Isomorphous Substitution of Mn(II) into Aluminophosphate Zeotypes: A Combined High-Field ENDOR and DFT Study

et al. 2002

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The incorporation of low levels of Mn(II) (Mn/Al∼0.001) into five aluminophosphate zeotypes was studied by high-field echo-detected EPR, and by 31P and 1H electron−nuclear double resonance (ENDOR) spectroscopies. The zeotype structures investigatedSOD, AEL, AFI, SBS, and SBTcover a variety of channel morphologies, and span a range of framework densities. The highly resolved EPR spectra could distinguish between two types of Mn with different 55Mn hyperfine couplings in structures containing more than one T site. Mims and Davies 31P ENDOR spectra, recorded at a field set to one of the |−/2, m I 〉 → |+1/2, m I 〉 55Mn hyperfine components consist of a symmetric doublet, with a splitting in the range of 5−8 MHz. The large open structures showed smaller couplings than the denser morphologies. A similar 31P hyperfine was also detected for Fe(III) incorporated into aluminophosphate zeotype with the SOD structure. Variations in the 1H ENDOR spectra of the various Mn(II) substituted zeotypes, particularly in the relative intensity of the 1H matrix line, were detected as well. These ENDOR results indicate a common mechanism of framework substitution in which Mn(II) and Fe(III) are replacing Al (or Mg). Moreover, the spectra serve as a probe for the differences in the local environment and bonding topology of these substituted framework sites. A qualitative interpretation of the 31P ENDOR data is provided, based on relevant crystallographic information, and the 1H ENDOR signals are partially attributed to the interactions with the templates occluded in the zeotype cages. To further relate the isotropic 31P hyperfine couplings to structural properties, DFT methods were employed for cluster model optimizations and hyperfine coupling constants calculations. Geometry optimizations of substituted rings, derived from the SOD and AEL framework structures, indicate considerable distortions of the coordination environment of framework Mn as compared to Al. A systematic study of the hyperfine interactions of a series of model structures containing tetrahedral and octahedral Mn(II) show that both Mn−O bond lengths and Mn−O−P bond angles contribute significantly to the variation in the isotropic and anisotropic 31P hyperfine coupling.

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“…18 Padlyak et al showed framework incorporation of the Cr 3+ ions only for CrAPO-5 with high sorption properties. 19 We have studied the structure of a vanadium-containing aluminophosphate-5 molecular sieve (VAPO-5) using the density functional theory (DFT) 20 calculations combined with in-situ XAS 21 and Raman Spectroscopy 22 previously. Results have shown that the substitution of the aluminum or phosphorous site of an AFI framework by vanadium is in general not feasible.…”

Section: +mentioning

confidence: 99%

Study on Chromium‐Containing Aluminophosphate CrAPO‐5 via Density Functional Theory

Cheng

Chang

2008

J Chinese Chemical Soc

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Various structures of CrAPO-5 clusters are studied via density functional B3LYP exchange-correlation method. The optimized structures are compared with data from X-ray absorption. Their total energies and atomic net charges are also analyzed. Results indicate that the substitution of the aluminum site of an AFI framework by chromium is in general not feasible. The chromium ion is more likely docked in between two neighboring 12-membered rings of the framework of AFI. To further verify our claim, the excitation energies of the representative chromium structures of CrAPO-5 clusters are calculated via the TDDFT method. The results for excitation energies further support that Cr 3+ is not incorporated into the framework.

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Density Functional Theory Calculation and X-ray Absorption Spectroscopy Studies of Structure of Vanadium-Containing Aluminophosphate VAPO-5

Cited by 15 publications

References 34 publications

Structure of the Catalytic Active Sites in Vanadium-Doped Aluminophosphate Microporous Materials. New Evidence from Spin Density Studies

Structure of the Catalytic Active Sites in Vanadium-Doped Aluminophosphate Microporous Materials. New Evidence from Spin Density Studies

Isomorphous Substitution of Mn(II) into Aluminophosphate Zeotypes: A Combined High-Field ENDOR and DFT Study

Study on Chromium‐Containing Aluminophosphate CrAPO‐5 via Density Functional Theory

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