First-Principles Study of AlPO4-H3, a Hydrated Aluminophosphate Zeotype Containing Two Different Types of Adsorbed Water Molecules
Porous aluminophosphate zeotypes (AlPOs) are promising materials for heat transformation applications using water as a working fluid. Two “types” of adsorbed water molecules can be distinguished in hydrated AlPOs: Water molecules adsorbed in the direct proximity of framework alum...
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| Format: | Article |
| Language: | English |
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MDPI AG
2019-03-01
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| Series: | Molecules |
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| Online Access: | http://www.mdpi.com/1420-3049/24/5/922 |
| _version_ | 1811336120938528768 |
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| author | Michael Fischer |
| author_facet | Michael Fischer |
| author_sort | Michael Fischer |
| collection | DOAJ |
| description | Porous aluminophosphate zeotypes (AlPOs) are promising materials for heat transformation applications using water as a working fluid. Two “types” of adsorbed water molecules can be distinguished in hydrated AlPOs: Water molecules adsorbed in the direct proximity of framework aluminium atoms form bonds to these Al atoms, with the coordination number of Al increasing from four to five or six. The remaining water molecules that are adsorbed in other parts of the accessible pore space are not strongly bonded to any framework atom, they interact with their environment exclusively through hydrogen bonds. The APC-type small-pore aluminophosphate AlPO4-H3 contains both types of H2O molecules. In the present work, this prototypical hydrated AlPO is studied using dispersion-corrected density functional theory (DFT) calculations. After validating the computations against experimental crystal structure and Raman spectroscopy data, three interrelated aspects are addressed: First, calculations for various partially hydrated models are used to establish that such partially hydrated phases are not thermodynamically stable, as the interaction with the adsorbed water molecules is distinctly weaker than in fully hydrated AlPO4-H3. Second, IR and Raman spectra are computed and compared to those of the dehydrated analogue AlPO4-C, leading to the identification of a few “fingerprint” modes that could be used as indicators for the presence of Al-coordinated water molecules. Finally, DFT-based molecular dynamics calculations are employed to study the dynamics of the adsorbed water molecules. All in all, this in-depth computational study of AlPO4-H3 contributes to the fundamental understanding of hydrated AlPOs, and should therefore provide valuable information for future computational and experimental studies of these systems. |
| first_indexed | 2024-04-13T17:34:47Z |
| format | Article |
| id | doaj.art-0e1c5189c8644e67a33cadc3be39c0a8 |
| institution | Directory Open Access Journal |
| issn | 1420-3049 |
| language | English |
| last_indexed | 2024-04-13T17:34:47Z |
| publishDate | 2019-03-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Molecules |
| spelling | doaj.art-0e1c5189c8644e67a33cadc3be39c0a82022-12-22T02:37:24ZengMDPI AGMolecules1420-30492019-03-0124592210.3390/molecules24050922molecules24050922First-Principles Study of AlPO4-H3, a Hydrated Aluminophosphate Zeotype Containing Two Different Types of Adsorbed Water MoleculesMichael Fischer0Crystallography Group, Department of Geosciences, University of Bremen, Klagenfurter Straße 2-4, D 28359 Bremen, GermanyPorous aluminophosphate zeotypes (AlPOs) are promising materials for heat transformation applications using water as a working fluid. Two “types” of adsorbed water molecules can be distinguished in hydrated AlPOs: Water molecules adsorbed in the direct proximity of framework aluminium atoms form bonds to these Al atoms, with the coordination number of Al increasing from four to five or six. The remaining water molecules that are adsorbed in other parts of the accessible pore space are not strongly bonded to any framework atom, they interact with their environment exclusively through hydrogen bonds. The APC-type small-pore aluminophosphate AlPO4-H3 contains both types of H2O molecules. In the present work, this prototypical hydrated AlPO is studied using dispersion-corrected density functional theory (DFT) calculations. After validating the computations against experimental crystal structure and Raman spectroscopy data, three interrelated aspects are addressed: First, calculations for various partially hydrated models are used to establish that such partially hydrated phases are not thermodynamically stable, as the interaction with the adsorbed water molecules is distinctly weaker than in fully hydrated AlPO4-H3. Second, IR and Raman spectra are computed and compared to those of the dehydrated analogue AlPO4-C, leading to the identification of a few “fingerprint” modes that could be used as indicators for the presence of Al-coordinated water molecules. Finally, DFT-based molecular dynamics calculations are employed to study the dynamics of the adsorbed water molecules. All in all, this in-depth computational study of AlPO4-H3 contributes to the fundamental understanding of hydrated AlPOs, and should therefore provide valuable information for future computational and experimental studies of these systems.http://www.mdpi.com/1420-3049/24/5/922zeolitesadsorptiondensity functional theorymolecular dynamicscrystallography |
| spellingShingle | Michael Fischer First-Principles Study of AlPO4-H3, a Hydrated Aluminophosphate Zeotype Containing Two Different Types of Adsorbed Water Molecules Molecules zeolites adsorption density functional theory molecular dynamics crystallography |
| title | First-Principles Study of AlPO4-H3, a Hydrated Aluminophosphate Zeotype Containing Two Different Types of Adsorbed Water Molecules |
| title_full | First-Principles Study of AlPO4-H3, a Hydrated Aluminophosphate Zeotype Containing Two Different Types of Adsorbed Water Molecules |
| title_fullStr | First-Principles Study of AlPO4-H3, a Hydrated Aluminophosphate Zeotype Containing Two Different Types of Adsorbed Water Molecules |
| title_full_unstemmed | First-Principles Study of AlPO4-H3, a Hydrated Aluminophosphate Zeotype Containing Two Different Types of Adsorbed Water Molecules |
| title_short | First-Principles Study of AlPO4-H3, a Hydrated Aluminophosphate Zeotype Containing Two Different Types of Adsorbed Water Molecules |
| title_sort | first principles study of alpo4 h3 a hydrated aluminophosphate zeotype containing two different types of adsorbed water molecules |
| topic | zeolites adsorption density functional theory molecular dynamics crystallography |
| url | http://www.mdpi.com/1420-3049/24/5/922 |
| work_keys_str_mv | AT michaelfischer firstprinciplesstudyofalpo4h3ahydratedaluminophosphatezeotypecontainingtwodifferenttypesofadsorbedwatermolecules |