Multinuclear Magnetic Resonance Spectroscopy Studies of the Structuration of the Tunnels of Sepiolite in the Presence of Intracrystalline Pyridine Molecules
Bibliographic record
Abstract
Sepiolite, a naturally occurring magnesiosilicate nanoporous clay mineral with a tunnel structure, contains two types of water molecules in the structure: zeolitic water trapped inside the tunnels and structural water molecules which interact strongly with magnesium cations. The zeolitic water was removed by heating the sepiolite to 120 degrees C. The partially dehydrated sepiolite absorbed pyridine vapor to produce an intercalated material where the pyridine takes the place of the zeolitic water. 1H solid-state MAS NMR spectroscopy showed that there is isotopic H/D exchange between pyridine-d5 and the remaining structural water molecules of the sepiolite framework. The exchange takes place at room temperature over several days. Wide line solid state 2H NMR of the sequestered pyridine-d5 showed that two populations of pyridine molecules coexist in the material: one very mobile physisorbed population, which can be removed by heating at 90 degrees C, and a population due to pyridine trapped in the tunnels. Except for small in-plane librations, the trapped pyridine was shown to be held rigidly by the sepiolite. When the pyridine intercalated material is heated at 400 degrees C the structural water and some of the pyridine is lost. The remaining pyridine takes the place of the structural water to produce a new inorganic-organic nanohybrid material with the pyridine bound to the terminal Mg(II) in the structure. The pyridine in this material as well as the intercalated material was characterized by slow-spinning 15N and 13C CP/MAS NMR spectroscopy. The 15N NMR was shown to be a very sensitive probe to characterize the various types of pyridine. The data indicate that pyridine molecules in the inorganic-organic nanohybrid material are directly bound to magnesium cations exposed in the tunnels of sepiolite.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".