Study of the Adsorption of Toluene in Zeolite LiNa−Y by Solid-State NMR Spectroscopy
Bibliographic record
Abstract
The adsorption of toluene inside partially Li + -exchanged zeolite Y (LiNa−Y) was examined by solid-state NMR spectroscopy. The environments of Li + and Na + ions at different sites in the framework before and after adsorption were characterized by 7 Li and 23 Na magic-angle-spinning (MAS) NMR. The information on the dynamic behavior of guest molecules inside the supercage of the zeolite was obtained from wide-line 2 H NMR spectra. The cation−sorbate interactions were directly probed by heteronuclear dipolar coupling based double-resonance experiments such as 7 Li{ 1 H} and 23 Na{ 1 H} rotational-echo double-resonance (REDOR) experiments. Molecular modeling was also performed to assist in interpreting NMR results. The 7 Li and 23 Na MAS results indicate that during ion exchange the incoming Li + ions fill the SI‘ sites first and then the SII sites, and the remaining Na + ions stay mostly at SII sites. The MAS and REDOR results show that the toluene molecules are facially coordinated to the cations at SII sites in the supercage to form a π-complex, resulting in a significant change in chemical shift of the Li + ions and a dramatic reduction in the quadrupolar coupling constant (QCC) of the Na + ions. The 2 H NMR spectra indicate that at room temperature some toluene molecules reorient around the molecular long axis (two-site flip) and others undergo multiple-site jump motion, but at low temperature only two-site flip, at a much slower rate, remains. Both 2 H and REDOR results show that the molecular dynamics of the guest species is also affected by the cation composition.
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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 | 0.000 | 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".