A Solid-State NMR Spectroscopic Study of the Adsorption of Toluene in Zeolite LiK-L
Bibliographic record
Abstract
The adsorption of toluene in partially Li + -exchanged zeolite K-L (LiK-L) was examined by solid-state NMR spectroscopy. The environment of the Li + ions at different sites in the zeolite before and after adsorption was characterized by 7 Li magic-angle spinning (MAS) NMR. 1 H → 7 Li cross polarization (CP) and 7 Li{ 1 H} rotational-echo double-resonance (REDOR) experiments were performed to probe the cation−sorbate interactions. The data were also used for spectral assignment. The 7 Li NMR results indicate that most of the Li + ions occupy the sites A (39%) and B (43%) and that there are fewer Li + ions at sites C (17%) and D (1%). The four 7 Li NMR signals corresponding to the Li + ions at four sites are not resolved in the spectrum of the dehydrated zeolite, but are well-separated after the adsorption of toluene. The NMR results show that a toluene molecule is directly coordinated to the Li + ion at site D near the wall of the main channel via formation of a π-complex, resulting in a significant change in 7 Li chemical shift toward a more shielded direction. Although not directly accessible by the toluene molecules, the Li + ions at sites A and C also exhibit an observable shift upon adsorption. Only the Li + ions at site B do not experience a significant change in chemical shift. The effect of the adsorption on 7 Li chemical shift is discussed. Dynamic behavior of toluene molecules inside the channels was also investigated by wide-line 2 H NMR.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".