Probing Calcium‐Based Metal‐Organic Frameworks via Natural Abundance <sup>43</sup>Ca Solid‐State NMR Spectroscopy
Bibliographic record
Abstract
Abstract Calcium‐based metal‐organic frameworks (MOFs) are of high importance due to their low cost and bio‐compatible metal centers. Understanding the local environment of calcium in these materials is critical for unraveling the origins of specific MOF properties. 43Ca solid‐state NMR spectroscopy is one of the very few techniques that can directly characterize calcium metal centers, however, the 43Ca nucleus is a very challenging target for solid‐state NMR spectroscopy due to its extremely low natural abundance and resonant frequency. In this work, natural abundance 43Ca solid‐state NMR spectroscopy, at a high magnetic field of 21.1 T, has been employed to characterize several calcium‐based MOFs. We demonstrate that 43Ca NMR spectra and quantum chemical calculations can probe the local structure of calcium metal centers within MOFs, investigate the presence of guests, and monitor phase changes.
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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".