Two open metal sites on the same metal: Dynamics of CO2 in MOF UTSA-74
Bibliographic record
Abstract
Metal-organic frameworks (MOFs) are an emerging class of porous materials with many unique properties that make them promising candidates for carbon dioxide (CO 2 ) capture and storage. A better understanding of the behavior of CO 2 adsorbed inside MOF will enable researchers to develop the ability of designing new MOF based materials with high CO 2 adsorption capabilities. It is well known that presence of open metal sites (OMSs) can greatly enhance the gas adsorption capability of MOFs. MOF UTSA-74, a framework isomer of well-known MOF-74 has a unique feature that upon activation, a single metal ion has two OMSs. Therefore, it presents a unique opportunity to probe the dynamics of CO 2 molecules adsorbed on these OMSs. In this work, the CO 2 adsorptive properties of MOF UTSA-74 are examined with particular attention being paid to the dynamics of the CO 2 adsorbed on these OMSs. Specifically, variable temperature 13 C static solid-state nuclear magnetic resonance (SSNMR) experiments were conducted to directly monitor the behavior of 13 CO 2 in UTSA-74 at different loadings. All CO 2 molecules undergo localized wobbling. At low loadings, some CO 2 molecules jump among three OMSs from three different Zn atoms in the cross-section of the channel. Others hop back and forth between the two neighboring OMSs. At high loading, the three-site jump has ceased, but two-site hopping persists. The dynamical behavior of CO 2 in UTSA-74 results from the unique Zn coordination environment. It was discovered that CO 2 is less mobile in UTSA-74 than in its framework isomer, MOF-74-Zn.
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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 | 0.001 |
| 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".