Grand-Canonical Monte Carlo and Molecular-Dynamics Simulations of Carbon-Dioxide and Carbon-Monoxide Adsorption in Zeolitic Imidazolate Framework Materials
Bibliographic record
Abstract
The nature of guest binding sites and selectivity in the zeolitic imidazolate framework (ZIF) 68 and 69 structures are studied by grand-canonical Monte Carlo and molecular-dynamics simulations. We have used the force field of Liu and co-workers to simulate CO 2 and CO adsorption isotherms in the ZIF 68 and 69 structures at 273 K for pressures up to 1 atm. The experimental CO 2 adsorption isotherms are reproduced with good accuracy, but the same force-field protocol overestimates the CO adsorption isotherms. In addition to the total guest adsorption in the unit cell of the ZIF structures from the adsorption isotherms, we determined the relative distribution of the guests in the pores and channels. The nature and number of the binding sites in the channels and pores are determined from the guest probability distributions in the ZIF structures. We find that the CO 2 molecules associate strongly with the benzene rings of the benzimidazolate anion. The binding energies in the pores and channels for different numbers of CO 2 and CO guests have been calculated from molecular-dynamics simulations. As expected, the binding energies of the CO guests in the lattice are much smaller than those of CO 2 . We have also studied the diffusion of the CO 2 and CO guests in the pores and channels of the two ZIF structures. The size of the guest and the aperture size in lattice affect the diffusion rates considerably, and the guests do not diffuse through the pores and channels at equal rates.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".