Site-Dependent Substitutions in Mixed-Metal Metal–Organic Frameworks: A Case Study and Guidelines for Analogous Systems
Bibliographic record
Abstract
Complex architectures are often found among metal–organic framework (MOF) compounds. The mixed-metal approach to this type of material offers an additional degree of structural complexity, and potential tunability of their properties, which remains largely unexplored. We present an in-depth investigation of the crystal chemistry of mixed-metal MOFs based on succinate linkers (C 4 H 4 O 4 ) and having the general formula (M′ 1– x M″ x ) 5 (OH) 2 (C 4 H 4 O 4 ) 4 with M′/M″ = Mn/Co, Fe/Co, and Mn/Fe. The distribution of the metallic elements over three crystallographic sites throughout the different substitutions is finely characterized by resonant contrast diffraction (RCD) experiments corroborated by neutron diffraction (ND) measurements. We observe a size-effect in the filling of the oxygen octahedra, leading to the existence of compounds in which a partial order of the cations over the different metallic sites exists for some compositions of the Co/Mn solid solution. This points out the existence of complex structural phenomena potentially able to influence the physical behavior of such phases and that might, so far, have been overlooked in MOFs. In order to facilitate future studies on mixed-metal MOFs, we consider the possibility of using conventional single-crystal X-ray diffraction (SCXRD) to locate cations of close electronic densities in such cases. The comparison with the results from dedicated measurements based on synchrotron (RCD) and neutron (ND) radiations indicates guidelines for the use of laboratory SCXRD to address mixed-metal MOFs where metal distribution is fundamental to tuning physical properties.
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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 | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 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".