Multifunctional Charge and Hydrogen-Bond Effects of Second-Sphere Imidazolium Pendants Promote Capture and Electrochemical Reduction of CO2 in Water Catalyzed by Iron Porphyrins
Bibliographic record
Abstract
Microenvironments tailored by multifunctional secondary coordination sphere groups can enhance catalytic performance at primary metal active sites in natural systems. Here, we capture this biological concept in synthetic systems by developing a family of iron porphyrins decorated imidazolium (im) pendants for the electrochemical CO2 reduction reaction (CO2RR), which promotes multiple synergistic effects to enhance CO2RR and enables the disentangling of second-sphere contributions that stem from each type of interaction. Fe-ortho-im(H), which poises imidazolium units featuring both positive charge and hydrogen-bond capabilities proximal to the active iron center, increases CO2 binding affinity by 25-fold and CO2RR activity by 2,000-fold relative to the parent Fe tetraphenylporphyrin (Fe-TPP), achieving turnover frequencies (TOF) exceeding 109 s-1 with >95% Faradaic efficiency for CO product. Owing to these dual, synergistic second-sphere enhancements, this catalyst also retains high activity and selectivity for homogeneous CO2RR in aqueous media. Notably, the observed TOF value for Fe-ortho-im(H) is 14,000-fold higher than the Fe-para-im(H) positional analog, but only 40-fold higher than the Fe-ortho-im(Me) congener that retains the proximal positive charge but lacks the C2-H hydrogen-bonding moiety, revealing that through-space charge effects have a greater impact on catalytic CO2RR performance compared to hydrogen bonding in this context. This work emphasizes the use of second-sphere pendants that can promote multiple synergistic effects as a design strategy for achieving CO2 reduction catalysis in water.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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 | 0.001 |
| 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 teacher head, 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".