Click chemistry-derived Polymers of Intrinsic Microporosity (PIMs) with CO2-philic tetrazole groups: chemistry and gas transport
Bibliographic record
Abstract
The well-known spirocyclic ladder polymer of intrinsic microporosity (PIM-1) [1] was modified using a “click chemistry” [2 + 3] cycloaddition reaction to yield novel PIMs containing tetrazole units. The complete conversion of the nitrile to tetrazole groups on PIM-1 with sodium azide and zinc chloride was achieved without chain degradation. As far as we are aware, this is the first report of the conversion of a polymeric aromatic nitrile to tetrazole. The resulting tetrazole-substituted PIM (TZ-PIM) was characterized by Fourier transform infrared spectroscopy (FTIR), and proton nuclear magnetic resonance (1H NMR spectra), and a methyl-TZ-PIM derivative allowed further elucidation by gel permeation chromatography (GPC), and other methods. A series of TZ-PIMs containing various amounts of tetrazole substituents had distinctly better solubility in protic solvents (such as DMF, DMSO, DMAc) compared with the nitrile-containing PIM-1 precursor. The TZ-PIM series were evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), which showed that the polymeric tetrazoles had an onset of decomposition at ~190 °C. Compared with PIM-1, the TZ-PIM series showed higher selectivity for pure gas pairs, such as CO2/N2 and for mixed CO2/N2, with a corresponding decrease in permeability. Good selectivity coupled with high permeability combines to exceed the Robeson upper-bound (2008) performance limit for pure gas pairs CO2/N2 . Additionally, the CO2/N2 mixed gas with different feed compositions surprisingly shows even higher selectivity with moderate permeability, exceeding the Robeson upper-bound (2008) by a greater extent. This could be rationalized by preferential selective sorption of CO2 in TZ-PIM, enhanced by strong interaction with tetrazole, thereby hindering the transport of N2 in gas mixtures [2]. This work extends the spectrum of PIMs beyond those reported previously and also demonstrates that significant improvements in gas transport properties may be achieved through post-modification of PIM materials containing nitrile groups.
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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) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.002 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.115 | 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".