Covalent Immobilization of Quaternary Ammonium Salts on Covalent Organic Framework: Sustainable Intensification Strategy for the Synthesis of Cyclic Carbonates from CO<sub>2</sub>
Bibliographic record
Abstract
Sustainable metal-free catalytic conversion of carbon dioxide (CO 2 ) via cycloaddition of epoxides with CO 2 has shown great promise but suffers from a lack of recyclability because of the homogeneous nature, limiting their use. Heterogeneous organocatalysts have gained immense attention in the last decade because of superior application potential and their important characteristics, and they also play pivotal roles in making environmentally friendly processes a reality. Herein, we describe an unprecedented postsynthetic modification approach for efficient covalent immobilization of quaternary ammonium salts to a microporous covalent organic framework (COF). More interestingly, no noticeable loss in crystallinity occurred after postsynthetic modification (PSM) and the quaternary ammonium salt-decorated COF (MA-PDA IL@COF) consists of only micropores (around 6–15 Å), which are smaller than most of the reported COF-based catalysts. Detailed investigations on CO 2 chemical fixation reveal that ionic liquid-based COF is a promising metal-free catalyst to promote the coupling of CO 2 with epoxides under very mild conditions (metal-free/solvent-free/cocatalyst-free/additive-free and 1 atm of CO 2 pressure). The metal-free COF displayed quantitative selectivity, and more intriguingly, the cycloaddition reaction with CO 2 occurred with a high efficiency, broad scope, and functional group tolerance without additives or cocatalysts. The catalytic system can be recovered for repeated use at least five times with almost similar catalytic performance and a promising prerequisite for industrial implementation.
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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 | 0.000 |
| 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".