Metamorphosis of Ordered Mesopores to Micropores: Periodic Silica with Unprecedented Loading of Pendant Reactive Organic Groups Transforms to Periodic Microporous Silica with Tailorable Pore Size
Bibliographic record
Abstract
Ordered porous silicas with unprecedented loadings of pendant vinyl groups have been synthesized via co-condensation of tetraethyl orthosilicate (TEOS) and triethoxyvinylsilane (TEVS) under basic conditions in the presence of cetyltrimethylammonium surfactant. The resulting organosilicate-surfactant composites exhibited at least one low-angle X-ray diffraction (XRD) peak up to the TEVS:TEOS molar ratio of 7:3 (70% TEVS loading) in the synthesis gel. The surfactant was removed from these composites without any structural collapse. Nitrogen adsorption provided strong evidence of the presence of uniformly sized pores and the lack of phase separation up to TEVS:TEOS ratios as high as 13:7 (65% TEVS loading), whereas (29)Si MAS NMR and high-resolution thermogravimetry showed essentially quantitative incorporation of the organosilane. Thus, a hitherto unachieved loading level for pendant groups, considered by many to be impossible to achieve for stable organosilicas because of the expected framework connectivity constraints, has been obtained. The resulting vinyl-functionalized silicas exhibited gradually decreasing pore diameter (from 2.8 to 1.7 nm for TEVS loadings of 25-65%) and pore volume as the loading of pendant groups increased, but the specific surface area was relatively constant. Because of the reactivity of vinyl groups, ordered silicas with very high loadings of these groups are expected to be robust starting materials for the synthesis of other organic-functionalized ordered microporous materials. Herein, we demonstrate that these starting materials can also be transformed via calcination into ordered microporous silicas with pore diameters tailorable from 2.5 to as little as 1.4 nm simply by using an appropriate loading of the vinyl-functionalized precursor. This ease of the micropore size adjustment and the attained degree of structural ordering (as judged from XRD) have not been reported before. The novel ordered microporous materials reported herein are promising as adsorbents and catalyst supports.
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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) | 0.000 | 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".