Bis(benzene) and Bis(cyclopentadienyl) V and Cr Doped Mesoporous Silica with High Enthalpies of Hydrogen Adsorption
Bibliographic record
Abstract
Hexagonally packed mesoporous silica synthesized using a dodecylamine template was treated with bis(cyclopentadienyl) chromium, bis(cyclopentadienyl) vanadium, and bis(benzene) vanadium. The obtained composite samples were characterized by nitrogen adsorption, X-ray powder diffraction, and X-ray photoelectron spectroscopy. These materials were then studied for hydrogen adsorption and storage capacities to determine the effect of metal doping and the degree of Kubas binding to the metals in these systems. By studying the hydrogen adsorption at two temperatures of 77 and 87 K, the heats of adsorption were also obtained by fitting the data in Clapeyron−Clausius equation. The composite samples all possess higher adsorption and storage capacities than pristine silica, and all show the same rising trend of adsorption enthalpies as a function of surface coverage observed in previous studies from our group on mesoporous oxides with reduced transition metal centers on the surface. The highest enthalpy recorded was 18.43 kJ mol H 2 −1 in the case of bis(cyclopentadienyl) chromium treated silica, which is the second highest enthalpy of hydrogen binding ever reported for a porous material behind benzyltitanium grafted silicas also studied by our group, which show enthalpies of 23 kJ mol H 2 −1 . Unlike these benzyltitaium materials, which decompose over several weeks in an inert atmosphere at room temperature to gradually lose their adsorption capacity, this Cr-grafted sample retains its adsorption capacity after 3 months in inert atmosphere. As suggested by the higher enthalpies of adsorption, substantial degrees of performance of the chromium metal centers were retained at −78 °C (71%) and room temperature (RT) (18%) in comparison with the performance of this sample at 77 K.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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".