Synthesis and structural studies of covalent organic frameworks prepared from polyhedral oligosilsesquioxane for naproxen adsorption
Covalent organic frameworks (COFs) are porous crystalline materials made up of organic components joined by strong reversible covalent bonds that have a persistent influence on the geometry and permeability of the arrangement. These substances are totally composed of light components such as H, B...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2022
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/112137/1/FS%202022%2060%20-%20IR%28UPM%29.pdf |
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| Summary: | Covalent organic frameworks (COFs) are porous crystalline materials made up of
organic components joined by strong reversible covalent bonds that have a persistent
influence on the geometry and permeability of the arrangement. These substances are
totally composed of light components such as H, B, C, N, O, and Si. Pharmaceuticals
and personal care products (PPCPs) are an emerging problem as environmental
contaminants. An "emerging toxin" such as naproxen which a nonsteroidal antiinflammatory
drug, is a toxic compound that has conquered or is manufactured in
significant quantities in an ecosystem, causing some persistence and harm to living
species. Hence, the development of polyhedral oligomeric silesquioxane (POSS) COFs
as adsorbents for the removal of naproxen is crucial. POSS octa(phenyl) silesquioxane
(OPS) was nitrated to produce octa(nitrophenyl) silesquioxane, which was then reduced
to yield octa(aminophenyl)silesquioxane (OAPS). Four newly POSS COFs with various
linkers, namely, COF-S4, OAPS with 1,5-dihydroxyanthraquionone (1,5-DHAQ, L1);
COF-S7, OAPS with 2-methylanthraquionone (2-MeAQ, L2); COF-S12, OAPS with
Terephthalaldehyde (TPA, L3); COF-S14, OAPS with 1,8-dihydroxyanthraquionone
(1,8-DHAQ. L4) were successfully synthesised by solvothermal condensation method
using Schiff base reaction (R₁R₂C=NR'), with a molar ratio 1:8 for OAPS to linker (L1,
L2, L3 and L4), at temperature 120, 125, 100 and 120°C for COF-S4, COF-S7, COF-S12
and COF-S14 respectively. The nanomaterials obtained were investigated using
numerous spectroscopy techniques. The formation of large crystal lattice unit cells of the
COFs frameworks was indicated by the peaks observed at low angles of less than 10°.
The functional groups were investigated by FTIR which exhibited that the formation of
the frameworks was attained through the Schiff base formation (C=N). Similarly, the
Si−O−Si bonds for the synthesised COFs were all shown, which further proved that the
materials were formed. 13C and 28Si CP-MAS NMR analysis confirmed the formation of
the COFs through the C=O peaks in the range 180-200 ppm for the linkers and the
existence of the C=N peaks in the range of 160-180 ppm for the nanomaterials produced.
28Si NMR further affirmed the retention of silicone in the compounds after the synthesis.
The COFs displayed excellent thermal durability for up to 400°C for COF-S4 and COF
S14, and 600°C for COF-S7 and COF-S12, respectively. The structural morphology
FESEM of the compounds obtained displayed that the materials were nano crystals with
nano-grain size pores and demonstrated the presence of all the expected elemental
composition via EDX analysis. N2 physisorption (BET) analysis demonstrated that the
materials showed Type IV isotherm, and H3 hysteresis loop, which is a characteristic of
mesoporous material. The remedied effluent was investigated, and a significant
performance was recorded in the removal capability of the naproxen over COF-S4, COFS7,
COF-S12, and COF-S14 as 76%, 70%, 86% and 77% at a contact time of 210, 210,
270, and 270 min, respectively, at a constant dose of 0.05 g and pH 7. The maximum
adsorption capabilities of the compounds were found to be 37, 35, 42, and 38 mg/g. The
pH effect signifies that there is steady exclusion with a rise in pH to 9. At pH 9, the drop
value was achieved for all COFs except for COF-S12 which was observed at pH 11,
owing to the further negative charge, consequential to the repulsion between the
synthesised COFs and naproxen solution. Investigation of the as-synthesised materials
demonstrated admirable performance in reusability in the adsorption removal of
naproxen. The as-synthesised COFs are envisioned as future adsorbents for removing
anti-inflammatory drugs (AIDs) from water due to their ease of production, notable
adsorption effectiveness, and admirable reusability. |
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