The adsorption and desorption mechanisms of CO2 in hyperbranched amine-functionalized sisal fiber adsorbents were systematically investigated to understand the interplay between chemical reactivity, physical structure, and thermo-responsive behavior. The material SF-AM-co-NIPAM-HBP-NH2 (1:1) exhibits a dual-mode mechanism for CO2 capture: a primary chemisorption pathway via formation of carbamate and bicarbonate species with primary and secondary amines, and a secondary physical adsorption component driven by capillary forces within the porous network created by grafting.
FTIR and 13C NMR analyses confirmed the presence of abundant –NH2 and –NH groups after hyperbranched amination, which readily react with CO2 in both dry and humid conditions. In the presence of moisture, the reaction proceeds through a well-established pathway involving proton transfer and carbonate formation, allowing the adsorption capacity to exceed the theoretical 0.5 mol CO2/mol amine limit. This enhancement is attributed to the stabilization of intermediates by water molecules and the high density of accessible amine sites enabled by the branched architecture.
The desorption process is governed by the thermally induced phase transition of PNIPAM chains. Below the LCST (~50–60 °C), the polymer remains hydrated and extended, maintaining strong hydrogen bonding with adsorbed CO2 species. Upon heating above the LCST, the PNIPAM segments undergo intramolecular hydrogen bonding, leading to chain collapse and dehydration. This structural change reduces the interaction strength between the amine groups and CO2 adducts, facilitating the release of CO2 under mild thermal conditions without requiring high-energy input.
Kinetic modeling using pseudo-first-order, pseudo-second-order, and Avrami equations revealed that the adsorption process is best described by the Avrami model, indicating a combination of diffusion-controlled mass transfer and nucleation-growth phenomena. The rate-limiting step involves both the penetration of CO2 into the swollen polymer matrix and the subsequent chemical reaction with active amine sites. The regeneration kinetics further confirm that desorption is rapid and complete at 60 °C, consistent with the sharp swelling ratio drop observed in the transition region.80451-05-4 Synonym
SEM and TGA data support this mechanistic picture, showing intact fiber morphology after multiple cycles and no significant weight loss below 200 °C, indicating minimal degradation.172889-27-9 Biological Activity These findings collectively demonstrate that the synergy between hyperbranched amine functionality and thermoresponsive polymer grafting enables efficient, reversible, and energy-saving CO2 capture.PMID:30726029 The proposed mechanism not only explains the superior performance of this material but also provides a design blueprint for future smart sorbents combining tailored chemistry with dynamic environmental responsiveness.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com