Poly(glycidyl amine)-Loaded SBA-15 Sorbents for CO₂ Capture from Dilute and Ultradilute Gas Mixtures

Solid-supported amine-based polymers are known to be effective for CO2 capture from dilute streams, including flue gas and ambient air. In this work, we report the synthesis of well-defined poly(glycidyl amine) (PGA) prepared via controlled anionic polymerization followed by postpolymerization modifications and demonstrate the use of PGA-loaded mesoporous silica (SBA-15) for CO2 capture from dilute streams (flue gas) as well as from ultradilute streams (direct air capture). A series of PGA materials with varied molecular weight (χn = 15, 25, and 50) is synthesized via anionic ring-opening polymerization (ROP) and subsequent postpolymerization modifications. The resulting polymers are obtained with relatively narrow polydispersity and predetermined molecular weights. PGA is impregnated into mesoporous silica SBA-15 at different amine loadings (3–8 mmol of N/g of SiO2) and characterized by thermogravimetric analysis (TGA) and N2 physisorption techniques. The performance of the PGA/SBA-15 composites is investigated over a range of CO2 partial pressures and adsorption temperatures and compared to a benchmark material, branched poly(ethylenimine) (PEI)/SBA-15. PGA shows trends in its CO2 capture performance that are different from PEI sorbents but similar to sorbents based on poly(allylamine) (PAA), an oxygen-free analogue to PGA. The effect of oxidative treatment under simulated air (21% O2) for 24 h at 110 °C on the CO2 uptake performance is also evaluated, and PGA is shown to degrade less than PEI on a relative basis. Single-component water vapor sorption isotherms of PGA-loaded SBA-15 are generated at 35 °C and compared against branched PEI-loaded SBA-15 to assess material hydrophobicity. PGA is demonstrated to be a candidate polymer in amine/oxide hybrid CO2 sorbents.