Solid-state CO₂ capture based on the self-assembly of poly(acrylic acid)–N,N′-di-tert-butylethylenediamine (DBEDA) ionic complexes

DBEDA, a sterically hindered secondary diamine, captures CO₂ via a water-mediated bicarbonate pathway rather than carbamate formation. While the crystalline DBEDA monohydrate (DBH) enables crystallization-driven CO₂ capture and release, repeated thermal regeneration causes coarse recrystallization that limits CO₂ diffusion. To overcome this, poly(acrylic acid) (PAA) was incorporated to form a PAA–DBEDA complex with amorphous, ionically confined nanodomains rather than a crystalline hydrate.
 At the optimal PAA:DBEDA ratio of 4 , the complex captures 1.01 mol CO₂ per mol DBEDA, with most uptake completed within 5 min, despite PAA's acidic carboxyl groups, which conventionally suppress amine reactivity. FT-IR/Raman confirm bicarbonate (not carbamate) formation, and the complex retains nearly 95% of its capacity over 10 cycles. The ionic interaction between PAA and DBEDA within confined nanodomains enables fast, reversible, low-energy CO₂ capture, offering a design strategy for reusable solid sorbents.