Probing the Morphology and Mobility of Amines in Porous Silica CO₂ Sorbents by ¹H <i>T</i>₁–<i>T</i>₂ Relaxation Correlation NMR

Molecular and oligomeric amines supported in porous oxide supports are a promising class of CO2 sorbent materials studied for removal from diverse streams such as flue gas ambient air. Among the various investigated, low molecular weight, hyperbranched poly(ethyleneimine) (PEI), tetraethylenepentamine (TEPA) among most extensively studied. While macroscopic structure–performance relationships relating support structure, amine loading, other factors affecting sorption capacities kinetics have been developed, structural dynamic information about organic phase is less plentiful. The structure mobility impregnated pores directly impact sorption, accessibility sites relates to distribution overall pore filling well dynamics chains. Here, we prepare family mesoporous silica SBA-15 containing varying loadings (PEI) amines. 1H T1–T2 relaxation correlation solid-state NMR experiments used characterize properties confined Both TEPA PEI shown form multiple different domains pores, each with distinguishable properties. more rigid layers around walls at lower loading fractions, characterized by mobilities, followed formation mobile engaged wall interactions higher loadings. shows faster mobilities than because its weight. also appears easily transfer between within leading generally uptake rates capacities, while located closer remained much thus capture.