Amine-functionalized porous organic polymers for carbon dioxide capture

Abstract

Recent developments in CO₂ capture using porous organic polymers (POPs) have received accrescent attention due to their sorbent properties such as high CO₂ uptake capacity and selectivity, tunable chemical structure and permanent porosity. POPs are constructed using two and/or three-dimensional organic monomers (building blocks) linked to each other through covalent bonding, creating high porosity. The pore structure in POPs is exceptionally stable, which leads to their cyclable CO₂ adsorption performance. However, POPs generally suffer from low CO₂ uptake and selectivity due to their interaction with CO₂ in physisorption limits (20–40 kJ mol⁻¹). Similar to that in other physisorbents, the CO₂ uptake capacity of POPs further decreases under humid conditions. Pursuant to these limitations, amine functionalization in POPs has resulted in enhanced CO₂ uptake performance with improved CO₂ selectivity over non-polar gases such as N₂. More importantly, several types of amine-functionalized POPs showed that the CO₂ uptake could remain intact under humid conditions such as in post-combustion flue gas. This review article covers recent developments in amine-functionalized porous organic polymers. Three main categories of amine functionalization, such as direct amine synthesis, amine impregnation and amine grafting, were investigated in detail by considering the effect of amines on the sorbent properties and CO₂ capture performance of POPs. The recent findings in amine-functionalized POPs were investigated including porous polymeric networks (PPNs), covalent organic frameworks (COFs), amine linked POPs, hyper-crosslinked polymers (HCPs), conjugated microporous polymers (CMPs), benzimidazole linked polymers (BILPs), porous aromatic frameworks (PAFs) and polymers of intrinsic microporosity (PIMs).