Review on CO₂ Capture Using Amine-Functionalized Materials

Abstract

CO2 capture from industry sectors or directly from the atmosphere is drawing much attention on a global scale because of the drastic changes in the climate and ecosystem which pose a potential threat to human health and life on Earth. In the past decades, CO2 capture technology relied on classical liquid amine scrubbing. Due to its high energy consumption and corrosive property, CO2 capture using solid materials has recently come under the spotlight. A variety of porous solid materials were reported such as zeolites and metal–organic frameworks. However, amine-functionalized porous materials outperform all others in terms of CO2 adsorption capacity and regeneration efficiency. This review provides a brief overview of CO2 capture by various amines and mechanistic aspects for newcomers entering into this field. This review also covers a state-of-the-art regeneration method, visible/UV light-triggered CO2 desorption at room temperature. In the last section, the current issues and future perspectives are summarized.

Fundamental Insight into Humid CO2 Uptake in Direct Air Capture Nanocomposites Using Fluorescence and Portable NMR Relaxometry

“…When we consider both fluorescence and CO 2 sorption data, we observe that the dry samples become glassier much faster, despite having uptaken the same or less CO 2 than the wet samples. The results are fully consistent with the literature, where more humid conditions at low CO 2 concentrations have been mainly reported to promote CO 2 diffusion and to double the CO 2 capacity compared to anhydrous conditions. − We and others hypothesize that the relative formation of bicarbonates and certain carbamate species in the presence of moisture are responsible for different degrees of electrostatic cross-linking in these samples that in turn impact polymer mobility. We probe this hypothesis further in the next two sections by correlating the polymer mobility data inferred by fluorescence with NMR relaxometry data on these same samples.…”

“…The stabilization of these ions over two amines not only keeps the capacity low at 0.5 mol bound CO 2 per mole of amine ,, but also contributes to cross-linking within the polymer or between polymer chains that significantly impedes subsequent CO 2 diffusion. ,, However, unlike in dry conditions, the exact molecular interactions in humid conditions are still debated. Properties such as adsorbent loading, polymer molecular weight, amine functionality, the support, its porosity, and acidity, as well as the RH and CO 2 concentration all have been reported to affect the interaction of PEI with H 2 O and CO 2 . − Despite all these variables, humid conditions at low CO 2 concentrations have been mainly claimed to promote CO 2 diffusion and can even double the CO 2 capacity relative to the anhydrous state. − While the general proposed mechanism in anhydrous conditions involves ammonium carbamate ion formation and cross-linking, when moisture is present, water-stabilized ammonium bicarbonate or hydronium carbamate ions are thought to bind through one ethylamine (Figure a) . Note that ammonium carbamates can be present in both dry and humid conditions; they are also the only species illustrated in Figure a that results in interchain ionic cross-linking.…”

“…In dry conditions, CO 2 reacts with two amines (primary or secondary) to form ammonium carbamate ion pairs (RNH 3 + COO − /R 2 NH 2 + COO − ). The stabilization of these ions over two amines not only keeps the capacity low at 0.5 mol bound CO 2 per mole of amine 59,69,70 but also contributes to cross-linking within the polymer or between polymer chains that significantly impedes subsequent CO 2 diffusion. 38,71,72 However, unlike in dry conditions, the exact molecular interactions in humid conditions are still debated.…”

Direct Air Capture of CO2 Using Amine/Alumina Sorbents at Cold Temperature

“…The ideal CO 2 sorbent should exhibit fast kinetics and high selectivity toward CO 2 from the CO 2 -lean atmosphere (∼420 ppm CO 2 ). Hence, CO 2 should bind strongly to the adsorbent but not so effectively as to require regeneration at temperatures or conditions that will be cost-prohibitive. , Amine-based porous adsorbents have shown potential owing to their high CO 2 uptake capacities and lower temperature requirements for regeneration, which translates to lower energy and hence lower capital requirements. ,,− However, most studies have primarily focused on studying these materials at 25 °C and higher. − Additionally, relatively few studies take into account the effect of water vapor in the atmosphere while evaluating the performance of the sorbents. Temperatures vary significantly across the globe (from −30 to 30 °C), and ∼70% of the world has an average temperature lower than 25 °C. , Studies focusing on cooler conditions (<25 °C) , are few and far between, which precludes informed operation in a large geographical area.…”

An amine decorated MOF for direct capture of CO2 from ambient air

“…51 Other studies also show that the selectivity of MOFs for CO 2 adsorption is improved by the presence of amino groups and exposed metal sites. 47,[52][53][54][55][56][57][58][59][60][61][62][63] Further development and exploration are required to create affordable and uncomplicated CO 2 adsorbents that exhibit both high selectivity and a significant capacity for CO 2 adsorption.…”