Enhanced Carbon Dioxide Capture from Diluted Streams with Functionalized Metal–Organic Frameworks
Andrzej Gładysiak, Ah‐Young Song, Rebecca Vismara, M. E. Waite, Nawal M. Alghoraibi, Ammar Alahmed, Mourad Younes, Hongliang Huang, Jeffrey A. Reimer, Kyriakos C. Stylianou
Abstract
High Resolution Image Download MS PowerPoint Slide Capturing carbon dioxide from diluted streams, such as flue gas originating from natural gas combustion, can be achieved using recyclable, humidity-resistant porous materials. Three such materials were synthesized by chemically modifying the pores of metal–organic frameworks (MOFs) with Lewis basic functional groups. These materials included aluminum 1,2,4,5-tetrakis(4-carboxylatophenyl) benzene (Al-TCPB) and two novel MOFs: Al-TCPB(OH), and Al-TCPB(NH 2 ), both isostructural to Al-TCPB, and chemically and thermally stable. Single-component adsorption isotherms revealed significantly increased CO 2 uptakes upon pore functionalization. Breakthrough experiments using a 4/96 CO 2 /N 2 gas mixture humidified up to 75% RH at 25 °C showed that Al-TCPB(OH) displayed the highest CO 2 dynamic breakthrough capacity (0.52 mmol/g) followed by that of Al-TCPB(NH 2 ) (0.47 mmol/g) and Al-TCPB (0.26 mmol/g). All three materials demonstrated excellent recyclability over eight humid breakthrough-regeneration cycles. Solid-state nuclear magnetic resonance spectra revealed that upon CO 2 /H 2 O loading, H 2 O molecules do not interfere with CO 2 physisorption and are localized near the Al-O(H) chain and the –NH 2 functional group, whereas CO 2 molecules are spatially confined in Al-TCPB(OH) and relatively mobile in Al-TCPB(NH 2 ). Density functional theory calculations confirmed the impact of the adsorbaphore site between of two parallel ligand-forming benzene rings for CO 2 capture. Our study elucidates how pore functionalization influences the fundamental adsorption properties of MOFs, underscoring their practical potential as porous sorbent materials.