CO2 capture from wet flue gas using transition metal inserted porphyrin-based metal-organic frameworks as efficient adsorbents

CO 2 capture from large point sources is indispensable for achieving 1.5 degree target as long as fossil fuels are still in use. Selective adsorption of CO 2 from flue gas constitutes a promising CO 2 capture technology, thanks to the development of numerous fascinating solid adsorbents in the past three decades. However, very few adsorbents can retain their required performance in the presence of moisture which is unfortunately always the case in reality. In this study, we elevated the CO 2 adsorption and separation performance of a water-stable aluminum-based porphyrin metal-organic frameworks (Al-PMOF) by inserting transition metals as adsorption sites. Compared with the pristine Al-PMOF and other four transition metals (TMs) incorporated PMOFs (Al-PMOF(M)), the Co-inserted Al-PMOF (Al-PMOF(Co)) exhibited the highest CO 2 adsorption capacity (3.32 mmol/g) and highest CO 2 /N 2 and CO 2 /CH 4 selectivity (87 and 20, respectively) at 273 K and 1.0 bar. After three consecutive cyclic moisture treatments, the CO 2 adsorption capacity of Al-PMOF(Co) remained almost unchanged. More importantly, the dynamic binary CO 2 /N 2 breakthrough adsorption of Al-PMOF(Co) exhibited negligible differences in CO 2 adsorption capacities between dry and wet flue gas conditions, suggesting that TMs incorporated Al-PMOF possess excellent moisture-resistant properties. Mechanistic studies using the combined in situ synchrotron infrared spectroscopic and powder X-ray diffraction together with density functional theory calculations unambiguously revealed the inserted metals are the dominant CO 2 adsorption sites. This study materializes the rational design of efficient adsorbents for CO 2 capture and contributes to mitigating climate change.