Metal–Organic Frameworks for Capturing Dissolved Carbon Dioxide and Generated Carbonate Ions from Water
Subhajit Dutta, Jacopo Andreo, Nagore Barroso, Aleksander Ejsmont, Bettina Baumgartner, Agata Jankowska, Jonas Tittel, Zeynep Pinar Haslak, Hakan Demir, Ilknur Erucar, Rafael Marcé, Marcin Frankowski, Bert M. Weckhuysen, Evelyn Ploetz, Joanna Goscianska, Stefan WuttkeAbstract
Anthropogenic CO2 emissions are the major driver of climate change of this century. The natural hydrological cycles cause atmospheric CO2 to be absorbed by the natural water bodies, which necessitates urgent removal of dissolved CO2 and its generated carbonate species from water. Here, we present a pH-resolved benchmark that maps how switching from gas-phase CO2 to aqueous inorganic carbon (CO2(aq)/HCO3–/CO32–) changes the governing host–guest interactions in MOFs. By comparing seven archetypal MOFs spanning open metal sites, linker basicity, framework flexibility, and size-selective apertures, we identify three actionable adsorption regimes: (i) metal-site dominated uptake under acidic CO2(aq) conditions, (ii) flexibility-assisted uptake at intermediate pH, and (iii) basic-pore/ion-pairing dominated uptake under alkaline bicarbonate/carbonate conditions. Single-component adsorption studies revealed remarkably diverse CO2 removal performances, highlighting the key roles of the pH (e.g., 2, 6.3, 8.3, and 10) and the nature of the carbonic species present. Among all materials, JUK-8 exhibited the highest adsorption capacity of 6.79 mmol/g toward carbonic acid species at pH 6.3 (CO2 and HCO3¯). Importantly, the MOFs also exhibited substantial removal performance when tested in diverse natural water samples.