Highly controllable CO2 capture performance under varied humidity conditions by finely tuned metal and organic ligand compositions of DMOF adsorbents

Excessive CO 2 emissions significantly contribute to global warming, promoting the advancement of carbon capture and storage (CCS) technologies. Metal-organic frameworks (MOFs) are promising candidates for selective CO 2 adsorption; however, their effectiveness is often compromised in humid environments, such as flue gas streams. To overcome this limitation, this study synthesizes six isostructural DABCO-pillared MOFs (DMOFs) by finely tuning metal nodes (from Zn to Ni) and integrating methyl (-CH 3 ) functional groups on the organic ligand to enhance CO 2 adsorption performance, especially under humid conditions. Single gas adsorption isotherms reveal that the Ni-TM DMOF achieves the highest CO 2 adsorption capacity of 5.0 mmol g −1 and maintains 100 % regenerability after five cycles. Binary CO 2 /N 2 dynamic breakthrough experiments further demonstrate that the Ni-TM DMOF excels in both CO 2 uptake and CO 2 /N 2 separation performance under both dry and humid conditions (80 % relative humidity). Mechanistic insights from in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT) calculations elucidate the molecular interactions between CO 2 and the DMOF structure, revealing that CO 2 adsorption predominantly occurs via physisorption, enhanced by C-H·O interaction from the -CH 3 groups. This work provides a strategic approach for enhancing the stability and efficiency of MOFs in industrial CO 2 sequestration applications.