New Frontiers of Triazolate-based MOFs: Amine-Functionalization for Enhanced Diluted CO2 Capture Performance

Capturing CO2 at low concentrations is essential for mitigating indoor air pollution and meeting the increasing demand for effective carbon capture technologies in environments where even trace levels of CO2 can significantly impact human health. This study introduces preparation of novel Zn(II)-based metal-organic framework, NICS-24, featuring diaminotriazole and oxalate linkers which form two types of square-shaped channels. NICS-24 was compared with compositionally related triazolate oxalate (CALF-20) and aminotriazolate oxalate (CALF-15) materials to evaluate the impact of amino functions on CO2 capture capabilities. While CALF-20 showed the highest CO2 uptake at 1 bar, NICS-24 excelled in capturing CO2 at low partial pressures, achieving 1.2 mmol/g at 2 mbar. The presence of amine functions in NICS-24 significantly enhanced CO2 binding and improved selectivity over N2 and O2, driven by narrower pores in comparison to CALF-20. In humid environment, NICS-24 maintained its structural integrity but exhibited reduced CO2 capture performance. In-depth investigation into CO2 adsorption mechanism under humid conditions was conducted, through the aspects of sorption breakthrough experiments, atomistic NMR studies and DFT computational approach. Competitive adsorption mechanism is in favour to water due to the specific framework hydrogen-bonding interactions. Gained understanding of the interaction between CO2 and water within the MOF framework could guide the modification via rational design with improved performance under real-world condition.