Amine-Functionalized Triazolate-Based Metal-Organic Frameworks for Enhanced Diluted CO₂ Capture Performance

Efficient CO₂ capture at concentrations between 400-2000 ppm is essential for maintaining air quality in a habitable environment and advancing carbon capture technologies. This study introduces NICS-24 (National Institute of Chemistry Structures No. 24), a Zn-oxalate 3,5-diamino-1,2,4-triazolate framework with two distinct square-shaped channels, designed to enhance CO₂ capture at indoor-relevant concentrations. NICS-24 exhibits a CO₂ uptake of 0.7 mmol/g at 2 mbar and 25 °C, significantly outperforming the compositionally related Zn-oxalate 1,2,4-triazolate - CALF-20 (0.17 mmol/g). Improved performance is attributed to amino-functions that enhance CO₂ binding and enable superior selectivity over N₂ and O₂, achieving 8-fold and 30-fold improvements, respectively, in simulated CO₂/N₂ and CO₂/O₂ atmospheric ratios. In humid environments, NICS-24 retained structural integrity but exhibited an 85 % reduction in CO₂ capacity due to competitive water adsorption. Breakthrough sorption experiments, atomistic NMR analysis, and DFT calculations revealed that water preferentially adsorbs over CO₂ due to strong hydrogen-bonding interactions within the framework. Gained understanding of the interaction between CO₂ and H₂O within the MOF framework could guide the modification via rational design with improved performance under real-world conditions.