Crystal Engineering in the Service of Carbon Capture: From Rapid Synthesis to Operation under Humid Conditions

Industrial-scale carbon dioxide (CO 2 ) capture is essential for achieving global net-zero emission targets. Achieving this at scale demands the development of materials that exhibit high CO 2 uptake, fast kinetics, humidity tolerance, ease of regeneration, thermal stability, and suitability for streamlined production processes. Here, we report the synthesis and characterization of CALF-20-AT, a chemically modified metal–organic framework derived from CALF-20 via solvent-assisted ligand exchange with 3-amino-1,2,4-triazole (AT). This mild postsynthetic modification enhances CALF-20-AT’s CO 2 uptake and binding affinity compared to CALF-20. CALF-20-AT achieves a CO 2 uptake of 2.33 mmol/g from a gas stream containing 4% CO 2 at ambient conditions within 2 min, outperforming CALF-20. Notably, the material maintains ∼85% of its uptake capacity under 70% relative humidity, can be fully regenerated at 60 °C in under 3 min, and demonstrates exceptional stability over 100 adsorption–desorption (dry and humid) cycles. Breakthrough experiments confirm preferential CO 2 adsorption under humid conditions and full recovery after saturation with water vapor. CALF-20-AT’s simple synthesis, use of low-cost precursors, rapid adsorption kinetics, and humidity tolerance make it a strong candidate for natural gas flue gas capture technologies. These properties also provide a valuable blueprint for the rational design of future MOFs optimized for realistic operating environments.