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

Industrial-scale carbon dioxide (CO2) capture is essential for achieving global net-zero emission targets. Achieving this at scale demands the development of materials that exhibit high CO2 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 CO2 uptake and binding affinity compared to CALF-20. CALF-20-AT achieves a CO2 uptake of 2.33 mmol/g from a gas stream containing 4% CO2 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 CO2 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.