Synergic morphology engineering and pore functionality within a metal-organic framework for trace CO2 capture

CO2 capture, especially under ultralow-pressure regions (400-10 000 ppm), is extremely essential and challenging to keep the prolonged manual operation in confined spaces and reduce CO2 corrosion in natural gas. Although many MOFs have been covered for CO2 capture, they usually suffered from unheeded morphology engineering associated with diffusion kinetics and unbridgeable CO2 adsorption under ultralow pressure. Herein, we have successfully targeted pyrazine-functionalized Co-MOF (1a') nanocrystals having dapper hexahedral morphology through skillfully integrating morphology engineering and pore functionality. The yielded 1a' paradigm with snug pore microenvironment afforded record-high adsorption performance for trace CO2 capture (1.36 mmol g(-1) at 400 ppm and 5.7 mmol g(-1) at 10 000 ppm), yet eclipsed adsorption behavior for CH4 and N-2 at 298 K. The decent pore geometry awarded 1a' with superior property for CO2/CH4 and CO2/N-2 separation, giving higher IAST selectivity (1454 for 15/85 CO2/N-2 and 494 for 50/50 CO2/CH4). Besides, 1a' showed an improved hydrophobic nature, with a desired CO2/H2O uptake ratio of 0.45 and improved diffusion selectivity (D-M,D-CO2/D-M,D-H2O) of 17.7. Breakthrough tests visualized that 1a' could realize high-purity CO2 (>96%), yielding maximum CO2 productivity (162 and 164.9 litres per kilogram for 18/85 CO2/N-2 and 50/50 CO2/CH4). Modeling simulations have cooperatively revealed the structure-property relationship between guest molecules and the framework. This work presents an advanced benchmark adsorbent for low-concentration CO2 capture from flue gas and natural gas.