Efficient CH/CO Separation in Ultramicroporous Metal-Organic Frameworks with Record CH Storage Density.

Physical separation of CH from CO on metal-organic frameworks (MOFs) has received substantial research interest due to the advantages of simplicity, security, and energy efficiency. However, that CH and CO exhibit very close physical properties makes their separation exceptionally challenging. Previous work appeared to mostly focused on introducing open metal sites that aims to enhance the CH affinity at desired sites, whereas the reticular manipulation of organic components has rarely been investigated. In this work, by reticulating preselected amino and hydroxy functionalities into isostructural ultramicroporous chiral MOFs-Ni(l-asp)(bpy) () and Ni(l-mal)(bpy) ()-we targeted efficient CH uptake and CH/CO separation, which outperforms most benchmark materials. Explicitly, adsorbs substantial amount of CH with record storage density of 0.81 g mL at ambient conditions, which even exceeds the solid density of CH at 189 K. In addition, gave IAST selectivity of 25 toward equimolar mixture of CH/CO, which is nearly twice higher than that of . Notably, the adsorption enthalpies for CH at zero converge in both MOFs are remarkably low (17.5 kJ mol for and 16.7 kJ mol for ), which to our knowledge are the lowest among efficient rigid CH sorbents. The efficiencies of both MOFs for the separation of CH/CO are validated by multicycle breakthrough experiments. DFT calculations provide molecular-level insight over the adsorption/separation mechanism. Moreover, can survive in boiling water for at least 1 week and can be easily scaled up to kilograms eco-friendly and economically, which is very crucial for potential industrial implementation.