Hofmann-type metal-organic frameworks with dual open nickel centers for efficient capture of CO2 from CH4 and N2

The capture of CO2 from flue gas or natural gas plays a significant role in mitigating global warming and improving the energy level of natural gas. However, it is still challenging to design energy-efficient adsorbents that combine high uptake and selectivity. Herein, two Hofmann-type MOFs, Co(Pyz)[Ni(CN)4] and Ni(Pyz) [Ni(CN)4] (termed CoNi-Pyz and NiNi-Pyz), are used to capture and separate CO2. Due to the difference in nodal metals, NiNi-Pyz shows a smaller pore size than CoNi-Pyz. This subtle difference resulted in higher volumetric uptake of CO2 and higher selectivity of CO2/N2 and CO2/CH4. Molecular simulations reveal a closer binding interaction of CO2 with NiNi-Pyz. Finally, the dynamic breakthrough experiment verified that NiNi-Pyz enables the effective separation of binary mixtures of CO2/N2 (v/v = 15/85) and CO2/CH4 (v/v = 50/50).