Water‐stable Adenine‐based MOFs with Polar Pores for Selective CO2 Capture

Here, we report two novel water-stable amine-functionalized MOFs, namely IISERP-MOF26 ([NH₂ (CH₃ )₂ ][Cu₂ O(Ad)(BDC)]⋅(H₂ O)₂ (DMA), 1) and IISERP-MOF27 ([NH₂ (CH₃ )₂ ]_1/2 [Zn₄ O(Ad)₃ (BDC)₂ ]⋅(H₂ O)₂ (DMF)_1/2 , 2), which show selective CO₂ capture capabilities. They are made by combining inexpensive and readily available terephthalic acid and N-rich adenine with Cu and Zn, respectively. They possess 1D channels decorated by the free amine group from the adenine and the polarizing oxygen atoms from the terephthalate units. Even more, there are dimethyl ammonium (DMA⁺ ) cations in the pore rendering an electrostatic environment within the channels. The activated Cu- and Zn-MOFs physisorb about 2.7 and 2.2 mmol g^-1 of CO₂ , respectively, with high CO₂ /N₂ and moderate CO₂ /CH₄ selectivity. The calculated heat of adsorption (HOA=21-23 kJ mol^-1 ) for the CO₂ in both MOFs suggest optimal physical interactions which corroborate well with their facile on-off cycling of CO₂ . Notably, both MOFs retain their crystallinity and porosity even after soaking in water for 24 hours as well as upon exposure to steam over 24 hours. The exceptional thermal and chemical stability, favorable CO₂ uptakes and selectivity and low HOA make these MOFs promising sorbents for selective CO₂ capture applications. However, the MOF's low heat of adsorption despite having a highly CO₂ -loving groups lined walls is quite intriguing.