A Robust Adenine-Based Microporous Metal-Organic Framework with Hydrophobic Alkyl Groups and Abundant Lewis Basic Sites for CO 2 /N 2 Separation.

The development of a chemically robust metal-organic framework (MOF) with appropriate pore nanospace for efficient CO 2 capture and separation from flue gas under humid conditions is sought after. Herein, an adenine-based microporous MOF, Cu-AD-SA, bearing abundant Lewis basic sites and alkyl groups has been utilized to capture and separate CO 2 from CO 2 /N 2 gas mixtures. The introduction of alkyl groups enable Cu-AD-SA with high chemical stability. The confined pore nanospace involving small pore size and functionalized pore surface decorated by Lewis basic amino and alkyl groups bestows the framework with stronger CO 2 affinity versus N 2 , thus resulting in a high CO 2 /N 2 separation performance even at high operating temperature (323 K) and humidity (80%), as evidenced by breakthrough experiments. Moreover, molecular modeling studies were implemented to establish the adsorption mechanism, in which the ditopic aliphatic carboxylic acids and adenine linkers collaboratively play a vital role in the separation of CO 2 /N 2 gas mixtures via C-H···O CO 2 , C CO 2 ···O, C CO 2 ···N, and C CO 2 ···π interactions.