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

The development of a chemically robust metal-organic framework (MOF) with appropriate pore nanospace for efficient CO 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 from CO/N 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 affinity versus N, thus resulting in a high CO/N 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/N gas mixtures via C-H···O, C···O, C···N, and C···π interactions.