Hexaazatrinaphthylene-Based Ultrastable Metal–Organic Frameworks Modulated by the Chelating Coordination Configuration for CO₂ Capture

Hexaazatrinaphthylene (HATN), a polyheterocyclic aromatic ligand, is ideal for constructing discrete functional coordination complexes. However, its conjugated rigidity has resulted in a great challenge in forming extended structures with only one 3D metal-organic framework (MOF) reported 24 years ago. Herein, by regulation of the dihedral angle between two chelating HATN planes, three new porous HATN-based MOFs (SNNU-231-233) with mononuclear metal centers were successfully synthesized. SNNU-231, a unique 2-fold interpenetrated MOF, was first assembled, but the interpenetration leads to the lost pores. By modulating coordination configurations, the pore channels were successfully opened in SNNU-232 and SNNU-233, leading to a new topology in SNNU-232 and breaking the interpenetration in SNNU-233. All HATN-based MOFs exhibit exceptional thermal stability above 500 °C, surpassing most reported MOF materials. At the same time, SNNU-233 can keep its structure in water from pH = 1 to 14. Specifically, SNNU-233 had outstanding CO₂ uptake capacity and separation ability of CO₂/N₂ due to its strong affinity to CO₂ molecules in specific pores with abundant hydrogen bonds and π-force adsorption sites. SNNU-233 also showed significant potential for the simulated low calorific value coal gases with five components of H₂ (5.1%), CO (9.1%), CH₄ (5.0%), N₂ (66.3%), and CO₂ (14.3%).