A permanently porous single molecule H-bonded organic framework for selective CO2 capture

Abstract

Permanent porosity has been realized in a hydrogen bonded framework formed by a single tripodal tricarboxylic acid molecule. The presence of three phenyl rings linked to a flexible sp³ nitrogen centre renders a near-propeller shape to the molecule generating an unusual ‘non-planar’ 3-D framework formed by highly directional planar –COOH⋯HOOC– hydrogen bonds, propagating in all three directions. The material shows exceptional hydrolytic, acidic and thermal stability and has a surface area of 1025 m² g⁻¹. Importantly, it shows preferential adsorption of CO₂ over N₂ with very high selectivities (350 : 1@1 bar, 303 K). DFT modeling shows the presence of stable T-shaped CO₂⋯CO₂ dimers within the channels suggesting favorable co-operativity between them.