Imine-linked porous aromatic frameworks based on spirobifluorene building blocks for CO2 separation

Abstract

Porous organic frameworks entirely composed of organic building blocks are attracting more and more attention owing to their tunable porosity, lightweight and hydrolytic stability. Three novel porous aromatic frameworks (PAFs) based on the [4 + 3] design strategy have been synthesized from spirobifluorene building block as square node and various triangle nodes respectively via imine condensation. These materials are all semiconductors and permanently microporous amorphous polymer with high thermal stabilities. The Brunauer-Emmett-Teller (BET) surface areas of these PAFs are between 389 and 698 m 2 /g. More importantly, these frameworks exhibit good CO 2 uptake (4.0 mmol/g for PAF-131) and outstanding ideal adsorption selectivities for CO 2 /N 2 (121 for PAF-131) and CO 2 /CH 4 (327 for PAF-131) at 273 K and 1 bar, thus showing that they are good candidates for CO 2 capture. • Spirobifluorene-based porous aromatic frameworks formed by imine condensation. • Frameworks constructed from [4 + 3] networks of square and triangle nodes. • Materials with semiconductive character and permanently microporosity. • High CO 2 uptake and outstanding adsorption selectivities for CO 2 /N 2 and CO 2 /CH 4 .