Highly porous photoluminescent diazaborole-linked polymers: synthesis, characterization, and application to selective gas adsorption

Abstract

The formation of boron–nitrogen (B–N) bonds has been widely explored for the synthesis of small molecules, oligomers, or linear polymers; however, its use in constructing porous organic frameworks remains very scarce. In this study, three highly porous diazaborole-linked polymers (DBLPs) have been synthesized by condensation reactions using 2,3,6,7,14,15-hexaaminotriptycene and aryl boronic acids. DBLPs are microporous and exhibit high Brunauer–Emmett–Teller surface area (730–986 m² g⁻¹) which enable their use in small gas storage and separation. At ambient pressure, the amorphous polymers show high CO₂ (DBLP-4: 4.5 mmol g⁻¹ at 273 K) and H₂ (DBLP-3: 2.13 wt% at 77 K) uptake while their physicochemical nature leads to high CO₂/N₂ (35–42) and moderate CO₂/CH₄ (4.9–6.2) selectivity. The electronic impact of integrating diazaborole moieties into the backbone of these polymers was investigated for DBLP-4 which exhibits green emission with a broad peak ranging from 350 to 680 nm upon excitation with 340 nm in DMF without photobleaching. This study demonstrates the effectiveness of B–N formation in targeting highly porous frameworks with promising optical properties.