Porous organic polymers derived from tetrahedral silicon-centered monomers and a stereocontorted spirobifluorene-based precursor: synthesis, porosity and carbon dioxide sorption

Abstract

Sonogashira–Hagihara coupling reactions of tetrahedral silicon-centered monomers, i.e., tetrakis(4-bromophenyl)silane (p-Si) and tetrakis(3-bromophenyl)silane (m-Si), and stereocontorted 2,2′,7,7′-tetraethynyl-9,9′-spirobifluorene (TESF) result in two novel porous organic polymers, POP-1 and POP-2. Compared with other porous polymers, these materials show high thermal stability and comparable specific surface areas with Brunauer–Emmer–Teller surface areas of up to 983 m² g⁻¹, and total pore volumes of up to 0.81 cm³ g⁻¹ (POP-1). The N₂ isotherm analysis reveals that their porosities could be tuned by changing the structure geometry of the silicon-centered monomers. Further porosity comparison with other porous polymers indicates that the introduction of silicon-centered units in the porous networks could increase the porosity and copolymerization, i.e., changing the second monomer, is an efficient strategy to tune the porosity of the final materials. For applications, the resulting materials show moderate carbon dioxide uptakes of up to 1.92 mmol g⁻¹ (8.45 wt%) at 273 K and 1.03 bar, and 1.12 mmol g⁻¹ (4.93 wt%) at 298 K and 1.01 bar (POP-1), and also a comparably high binding ability with CO₂ with an isostreic heat of 26.8 kJ mol⁻¹ (POP-1). Moreover, the materials exhibited moderate selectivity of CO₂ over other gases, including N₂, O₂ and CH₄. These results reveal that these materials could be potentially applied as promising candidates for storing and capturing CO₂.