44ª Reunião Anual Virtual da SBQ

Pillar[n]arenes are a class of macrocyclic compounds reported in 2008 by Ogoshi and coworkers, formed by hydroquinone derivatives connected in the 2,5-positions by methylene bridges.1 Due to its high yield synthesis, easy modifications, and electron-rich cavity, these macrocycles are excellent materials for a wide range of applications, such as isomer separation2, gas capture3, drug delivery systems4. Imidazole group is well-known for its interaction with CO2.5 In this scenario we explore the electron-rich cavity combined with an imidazole functionalization for gas adsorption and xylene isomer separation. The P[5]Im in its amorphous form has been synthesized in 3 reactional steps following a procedure previously described in literature.6 The ¹H NMR spectra confirmed the structure of P[5]Im intermediates and the final product (Figure 1a). Single crystals of pure P[5]Im were obtained as transparent needles by slow evaporation of CH3CN:H2O solution in the presence of different cations (Na(I), Ca(II), Sr(II), Ba(II), Mg(II) and Sm(III)) (Figure 1b,c). Although low BET surface area of P[5]Im, 0.062 m2 g-1, (Figure 1d), the material showed a good CO2 adsorption capacity (11 mmol g-1 = 484 mg of CO2/g) at 25°C and high pressure regime (40 bar). The material can also separate xylene isomers.