Pyrene-Based Porous Organic Polymers as Efficient Catalytic Support for the Synthesis of Biodiesels at Room Temperature

New pyrene-based microporous organic polymers PPOP-1, PPOP-2, and PPOP-3 have been synthesized via Friedel-Crafts alkylation reaction between pyrene and bis(1,4-dibromomethyl)benzene at their different molar ratios in the presence of a Lewis acid catalyst FeCl3 under refluxing conditions. Pore surfaces of PPOP-1, PPOP-2, and PPOP-3 have been functionalized by -SO3H groups via chlorosulfonic acid treatment under controlled reaction conditions to obtain sulfonated porous organic polymers, and these are designated as SPPOP-1, SPPOP-2, and SPPOP-3, respectively. Powder X-ray diffraction, N-2 sorption, HR-TEM, FE-SEM, NH3-TPD, solid state C-13 CP MAS-NMR, and FT-IR spectroscopic tools are employed to characterize these materials. These sulfonated porous polymers showed nanofiber-like or spherical morphology, very high surface acidity, and excellent catalytic activity for the synthesis of biodiesels via esterification/transesterification of long chain fatty acids/esters at room temperature together with very high recycling efficiency, suggesting the future potential of these sulfonated porous polymers in a wide range of sustainable acid-catalyzed chemical reactions.