Functionalized hypercrosslinked organic polymers were prepared by self-condensation of bischloromethyl monomers (DCX or BCMP). Anhydrous FeCl3 (40 mmol) was dissolved in anhydrous DCE (20 mL) and then added into the solution containing 20 mmol monomer and 20 mL DCE under nitrogen atmosphere. The resulting mixture was heated using standard thermal heating and stirred at 80 °C for 24 h. The obtained brown precipitate was separated by filtration, washed three times with methanol, followed with extraction in a Soxhlet extractor with methanol for 24 h and ultimately dried at 100 °C for 12 h (99% yield) . Sulfonation of hypercrosslinked organic polymers was performed by treating with chlorosulfonic RX-3117 in anhydrous DCM. Typically, 1.0 g of the polymer sample was outgassed at 100 °C in a three-necked round flask for 3 h. Then, 20 mL of DCM containing chlorosulfonic acid (4 mL) was slowly added into the flask at 0 °C and the mixture was stirred for 12 h under nitrogen atmosphere. Finally, the acid-functionalized product was obtained by filtration, washing with anhydrous DCM, extraction in a Soxhlet extractor with methanol for 24 h, and drying at 100 °C for 12 h. The C, H, S elemental analysis data for all the hypercrosslinked polymers were listed in Table S1. The deviations between theoretical and experimental values were observed on these polymers due to the incomplete alkylation and trapped adsorbates including catalyst, gases and water vapor within the pores, which are consistent with previous reports ,  and .