Fig. 1. (a) General scheme for the syntheses of P1 and P2 polymers incorporating various Brønsted acid groups. P1 polymers were synthesized using a postsynthetic modification strategy starting from PAF-1, while the P2 polymers were prepared through Suzuki coupling polymerization. Conditions: (i) Ni(cod)2, 2,2′-bipyridine, DMF. (ii) Cu(NO3)2, Ac2O, then NaS2O4; HCl, 1,4-dioxane. (iii) ClSO3H, CH2Cl2. (iv) HCHO, HCl, H3PO4, AcOH; P(OEt)3; Me3SiBr, CH2Cl2, then MeOH. (v) SPhos Pd G2, K2CO3, H2O, THF. (vi) HCl, 1,4-dioxane. (vii) NaN3, DMSO, then HCl. (viii) KOH, DMSO. (b) Illustration of non-interpenetrated (P1) and interpenetrated (P2) polymer structures to demonstrate the proximity of Brønsted acidic sites in each structure type.
