Porous polymers were prepared by cyclotrimerization reaction in molten p-toluenesulfonic acid. Their properties could be tailored by functionalization of the aromatic diacetyl monomers. Thus, a range of homo- and copolymers based on hydrogen-, amine-, or nitro-functionalized 4,4′-diacetylbiphenyl derivatives and 1,4-diacetylbenzene was synthesized. The pores size could be tuned from mainly microporous to hierarchical micro- and mesoporous or even hierarchical micro- and macroporous. BET surface areas up to 720 m²/g and total pore volumes up to 1.76 cm³/g were achieved. The formation of different pore types was related to the solvent-monomer/polymer interactions, which is shown by ¹⁵N solid state MAS NMR spectroscopy and SEM. Other physical properties such as surface polarity and thermal stability were influenced by the different monomers as well.