Micro–meso–macroporous polymers (MOPs) grafted with versatile functional groups, such as sulfonate, amine, triazole, pyridine, strong acidic ionic liquids and triphenylphosphine, were synthesized by in situ cross-linking of different functional molecules with 1,4-bis(chloromethyl)benzene in the presence of Lewis acid catalysts without using additional templates. The resultant hyper-cross-linked nanoporous polymers show unique characteristics such as large BET surface areas (up to 1523 m² g⁻¹), abundant micro–meso–macropores (4.5–131 nm), and tunable and versatile active sites (acid, base and palladium). These functional polymers exhibit excellent activities and good reusability in biomass conversions, cross-coupling reactions and condensation. The catalytic activities are much better than those of various conventional catalysts such as H₃PW₁₂O₄₀, SBA-15-SO₃H, Amberlyst 15, and mesoporous H-ZSM-5 Pd/C and even as comparable as those of homogeneous H₂SO₄ and HCl in the depolymerization of crystalline cellulose into fine chemicals and towards transesterification to biodiesel. This work highlights a low cost route to the synthesis of solid catalysts based on functional nanoporous polymers for catalyzing the production of clean biofuels and fine chemicals.