The development of sustainable, metal-free photocatalysts that combine homogeneous reactivity with effective recyclability remains a key challenge in photoredox catalysis. Here, we report a series of rationally designed polymers of intrinsic microporosity (PIMs) tailored for visible light-driven photoredox reactions. Using a multidisciplinary approach by integrating in silico predictions, photophysical and materials characterization, and a series of benchmarking studies, we establish these PIMs as highly effective photocatalysts with broad applicability across diverse photoredox reactions, including Minisci reactions, aryl amination, trifluoromethylation, radical sulfonylation, and dual Ni-catalyzed C–N, C–C, and C–S couplings. We further evaluate multiple recycling strategies, including precipitation, heterogeneous coating, and homogeneous recovery by nanofiltration. The PIM catalysts exhibit near-complete retention in nanofiltration, enabling the development of a continuous-flow reaction–separation system with in-line catalyst recovery and real-time process monitoring. This work establishes a platform for tunable, scalable, and recyclable photocatalysis and provides a blueprint for sustainable continuous-flow fine chemical manufacturing.