Engineering cell membranes for catalysis is challenging due to their inherent complexity. Here we introduce a polymeric strategy to overcome these challenges by chemically modifying cell membranes with catalytic polymers, enabling robust, recyclable and photoenzymatic catalysis. Through a one-step in situ atom transfer radical polymerization on living Escherichia coli cells, polymers are generated to protect the cells from environmental stressors while facilitating chemoenzymatic synthesis by integrating catalytic polymers with intracellular enzymes. As a proof of concept, a photoenzymatic cascade with an anthraquinone-based polymer and benzaldehyde lyase is demonstrated, converting benzyl alcohol into benzoin and achieving bioconversion yields that are 15 times higher than controls. Additionally, cells serve as large biological scaffolds for polymers, enabling recycling of macromolecular catalysts. A recyclable chemoenzymatic system incorporating an organometallic polymer with intracellular enzymes is also presented. Our versatile, straightforward approach offers a technology platform for engineering cell membranes for cascade synthesis, with broad implications for synthetic chemistry, polymer chemistry and biotechnology.