Catalytically Active Dynamic Phase‐Separated Coacervates

Liquid–liquid phase separation (LLPS) has emerged as a key organizing principle in biology, driving the formation of membraneless organelles that regulate cellular processes through spatial and temporal compartmentalization. Among essential biochemical functions, covalent catalysis plays a central role in metabolic transformations, yet its implementation within LLPS‐based systems remains largely unexplored. In this study, we report an ATP‐based coacervate system (Coa‐BATP) that mimics both the compartmentalization and dynamic responsiveness of biological LLPS, enabling significantly enhanced covalent catalysis. Coa‐BATP efficiently encapsulates a broad spectrum of small molecules, including hydrophobic substrates, and promotes hydrazone formation, a C─N bond‐forming reaction, with nearly 300‐fold rate enhancement. This pronounced catalytic efficiency arises from the combined effects of elevated local concentrations of reactants within the coacervate matrix and the nucleophilic character of amine‐rich branched polyethylenimine (BPEI), which actively participates in the reaction. A hallmark of living systems is their ability to dynamically respond to environmental and biochemical cues. Coa‐BATP reversibly assembles and disassembles in response to enzymatic ATP hydrolysis by alkaline phosphatase, thereby switching catalytic activity on and off. These findings open new avenues for the design of protocells and synthetic organelles, with broad implications for prebiotic chemistry, artificial cell engineering, and synthetic biology.