High-Porosity Conjugated Polyelectrolytes Synthesized via Sonogashira–Hagihara Coupling in Concentrated Emulsions: Robust Adsorptive–Photocatalytic Hydrogels for Water Pollutant Removal

Conjugated polyelectrolyte (CPE) hydrogels uniquely combine π-conjugation, ionic functionality, and water compatibility in a single-polymer network. This work reports on the design, synthesis, and application of high-porosity CPE hydrogels obtained via the Sonogashira-Hagihara cross-coupling reaction as a polymerization chemistry in a high internal phase emulsion (HIPE) template. In this way, we combine the hydrophilic and π-conjugated electronic properties of CPEs with the high porosity of polymerized high internal phase emulsions (polyHIPEs or PHs), enabling the development of a multifunctional polymer platform. High-porosity CPE-PHs exhibit a surface area of up to 355 m²·g^-1, excellent water uptakes of up to ∼25 g·g^-1, and visible-light absorption with band edges at 720 and 610 nm and band gaps of 2.35 and 2.47 eV for anionic CPE-PH-SO₃® and cationic CPE-PH-NMe₃ ⁺, respectively. These CPE-PHs are then used to remove the endocrine-disrupting chemical bisphenol A (BPA) as a model water pollutant. The CPE-PH-SO₃® demonstrates exceptional performance, achieving overall removal efficiencies of 93% and 96% through synergistic adsorption (∼71% and ∼50%, respectively) and visible light-driven photocatalysis (∼22% and ∼46%, respectively) during 8 and 24 h experiments. These efficiencies are among the highest reported for organic photocatalyst. In contrast, the cationic analogue CPE-PH-NMe₃ ⁺ suffers from oxidative degradation and thus limited activity. Stability studies confirmed that CPE-PH-SO₃® retains its structural and electronic integrity during prolonged operation. These results demonstrate the potential of high-porosity CPE-PH hydrogels as a multifunctional polymer platform that synergistically integrates adsorption and heterogeneous photocatalysis for robust and efficient water applications.