Molecular weight-engineered polyelectrolyte boosts charge carrier mobility for enhanced photocatalytic antibiotic removal.

In this research, we developed a high-efficiency photocatalytic system for antibiotic removal by controllably modifying black phosphorus (BP) with poly (diallyldimethylammonium chloride) (PDDA) of varying molecular weights, and subsequently integrating it with titania nanosheets (TNs) to form composite heterostructures. This molecular weight engineering strategy significantly enhances interfacial charge carrier transport and BP's environmental stability. Mechanistically, higher molecular weight PDDA creates more extensive interchain conductive networks, optimizing electron transfer pathways and suppressing charge recombination. The resulting F4-BP/TNs heterostructure achieved a tetracycline hydrochloride (TC) degradation efficiency of 97.4 % under visible light irradiation. Furthermore, its excellent stability was demonstrated by maintaining over 90 % degradation efficiency after four cycles. This work provides critical insights into the molecular weight-dependent mechanism of polyelectrolyte-mediated photocatalysis, offering a novel strategy for designing efficient and stable materials for environmental remediation.