Assembling lignin carbonized polymer dots with bimetallic layered hydroxides to bridge water purification and zinc-ion storage

Achieving multifunctional lignin-based carbonized polymer dots (CPDs) with controlled structures lie at the forefront of energy-environmental materials, yet tackling the structure-activity relationship is needed to optimize the assembling design in diverse applications. Here we report a bifunctional dot-sheet heterostructure of intercalating lignin-CPDs into layered double hydroxides (CoNi-LDH) to link Fenton-like water purification and zinc-ion hybrid capacitors (ZIHCs). The amino-functionalized CPDs hold the binding abilities of metal-ions over a wide concentration, posing the potentials to coordinate bimetallic hydroxides. Benefiting from high graphitization and conductivity, the green-emitting CPDs are paired with CoNi-LDH to enhance the interlayer spacing, rapid ionic-inserting transfer, and reversible chemical adsorption. In a three-electrode system, the CoNi-LDH@CPDs exhibit an ultrahigh specific capacitance of 1553.2 F g⁻¹ at 1 A g⁻¹ with excellent rate performance (70.82% capacitance retention at 10 A g⁻¹). Thanks to the optimized geometric and electronic structure, intensified active sites and specific surface area, the CoNi-LDH@CPDs can activate percarbonate to eliminate antibiotic (∼94.44%) via reactive oxygen species and direct electron transfer paths over the entire pH of 3−11, with a robust stability of up to 82.16% even after ten consecutive cycles. After a low-temperature functionalization, the phase transition of layered metallic oxides (CoNi-LMO) is taken place onto the CPDs, which expedites high conductivity and abundant redox active sites to serve as the cathode of ZIHCs. It delivers a superior energy density of 122.97 Wh kg⁻¹ at 1050 W kg⁻¹ with a potential window of 2.1 V, and a long-term cycling durability of 98.89% even at a current rate of 20 A g⁻¹. Our work not only advances the synthesis of CPDs from renewable lignin but also provides the insights into optimizing CPDs-intercalated LDH materials for multifunctional pollutant dissociation and energy storage.