Precursor polarization-directed crystallization of polymeric carbon nitride for solar-driven H2O2 synthesis and sustainable LiCoO2 recycling

Achieving high crystallinity in polymeric semiconductors is crucial for enhancing charge transport and optoelectronic performance. However, this remains a challenge due to the inefficiency of energy coupling during polymerization. Here, we introduce a precursor-polarization approach to improve the crystallinity of polymeric carbon nitride. By protonating the melem precursor, we generate highly polar -NH 3 ⁺ edge groups that significantly increase the microwave response and facilitate directional thermal activation during polycondensation. This polarization-mediated energy coupling accelerates the condensation process, yielding carbon nitride with improved crystallinity and charge transport properties. As a result, the material exhibits a tenfold increase in photocatalytic H 2 O 2 production compared with conventional microwave-generated carbon nitride, with an apparent quantum efficiency of 5.63% at 420 nm. Importantly, the photogenerated H 2 O 2 is directly applied to dissolve spent LiCoO 2 cathodes, demonstrating a solar-driven, environmentally benign strategy for lithium-ion battery recycling. This study establishes precursor polarization as a general design principle for controlling the crystallization of polymeric semiconductors and translating their optoelectronic advantages into sustainable chemical process.