Steering Electron Transport in Intrinsically Piezoelectric Covalent Organic Frameworks for Efficient CO₂ Reduction

Photocatalytic CO₂ reduction represents a transformative route to sustainable fuels, yet remains limited by sluggish charge separation and rapid carrier recombination. Here, an intrinsically piezoelectric porphyrin-based covalent organic framework anchored with zinc single atoms (Zn-Por-COF) is used to promote directional charge transport and accelerate reaction kinetics. Zinc coordination (d¹⁰ configuration) induces local symmetry breaking in the framework, giving rise to an internal piezoelectric field that cooperates with a donor-acceptor conjugated network inspired by natural photosynthetic systems. Under combined light and ultrasound excitation, the strain-induced piezo-potential facilitates persistent charge separation and suppresses recombination. Ultrafast femtosecond transient absorption spectroscopy demonstrates that Zn incorporation effectively inhibits phonon-assisted nonradiative decay and prolongs the carrier lifetime to 226.0 ps, which is attributed to the formation of long-lived shallow trap states and improved exciton delocalization across the π-conjugated backbone. Consequently, Zn-Por-COF achieves a high CO evolution rate of 15.59 mmol g^-1 h^-1 during piezo-photocatalytic CO₂ reduction. This work demonstrates that intrinsic piezoelectricity in COF provides an effective strategy to regulate charge dynamics for high-efficiency light-driven CO₂ reduction.