Donor Geometry Engineering for Regulating Spatial Charge Distribution in Heptazine-Based D-A Porous Organic Polymers Toward Efficient Photocatalysis

Regulating the spatial charge distribution in donor-acceptor (D-A) porous organic polymers (POPs) to suppress charge recombination remains a formidable challenge in the field of photocatalysis. Herein, donor geometry engineering as a design method is proposed to address this issue. Three novel heptazine-based donor-acceptor porous organic polymers (D-A POPs) with varied fusion patterns and connection sites of the polycyclic aromatic hydrocarbons (PAH) donors have been constructed. DFT calculations reveal that the linear 2,7-bis(4-aminophenyl)pyrene donor in Py-2,7-Cy confines holes exclusively to the pyrene core and electrons dominantly to the heptazine acceptor, minimizing the wavefunction overlap, whereas hole delocalization to peripheral phenyl rings in Phe-2,7-Cy and Py-1,6-Cy leads to more significant overlap. Such geometry-dependent spatial separation of the photogenerated carriers in Py-2,7-Cy directly translates into a reduced exciton binding energy, suppressed charge recombination, and extended exciton lifetimes. Consequently, Py-2,7-Cy achieves 95% conversion of methyl phenyl sulfide dramatically outperforming Phe-2,7-Cy (12%) and Py-1,6-Cy (25%) under the same conditions, and exhibits excellent recyclability and broad substrate scope. This work establishes that donor geometry engineering is a powerful method to tune the charge dynamics in D-A POPs.