Pyridinic-N-Doped Nanographdiyne: Site-Specific Synthesis and Proton-Coupled Electron Transfer in Oxygen Reduction

Nanographdiyne (nanoGDY), as an atomically precise molecular fragment that faithfully mimics the graphdiyne lattice, provides a well-defined platform for elucidating structure-property relationships in carbon-based materials. However, controlled heteroatom doping of nanoGDY with uniform and structurally identifiable active sites remains a fundamental challenge. Herein, we report a bottom-up synthetic strategy-via stepwise cross-coupling and intramolecular cyclization-that enables site-specific incorporation of pyridinic nitrogen into the nanoGDY skeleton, affording py-NGDY with a homogeneous, single pyridinic N configuration. The resulting material adopts an AA'-stacked layered structure with uniformly distributed pyridinic-N sites, as supported by X-ray diffraction and high-resolution electron microscopy. Spectroscopic and computational studies reveal that nitrogen substitution breaks the frontier-orbital degeneracy of the pristine framework, introducing an intramolecular charge-transfer character that distinctly modulates optical absorption and fluorescence dynamics. Electrochemically, py-NGDY shows enhanced oxygen reduction reaction (ORR) activity relative to the undoped o-TBGDY control, with an electron transfer number of 2.51, indicating a predominantly two-electron pathway with a modest four-electron contribution. pH-dependent differential pulse voltammetry establishes a PCET process with a 1e-/1H+ stoichiometry, while density functional theory identifies the ortho-carbons adjacent to pyridinic N as the catalytically active sites, distinct from the proton-accepting function of the pyridinic nitrogen. This work establishes a robust synthetic route to heteroatom-doped nanographdiynes and provides molecular-level insights into the PCET mechanism, offering a versatile platform for the rational design of carbon-based energy materials.