Asymmetric Dual Sites Enable Spatially Resolved Biradical‐Mediated C–N Coupling for N,N‐Dimethylformamide Photoelectrosynthesis

N,N‐dimethylformamide (DMF) is a quintessential industrial solvent and precursor, and its energy‐intensive, high‐temperature conventional synthesis necessitates the development of mild, sustainable biomass‐derived alternatives. Photoelectrocatalysis (PEC) offers a promising green route; however, its performance is limited by competitive adsorption and inadequate control over reaction selectivity. Herein, we engineered an asymmetric dual‐site earth‐abundant semiconductor to achieve biradical‐mediated C–N coupling, attaining a Faradaic efficiency of 86.6%, a selectivity of 90.1%, and a DMF yield of 145.5 mmol m −2 h −1 . For practical implementation, the parallel‐connect stacked PEC device, with an area of 175 cm 2 , was recorded as the state‐of‐the‐art PEC system for DMF photoelectrosynthesis. Mechanistic investigations revealed that bismuth vacancies, possessing a high p‐band center, preferentially activated methanol to generate *CHO radicals, whereas BiO x sites, characterized by a moderate electronic environment, selectively catalyzed dimethylamine to form *N(CH 3 ) 2 radicals. This dual‐site architecture effectively decouples the competitive adsorption of alcohol and amine substrates, enabling spatial segregation and achieving biradical‐mediated C–N coupling. Importantly, the system demonstrated broad substrate adaptability, including cyclic secondary amines, highlighting its potential for constructing valuable amide derivatives. Our work provides a practical strategy for the mild valorization of biomass feedstocks and establishes an electronic structure‐guided paradigm for selectivity control and kinetic optimization in biradical‐mediated C–N coupling.