How Does Smart City Construction Affect Urban–Rural Collaborative Development? A Quasi-Natural Experiment from Chinese Cities

In recent years, smart city construction has brought significant social and economic impacts to emerging economies, especially in narrowing the urban–rural gap. However, there is relatively little empirical research on this aspect. We take China as an example for research. This study uses a Spatial Multi-period Difference-in-Differences (DID) approach to investigate the relationship between smart city construction and urban–rural collaborative development in Chinese cities, taking digital infrastructure as the mechanism variable. Our findings reveal that smart city construction significantly promotes urban–rural collaborative development and exhibits positive spatial externalities. These results remain robust after parallel trend tests, placebo checks, and controlling for other policy interferences. Further analysis suggests that this effect operates largely through the reinforcement of digital infrastructure, whereby the smart city initiatives enhance connectivity and interaction between urban and rural areas, fostering collaborative development. Moreover, the efficacy of smart city policies is found to be particularly prominent in cities with strong economic development, weak levels of urban–rural collaborative development, and high degrees of digitization. By illuminating the role of smart city construction in propelling urban–rural collaborative development, this study provides valuable insights for policymakers.