Do smart cities promote a green economy? Evidence from a quasi-experiment of 253 cities in China

China's carbon neutrality target is not only a new requirement for energy development, but also a guide for the green and low-carbon development mode and direction of the whole economy. In order to achieve green and low-carbon goals, promote the construction of ecological civilization, and realize high-quality urban development, the Chinese government proposed the construction of “smart cities” in 2012. Using data from 279 cities in China from 2008 to 2020 and a multi-period difference-in-differences method, this paper empirically tested the impacts of the smart city constructions on the development of urban green economy. The results show that: the implementation of smart city has a significant impact in promoting the development of urban green economy, which is manifested in significantly reducing the pollutant emissions and energy intensity and has regional heterogeneity; Endogeneity issues arising from pilot selection are effectively addressed with the help of instrumental variables; Furthermore, the impact mechanism of smart city on green economy is also analyzed.