How Can Digital–Real Economy Integration Affect Urban Green Innovation? Evidence from China

As the integration of the digital economy into the real economy accelerates and the goals of green and low-carbon development become increasingly clear, promoting green innovation (GI) through digital–real economy integration (DRI) is of great practical significance for achieving green, high-quality urban development. This study, based on a sample of 284 prefecture-level cities and above in China, used the entropy method to measure the development levels of the digital economy and real economy in each city and employed a coupling coordination model to calculate the degree of DRI. By constructing a bidirectional fixed effects model, a mediation effect model, a threshold regression model, and a spatial Durbin model, this study explored the impact of DRI on GI in cities. The research found that DRI has a non-linear promoting effect on GI. When a city’s DRI level surpasses the second threshold, each 1% increase in DRI leads to a 1.439% rise in GI. This effect also shows heterogeneity based on city location and resource endowment. In this process, transaction costs and the upgrading of the industry structure serve as mediating factors, with each 1% increase in DRI reducing transaction costs by 0.163% and enhancing industrial upgrading with a coefficient of 0.176. Additionally, DRI in one city can significantly enhance the level of GI in neighboring cities through spatial spillover effects. For instance, under the geographic distance weighting matrix, the indirect effect of DRI reaches 4.693, and similar significant spillover effects are observed under the economic distance and economic geography weighting matrices.