The impact of urban digital economy on urban innovation: the mediating role of trade openness

The digital economy serves as a crucial driver of global economic growth and intercity connectivity. This study systematically examines the innovation effects of digital economic development through empirical analysis of panel data from 281 Chinese prefecture-level cities spanning 2011 to 2019, employing the spatial Durbin, mediation effect, and threshold regression models. The findings are as follows: (1) the digital economy significantly enhances urban innovation capabilities, with the magnitude of this effect exhibiting pronounced spatial heterogeneity-economically developed regions and large cities reap substantially greater innovation dividends compared to less developed areas; (2) spatial spillover effects display regional divergence: neighboring cities in eastern China benefit from statistically significant positive innovation spillovers, whereas central and western regions exhibit nonsignificant negative spatial correlations; (3) increased trade openness functions as a critical transmission channel for the digital economy to boost urban innovation, though this mediating mechanism operates exclusively in eastern regions and large cities, remaining inactive elsewhere; (4) the impact of digital economy development on urban innovation exhibits a single threshold effect. Trade openness moderates the impact of digital economy development on urban innovation, and this moderation follows an inverted U-shaped pattern.