Stimulate synergistic efficiency of pollution-carbon Co-control in the digital era: The role of digital trade in cities

As micro-nodes in the global economic network, cities are hubs of both human activity and industrial production. Cities act as the main space of ecological pollution while hosting the most pollution-exposed population, which is a structural paradox that continues to challenge green urban development. The ongoing digital transformation of urban industrial structures and daily practices, presents new opportunities for cities to pursue more sustainable development paradigms. This study focuses on the role of digital trade in enhancing the synergistic efficiency of pollution control and carbon reduction via panel data covering 283 Chinese cities. The empirical results indicate that the leap of digital trade significantly advances the synergistic efficiency of pollution-carbon co-control, with an improvement equivalent to about 20% of the variation range in the synergistic effect. Mechanism analysis reveals dual transmission channels—regional innovation capacity strengthening (contributing 13.33% of total effects) and factor market distortion alleviation (accounting for 24%). The heterogeneity effect exists across cities, and digital trade shows larger green and low-carbon dividends in free trade zones, industrially developed cities and large-scale cities. Crucially, panel threshold regression identifies the optimal level of digital trade for green, low-carbon development (threshold = 0.139), beyond which energy-intensive scale-up offsets 29.27% of the initial environmental gains—a phenomenon known as the green efficiency paradox. Regional ecological governance should leverage digital trade to support green transition, strategies should align with local industrial base. Corresponding policies should be placed on fostering innovation and optimizing factor market to maximize environmental gains.