Sci-Tech Finance and Sustainable Urban Transition: Evidence from Pollution–Carbon Reduction Synergy and Green Growth in Chinese Cities

Reconciling pollution–carbon reduction with green growth is a central challenge for sustainable urban transition, yet the role of innovation-oriented financial policy in this process remains insufficiently understood. This study uses China’s sci-tech finance pilot policy (STFP) as a quasi-natural experiment and applies a multi-period difference-in-differences model to panel data for 284 prefecture-level cities from 2008 to 2023. The baseline results show that STFP significantly reduces the pollution–carbon synergistic pressure index (PCSP) and improves the green growth efficiency index (GGEI). Specifically, the policy reduces PCSP by approximately 8.10% and increases GGEI by 0.0350 units. These conclusions hold after a series of robustness and endogeneity tests. Mechanism analysis reveals that STFP works through three pathways: stimulating green industrial entrepreneurship, promoting green and digital technological innovation, and inducing the agglomeration of capital, talent, and technology factors. Heterogeneity analysis shows that the policy effect is more pronounced in large cities, cities with stronger collaborative governance capacity, and cities with better innovation environments. Spatial analysis reveals that STFP significantly reduces PCSP in neighboring cities, but has no significant spatial spillover effect on GGEI. Further analysis shows that STFP strengthens the coordinated improvement of pollution–carbon reduction and green growth. Policy-interaction analysis indicates that the Zero-Waste City pilot enhances the effect of STFP, whereas green finance policy exhibits a marginal substitution effect. This study provides city-level evidence on how sci-tech finance can serve as an institutional instrument for coordinating environmental governance and green growth in sustainable urban transition.