How does digital infrastructure affect industrial eco-efficiency? Considering the threshold effect of regional collaborative innovation

The implementation of Digital China and Made in China 2025 strategies has brought guiding the rapid development of digital infrastructure (DI) and industrial ecology into focus. Based on Beijing-Tianjin-Hebei (BTH) city data from 2011 to 2020, this study empirically investigates the influence mechanism and spatial effect of DI and regional collaborative innovation (RCI) on industrial eco-efficiency (IEE) using the improved gravity model and super-efficiency slacks-based measure model. The relevant findings are as follows: (1) Static and dynamic analyses show that DI significantly improves IEE. (2) The moderating effect test shows that RCI strengthens the effect of DI on IEE. (3) The threshold effect test captures a U-shaped nonlinear relationship between DI and IEE at different RCI intervals. In the positive stage, the improvement effect of DI on IEE presents marginal increasing characteristics. (4) For the spatial perspective test, the BTH city's DI and IEE exhibit a positive spatial correlation, and gradually form H-H and L-L cluster states. Furthermore, the city's DI improves the local city's IEE and benefits neighboring city's IEE, revealing spatial spillover effect. This study has valuable reference significance for other regions to simultaneously solve industrial development and environmental problems by advancing DI.