The impact of industrial digital transformation on green development efficiency considering the threshold effect of regional collaborative innovation: Evidence from the Beijing-Tianjin-Hebei urban agglomeration in China

Promoting industrial digitalization and deepening regional collaborative innovation is essential for achieving urban green and sustainable development. This paper constructs a differential game model based on theoretical analysis and reveals the influence mechanism of industrial digitalization and regional collaborative innovation on urban green development efficiency (GDE). After that, this paper uses the entropy method, Super-SBM model, and improved gravity model to measure the level of industrial digitalization, urban GDE, and regional collaborative innovation, respectively. Then, this paper constructs the fixed-effects model, SDM model, moderating-effects model, and threshold model, then uses the panel data of the Beijing-Tianjin-Hebei (BTH) urban agglomeration during 2011–2020 for empirical testing. The results show that: (1) industrial digitalization significantly improves urban GDE. (2) Overall, 2011–2015 is the rapid development period of BTH industry digitalization, and 2015–2020 is its stable development period. However, there are apparent spatial differences and imbalances. (3) Industrial digitalization has a significant spatial spillover effect that can enhance local and surrounding cities' GDE. (4) Regional collaborative innovation can directly enhance urban GDE, and has a positive moderating effect on industrial digitalization to enhance urban GDE. (5) The regional collaborative innovation has two thresholds of 3.9851 and 6.6184. With the collaborative innovation level improving, the main effect intensity steadily increases.