Technology transfer is essential for addressing technological disparities in urban areas and reducing carbon emissions. This study analyzes inter-city technology patent transfers and carbon emission data from China (2010–2019) using a spatial Durbin model to assess the effects of technology inflow and outflow on carbon emissions and their spatial spillover effects. Key findings include the following: ① a significant spatial correlation exists between technology inflow, outflow, and carbon emissions, with notable spillover effects; ② both technology inflow and outflow reduce intra-regional carbon emissions, but only outflow significantly reduces inter-regional emissions; ③ regional differences are evident, with the eastern and central regions showing significant reductions due to technology transfers, while the western and northeastern regions do not. In the northeastern region, technology transfer significantly aids neighboring cities in reducing emissions. However, the central region lacks spillover effects from outflow, and technology inflow and outflow in the western region hinder reductions. This paper provides policy recommendations to improve urban technology transfer and carbon emissions mitigation.

Technology transfer represents a critical avenue for addressing the challenges associated with carbon emission reduction, warranting thorough investigation into the effects of both domestic and international technology transfer on carbon emissions. This study employs data mining techniques to extract comprehensive data on patent transfers across 334 prefecture-level cities in China from 2000 to 2021, analyzing the influence of technology transfer on carbon emissions from both domestic and international perspectives. The findings indicate that domestic technology transfer and international technology transfer significantly contribute to carbon emission reduction, with international technology transfer exerting a more substantial effect than its domestic counterpart. To mitigate endogeneity concerns, the study utilizes the shortest distance from each city to the telegraph lines established during the late Qing Dynasty as an instrumental variable and the resulting conclusions remain robust. Heterogeneity tests reveal significant regional disparities, particularly in areas located southeast and northwest of the Hu Huanyong line, as well as between regions inside and outside the five major urban agglomerations. The mechanisms underlying carbon reduction suggest that improvements in energy efficiency and upgrades in industrial structure serve as the primary pathways for carbon emission reductions resulting from both domestic and foreign technology transfers. These conclusions provide a theoretical foundation and empirical insights to facilitate the acceleration of technology flow within the context of high-quality development, particularly concerning environmental protection.