The construction of smart cities, as a key driving force for the low-carbon transformation of the economy, urgently needs a systematic assessment of its carbon emission reduction potential. Based on the panel data of 277 cities in China from 2007 to 2021, this study adopts innovative methods, integrates bibliometric analysis, and employs empirical models to deeply explore the impact of smart city construction on carbon emissions and its regional heterogeneity and resource endowment heterogeneity. The main findings are as follows: (1) The research on smart cities and carbon emissions present knowledge synergy, focusing on innovation and green development strategies. (2) A series of robustness tests show that smart city construction can significantly reduce urban carbon emissions. (3) Heterogeneity analysis reveals that the carbon emission reduction effect varies between regions (more significant in the northern region) and with resource endowments (non-resource-based cities are more advantageous). The important contribution of this study lies in its quantitative assessment of the carbon emission reduction effect of smart city construction, as well as its heterogeneity; this study also provides a solid empirical basis for formulating more targeted regional smart city development policies.