Comparative study on carbon emission spatial network and carbon emission reduction collaboration in urban agglomerations

• Central cities have higher collaboration quantities and Anhui has higher intensity. • Carbon emission network shows core-periphery characteristics with growing complexity. • Mismatches exist between collaboration patterns and carbon emission network. • Collaboration exerts no significant impact on carbon emission network. Collaborative carbon reduction in urban agglomerations is imperative under China’s regional integration development strategy and dual-carbon goals. However, whether existing collaborative requirements align with the spatially networked reality of carbon emissions and deliver expected effects remains unclear, hindering deeper coordination. This study evaluates the status of carbon reduction collaboration in the Yangtze River Delta urban agglomeration through collaborative quantity and intensity dimensions. Social network analysis reveals the carbon emission spatial network structure, while a collaborative quantity/centrality versus intensity/centrality scatter plot assesses their alignment. QAP analysis tests collaborative efficacy. It finds that collaboration exhibits a core-periphery structure dominated by central cities, driven by inspections, framework agreements, and cooperation agreements, with peripheral cities compensating low participation through intensity-driven catch-up effects. The carbon emission network displays pronounced core-periphery characteristics with growing complexity, where core cities control regional emission flows while peripheral cities show limited influence, forming distinct net spillovers and agents. Mismatches exist between collaboration patterns and emission networks: central cities dominate cooperation, while peripheral cities lack initiative; intensity polarization and provincial-level mini-clubs prevail. Collaboration exerts no significant impact on emission network formation due to entrenched core-periphery power hierarchies.