In today\\\'s world, striking a balance between economic growth and environmental preservation has emerged as one of the most pressing challenges facing human societies. The Environmental Kuznets Curve (EKC) hypothesis posits a non-linear relationship between GDP and environmental pollution, suggesting that pollution initially rises with economic growth but begins to decline after a certain level of income is reached. However, the realization of this curve in various countries is influenced by several variables, including economic complexity, which reflects the diversity and advancement of a country\\\'s productive structures and technologies. This study aims to clarify the role of economic complexity in the relationship between economic growth and CO2 emissions by analyzing data from countries with high, medium, and low levels of natural resource rents. To this end, panel data from 40 countries with high natural resource rents from 2000 to 2021 were used and categorized into three groups based on their Resource Curse Vulnerability Index (RCVI). The study employs Necessary Condition Analysis (NCA) and fuzzy-set Qualitative Comparative Analysis (fsQCA) to identify the necessary and sufficient conditions that influence CO2 emissions. NCA reveals that in countries with high RCVI, variables such as economic complexity, GDP, and urbanization are necessary conditions for CO2 emissions. In contrast, fewer variables meet these criteria in countries with medium and low RCVI. The fsQCA identifies various causal configurations leading to high or low CO2 emissions across the groups. Notably, in high-RCVI countries, an increase in economic complexity, when combined with other factors, can lead to a reduction in CO2 emissions, aligning with the Environmental Kuznets Curve (EKC) hypothesis. For countries with medium and low RCVI, achieving lower emissions requires specific combinations of economic complexity, good governance, and the adoption of renewable energy. These findings suggest that a country\\\'s natural resource endowments moderate the environmental outcomes associated with economic complexity. Consequently, policymakers should tailor environmental strategies to their nations\\\' economic and resource contexts to effectively reduce CO2 emissions while fostering economic growth.

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