This study builds a Computable General Equilibrium model to investigate the synergistic effects and simulate the co-benefits of carbon tax policies. The conclusions are as follows: After implementing a carbon tax policy, when the carbon tax increases from 30 CNY/ton to 130 CNY/ton, and the reduction in CO₂ emissions increases from 1.223 billion tons to 3.943 billion tons. At the same time, the reduction in SO₂ emissions rises from 326,200 tons to 1,052,200 tons. However, overall, the reduction rate of SO₂ is around 88.87% of the CO₂ reduction rate. Thus, a carbon tax is also an effective policy pathway for synergistic pollution reduction and carbon mitigation. In terms of industry output, among the 15 industries, sectors such as electricity generation, aviation, and tertiary industries have increased their output, with the electricity sector achieving the highest increase of 2.9816%. Other industries have exhibited varying degrees of decline, especially coal, natural gas, oil, nonferrous metals, chemicals, steel, and building materials, with the coal industry output decreasing the most, by −49.4924%. Regarding energy consumption, as the carbon tax increases, the consumption of coal, oil, and natural gas all show a downward trend, with coal experiencing the largest decrease, at −49.5640%.

China’s approach to air pollution control has been shown successful in East Asian countries and even elsewhere in the world. The analysis of the evolution and control of air pollution in China over the past 75 years can be used as a reference for developing countries suffering from air pollution resulting from urbanization. Based on the sorting and mining of relevant indicators, data and policy texts from the areas of population, economy, space and social urbanization, the findings suggest that the presence of air pollution and its changing forms indeed have complex interactive relationships with the process of urbanization. Specifically: (1) the feature of air pollution has changed from “single pollutant and pollution source to multiple pollutants and pollution source, local pollution to regional pollution, light pollution to heavy compound pollution” as a result of urbanization, the emphasizing of construction and the neglect of governance, the emphasizing of economics and the neglect of ecology, and the emphasizing of immediate interests over long-term interests; (2) the interactive relationship between air pollution and urbanization has also gone through three stages from being irrelevant each other to “urbanization determines air pollution” and then “air pollution restricts urbanization”; (3) this has forced air pollution control to shift from the traditional “treating symptoms” to “high-quality urbanization”, thus promoting air pollution and urbanization to move “from confrontation to unification”. Therefore, air pollution control is not a simple technical issue; one of the keys lies in exploring how to adjust the urbanization model, so as to achieve the “win–win” of urbanization and air pollution control.

The essence of free trade zones lies in addressing development challenges through institutional opening-up and innovation-driven growth. Sustainable development constitutes the fundamental goal of free trade zone construction, opening-up and innovation serve as the core driving forces for their development, and a sound business environment acts as a critical guarantee for their efficient operation. Therefore, based on the panel data of 22 free trade zones in China from 2013 to 2022, this paper adopts Principal Component Analysis (PCA) and Analytic Hierarchy Process (AHP) to conduct a comprehensive evaluation of their sustainable development levels from six dimensions: environmental optimization, economic development, opening-up, radiation-driven capacity, business environment, and scientific and technological innovation. The results indicate that, first, the overall comprehensive scores of free trade zones in sustainable development show an upward trend with obvious regional divergence in growth rates. Coastal free trade zones maintain robust growth momentum, inland ones achieve steady progress, and border free trade zones witness modest growth. Second, the comprehensive scores of the 22 free trade zones in 2022 present a gradient distribution, reflecting prominent regional development imbalance. On this basis, targeted policy recommendations are put forward in this paper.

This paper aims to scientifically evaluate the sustainable development level of China’s pilot free trade zones (FTZs) and provide empirical support for policy optimization. Taking 22 Chinese FTZs from 2013 to 2022 as research samples, we construct a six-dimensional evaluation system, including environmental optimization, economic development, opening-up, radiation-driven capacity, business environment, and scientific and technological innovation, and use principal component analysis (PCA) and analytic hierarchy process (AHP) for comprehensive measurement. The results show the following: (1) The overall sustainable development level of FTZs presents an upward trend with significant regional differences—coastal FTZs grow rapidly, inland FTZs grow steadily, and border FTZs grow slowly. (2) The 2022 comprehensive scores show a gradient distribution, and regional development imbalance is prominent. (3) Economic development and opening-up are the core driving dimensions, while environmental optimization and radiation-driven capacity have relatively low weights and weak contributions. The marginal contribution of this paper is the construction of a multi-dimensional standardized evaluation system for FTZ sustainable development and clarification of regional differentiation characteristics and driving mechanisms. Based on this, this paper puts forward targeted policy suggestions: implementing differentiated empowerment according to coastal, inland and border FTZ positioning, promoting cross-regional experience sharing, and establishing a dynamic monitoring mechanism to narrow the development gap and achieve high-quality coordinated development.