A smart city is a new, efficient, and technologically advanced city that integrates green and social development [1]. Such cities effectively alleviate the inability to process information related to urban environmental protection and resource utilization efficiency [2]. Through the full application of a new generation of information technology, smart cities can effectively optimize urban services and operations [3], alleviate the information processing capacity contradiction between urban environmental protection and resource utilization efficiency, and achieve the benefits of extensive informatization, industrialization, and urbanization [4]. With the rise of the internet and mobile technology, the smart city is an advanced form of information-based city development.

Owing to its potential advantages brought by digital technologies, the smart city has attracted the attention of many countries, such as the USA, Germany, Japan, and China [5]. However, some studies indicate that environmentally friendly smart cities may exacerbate urban pollution. For example, the large-scale information and communication technology (ICT) and industrial construction brought about by smart city policy (SCP) can lead to an increase in electricity consumption, which, in turn, increases carbon emissions [6]. Although the increases in ICT and internet penetration driven by SCP are not always beneficial to the environment, other studies indicate that, in general, smart cities positively impact the urban environment (e.g., carbon emission reduction) [7].

The above views are quite divergent, and the reason is that many influencing factors contribute to the total carbon emissions in a city. Among these, enterprises, which are the key drivers of an urban economy, generate most of the city’s carbon emissions. To some extent, the carbon emission intensity of enterprises directly determines that of the entire city. Therefore, it is necessary to study the impact of SCP on the carbon emission intensity of enterprises at the micro-level. Furthermore, it is worth noting that a smart city is a recently adopted concept that relies mainly on digital transformation to realize city smartness [8]. Digital technologies are closely associated with the concept of a smart city [9]. ResWearchers posit that the relationship between smart cities and digitalization can promote the adjustment of the city’s industrial structure, thereby influencing the city’s carbon emissions. This speculation is reasonable from a macro perspective, that is, thinking from the perspective of the whole city. However, does this speculation hold true for micro-enterprises in the city? In other words, does SCP influence the digital transformation of the micro-enterprise and subsequently impact its carbon emission intensity? Most mainstream research uses the construction of information infrastructure in a city to measure its degree of digital transformation. This method, however, does not adequately reflect the degree of digital transformation of urban enterprises.

2. Smart Cities and Ecological Environment

The prominent feature of smart cities is the application of ICT and the large-scale construction of related infrastructure. ICT represents the image and expectations of the future ^[10][11]. Building a smart city is one significant achievement in the path toward realizing sustainable urban development, which leads to the application of information technology and an increase in the overall competitiveness of cities ^[11][12]. Under rapid economic development, the deterioration of the urban environment caused by human activities has become a problem that cannot be ignored ^[12][13]. Therefore, smart cities have become a key direction in transforming urban development in many countries [5]. Regions with developed economies and rapid information technology development usually enjoy a high level of social informatization and digitalization. This means they have good basic conditions for smart development and relatively stable planning schemes for smart city construction. Developing a digitally driven smart city is an important way to promote green and sustainable economic growth [5]. Smart cities include the characteristics of urbanization (infrastructure construction) and informatization (digital facility construction and application) because, to a certain extent, they are a product of the combination of these two elements. Many scholars have researched the impact of urbanization on the environment. Urbanization is seen as an important factor in the soaring global energy consumption and the rapid increase in carbon dioxide emissions ^[13][14]. Early studies have found that, since urbanization often accompanies industrialization, there is a close correlation between urbanization and the greenhouse effect [1], which leads to increased urban pollution. Research in developing countries shows that the impact of urbanization on carbon emissions forms an inverted “U”-shaped relationship [6]. However, some scholars posit that environmental pollution will ease with urban expansion, mainly because wealthy cities can transfer part of the environmental cost to other regions ^[14][15]. In particular, urbanization measured by different indicators has various impacts on carbon dioxide emissions ^[13][14], which explains the differences in research conclusions regarding the impact of urbanization and carbon emissions. As mentioned, the smart city is the embodiment of in-depth contemporary urban development. Through the combination of the Internet of Things (IoT) and big data, smart cities have greatly promoted the use of professional technology to solve environmental pollution problems ^[15][16], which is crucial to urban development and planning ^[2][15][2,16]. Existing research can be divided into two categories. The first explores the factors that promote the construction of smart cities, primarily knowledge ^[16][17], IoT systems ^[5][7][17][5,7,18], and information technology construction ^[3][9][3,9]. The second focuses on the impact of smart cities on urban development. Representative studies have demonstrated the role of smart cities in promoting urban innovation ^[14][18][10,15] and urban competitiveness ^[11][12].

3. Smart City Policy and Digitalization

We should consider the potential influence that SCP will bring. The digital transformation of an enterprise refers to the application of digital technology and equipment in the process of business improvement ^[19][20][21][19,20,21]. Modern society has entered the era of the digital economy [20], and digital technology has significantly changed original production methods, business models, and organizational patterns and has even subverted basic assumptions in many innovation theories [21]. One of the salient features of smart cities is the large-scale application of digital and information technology [22], wherein digital technology and traditional production models are inter-embedded, and production resources are reorganized and optimized with the help of technological innovation [23]. The rapid development of the digital economy has also stimulated research on the digital transformation of enterprises; for example, Yoo et al. [20], Nambisan et al. [21], Li et al. [24], Libert et al. [25], Vial [26], and Nwankpa and Roumani [27]. 

4. Smart City Policy in China

It should be noted that the characteristics and effects of SCP may vary from country to country. SCP appears to be the “patent” of developed countries, as few developing countries implement it. China is among the few developing countries that implement smart cities, which provides a reference for in-depth research on the application of smart cities in different countries. China’s smart city construction began relatively late but has developed rapidly. In January 2013, the Ministry of Housing and Urban-Rural Development of the People’s Republic of China (MOHURD) announced China’s smart city pilot list, which included 37 prefecture-level cities, 50 districts (counties), and 3 towns. A total of 90 cities formed the initial wave of smart city construction in China. In March 2021, the 14th Five-Year Plan for the National Economic and Social Development of the People’s Republic of China and the Outline of Vision 2035, promulgated by the Chinese government, further emphasized the importance of building many smart cities. Since then, local governments have responded positively and have released development plans with the long-term goal of building smart cities by 2035. With the exception of Shaanxi and Jilin, the other 29 provinces have pointed to the importance of promoting smart city construction and improving the level of intelligence in social governance. At present, China is still promoting the construction of smart cities nationwide. Qian et al. [5] employed the PSM-DID method to study the impact of China’s SCP on economic green growth based on SCP implementation data. They found that smart cities can reduce urban unit gross domestic product (GDP), energy consumption, and waste emissions significantly. Xu et al. ^[18][10] and Xin and Qu [19] also used the PSM-DID method to study the impact mechanism of China’s smart city construction on the level of urban innovation and green total factor productivity. Yu and Zhang [4] examined the impact of China’s SCP on city-level energy emission intensity based on the DID method and found that smart city construction had a significant positive impact on city-level energy efficiency. The above studies analyze the impact of China’s smart cities on urban construction and future development from different perspectives and find diverse impacts of China’s SCP. The effects are more significant in China’s megacities and central cities.