Abstract:     As an essential governance tool for the implementation of China′s dual carbon target strategy, carbon trading policy is crucial to the green transformation and development of polluting enterprises. Facing the pressure of emission reduction, enterprises actively respond to the situation through many strategies such as R&D innovation, information disclosure and cost control, etc. Whether carbon performance can be effectively improved, its mechanism needs to be explored in depth. This paper took the data of Chinese listed companies from 2010 to 2018 as the research sample. Firstly, the difference-in-difference-in-differences (DDD) method was used to assess the impact of carbon trading policies on the carbon performance of polluting enterprises in general. Then, the mediating effect of R&D innovation was tested by the mediating effect model, and the difference of mediating effect under the heterogeneity of firm size was analyzed. Finally, the moderated mediating model was used to explore the moderating effect of information disclosure on the mediating effect of R&D innovation. The multiple mediating effect model was used to consider the comprehensive impact of compliance cost pressure and R&D innovation motivation on the carbon performance of polluting enterprises.
The main conclusions we have obtained from this study are as follows: (1) Carbon trading policy has a significant effect on carbon performance of polluting enterprises, and the findings remain valid through a series of methods such as common trend test, PSM-DDD, and replacement time window for robustness. (2) R&D innovation plays a partial mediating role in the relationship between carbon trading policy and carbon performance of polluting enterprises, and there is significant heterogeneity in the mediating effect. Compared with large-scale enterprises, the effect of R&D innovation on carbon performance of small-scale enterprises is more obvious. (3) Under the moderating effect of information disclosure, the mediating effect of carbon trading policy to enhance the carbon performance of polluting enterprises through R&D and innovation gradually increases. (4) Cost compliance pressure and R&D innovation motivation play multiple mediating roles in the relationship between carbon trading policy and carbon performance of polluting enterprises, in which the cumulative mediating role of cost pressure negatively overshadows the parallel mediating role of R&D innovation, so that the Porter effect of carbon trading policy has not yet appeared. And, the effect of carbon performance improvement is still in the stage of "cost compliance".
   The possible marginal contributions of this paper are as follows: (1) In the research design, carbon trading policy, R&D innovation and carbon performance of polluting enterprises are incorporated in the same analytical framework, focusing on the impact of carbon trading policy on carbon performance of polluting enterprises, adding new empirical evidence to the micro mechanism of carbon trading policy. (2) In terms of mechanism analysis, the moderated mediating model and multiple mediating model are innovatively introduced to explore the moderated mediating effect and serial mediating effect that may exist between carbon trading policy and carbon performance of polluting enterprises, broadening the micro channels for carbon trading to exert institutional dividends. (3) On the theoretical boundary, the Porter hypothesis is subdivided into the stage of cost pressure and innovation motivation. The impact of the combined effect of cost pressure and innovation motivation on the carbon performance of enterprises is considered comprehensively, to clarify the realization context of the Porter hypothesis on carbon trading policy and add new theoretical literature on whether the Porter hypothesis is valid and the conditions of its action.

Key words:  carbon trading policy, research and development innovation, carbon performance of polluting enterprise, difference-in-difference-in-differences (DDD) method, carbon peak and carbon neutrality