Research on the policy effect of the central bank giving priority to green bonds under the collateral framework

In order to promote the realization of the "dual carbon" strategic goals, the People's Bank of China has included green bonds in the medium-term lending facility (MLF) collateral framework and given it a priority status, marking a structural transformation of monetary policy tools in the green transformation. This paper focuses on the incentive mechanism and transmission path of this policy tool, analyzes the response behavior of commercial banks under the incentive of collateral policy and the constraint of default risk, and reveals the institutional advantages of green bonds in asset allocation and its risk boundary. On this basis, the synergy mechanism of green mortgage policy and carbon tax tools is further explored, and an optimization plan for the dual policy path of "incentive + constraint" is proposed. The study points out that while the green bond priority policy improves the efficiency of green capital investment, it needs to be combined with fiscal means to achieve a dynamic balance between policy effectiveness and financial stability. This paper has certain theoretical value and practical enlightenment for improving China's green financial system and enhancing the adaptability of policy tool combinations.