Owing to the increased greenhouse gas emissions and threat of environmental pollution, scholars have drawn attention to the issue of energy efficiency in recent decades. One of the main practical policies related to energy efficiency is deploying green tax and green financing tools. The main purpose of this paper is to analyze the impacts of issued green bonds and environmental taxes on energy efficiency in the 27 European Union (EU) member states from 2010 to 2021. The major results confirm that green bonds accelerate the process of improvement of the level of energy efficiency in EU members. In the EU, environmental taxation is an efficient fiscal policy to encourage enterprises to conduct different policies and projects to improve their energy efficiency levels. In addition, a 1% increase in the gross domestic product leads to an increase in energy efficiency of the EU by nearly 0.39%. The recommended practical policies are promoting the green bond market through more transparency and marketing among private investors, paying attention to the concept of green economic recovery, and issuing digital green bonds (DGBs).

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<abstract> <p>Interconnection is the priority direction of the Belt and Road initiative, which can provide substantial assistance to win-win cooperation. This study establishes a new indicator system from the five dimensions of policy, infrastructure, trade, finance, and people-to-people, evaluates the connect index of 63 Belt and Road countries from 2013 to 2020 based on the DEMATEL-ANP method which removes the potential subjective interference and interaction between indicators, and predicts the trend of the connect index by using the grey model. The findings indicate that the five dimensions of the Belt and Road connectivity have unevenly developed, among which the policy coordination has achieved the least. Singapore, Russia, and Malaysia have the highest connect index, and we can find that the 10 countries with the highest connect index are basically from East Asia &amp; Pacific and Europe &amp; Central Asia, which possess large economic and geographical differences. Moreover, there are 17 "omission areas" characterized by low national income, poor infrastructure, low population density, and small land areas along the Belt and Road. Finally, the Silk Road Economic Belt is facing structural imbalances in connectivity, and the relation features "proximity but not affinity" between China and its neighboring countries. These conclusions are friendly cautions and have constructive policy implications for the Belt and Road countries to achieve high-quality interconnection.</p> </abstract>

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