In the context of global warming, many countries have announced their national targets in reducing their CO2 emissions. In order to evaluate the technology roadmaps that are necessary to achieve these targets of CO2 emissions, a flexible modeling framework is proposed in this article. This sectoral model avoids the complex computing operations and can be customized according to different requirements and situations. We simulate the model up to the horizon 2050, which is often seen as a turning point in energy use patterns worldwide (forced by the probable decline in hydrocarbons extraction). The technology roadmaps for governmental targets on CO2 emissions are studied for three typical countries: China, France, and the United States. The model covers the sectors responsible for the greatest part of CO2 emissions: power, transport, residence and industry sector, in studying the impacts of the principle energy technologies, such as energy mix, Carbon Capture and Storage, electric vehicles and energy efficiency. Different from classic cost-effective energy system models, our model provides the technology pathways for different criteria, such as balanced development of energy technology across sectors, availability of energy resources, etc. Besides, the sensitivity of parameters in the model is tested for robust simulations at each step of the work and for all technology roadmaps scenarios.