## 1 Introduction  
In China, the exploration, development, and use of coalbed methane has been paid more and more attention to in recent years. Although coalbed methane resources are very rich in China, the output of coalbed methane shows a steady downward trend [1]. A great amount of coalbed methane is stored in the coal seam damaged by action of tectonic stress. The effect of tectonic stress causes the damage and transformation of coal body structure, and thereby induces the tectonically deformed coals [2; 3; 4]. However, \"two high and two low\" characteristics of tectonically deformed coals, i.e., high gas content, high gas desorption rate, low permeability, and low coal strength, cause the dangerous areas of gas outburst in the tectonically deformed coal development areas, and thereby restrict the efficient exploitation of coalbed methane [5; 6]. Since the coal has larger adsorption capacity of CO2 compared to CH4, the replacement effect by injecting CO2 into the coal seam can enhance the recovery rate of coalbed methane (CO2-ECBM) and reduce greenhouse gas emissions effectively [7]. Therefore, CO2 adsorption characteristics of tectonically deformed coal is one of key problems during the coalbed methane exploitation by CO2 injection.  
The gas in coal mainly at adsorption state occurs on the inner surface of coal matrix particles. Therefore, the pore structure is an important factor affecting the gas adsorption characteristics of coal. Many previous studies have indicated the relationship between pore structure and gas adsorption of coal [8; 9]. Meanwhile, they have proposed that the coal adsorption is affected by coal pore volume, pore area, pore size, pore shape, and pore complexity, and revealed that developmental characteristics of micropores or nanopores are main factors affecting coal adsorption capacity to a large extent. For example, [PERSON] et al. [10] found that the adsorption capacity of coal was proportional to the micropore volume. [PERSON] et al. [11] believed that the specific surface area of nanopores determined the adsorption capacity of coal. [PERSON] et al. [12] studied the relationships between the pore structure and adsorption characteristics of low rank coal, and found that developmental characteristics of microporous pore volume determined change laws of gas adsorption characteristics.  
At present, there have been some studies on tectonically deformed coal adsorption, and some basic laws have been instituted. It has been found that the adsorption capacity of tectonically deformed coal is significantly greater than that of primary coal at the same coal rank, which is attributed to significant changes in pore volume and the specific surface area of micropores, as well as the developmental degree and connectivity of pore fractures of coal suffering from tectonic stress [13; 14]. However, there are still many problems to be investigated related to the CO\({}_{2}\) adsorption characteristics of tectonically deformed coal. For example, what are basic laws of CO\({}_{2}\) adsorption characteristics of tectonically deformed coal? How do vary the CO\({}_{2}\) adsorption capacity with increasing coal deformation degree? What are the evolutionary characteristics of nanopores of coal with coal deformation degrees, and their effects on the CO\({}_{2}\) adsorption?  
Therefore, tectonically deformed coals with different deformation degrees and deformation types are chosen as the research object. Isothermal adsorption experiments and pore structure tests and analysis were carried out to reveal evolution laws of CO\({}_{2}\) adsorption and nanopores with coal deformation degree. Finally, the control mechanisms of nanopore structure evolution on CO\({}_{2}\) adsorption of tectonically deformed coals were investigated.