The interactions between CO

2

and coals during CO

2

-ECBM (CO

2

sequestration in deep coal seams with enhanced coal-bed methane recovery) could change pore morphology and chemistry property of coals

thereby affecting adsorption

diffusion and flow capability of CO

2

and CH

4

within coal reservoirs. To simulate CO

2

-ECBM process more practically

the dynamic interactions of supercritical CO

2

(scCO

2

) and moisture-equilibrated coals were performed at temperature of 318.15 K

pressure of 12.00 MPa

and duration of 12.00 h. The impacts of the interactions on physicochemical properties of coals were investigated. Results indicate that scCO

2

/H

2

O exposure shows minor effect on micropores of coals. However

the exposure significantly decreases the mesopore surface area of bituminous coals

while increases that of anthracites. The mesopore volume and the average mesopore diameter of all the coals after scCO

2

/H

2

O exposure decrease. The multi-fractal analysis verifies that the scCO

2

exposure

can enhance the pore connectivity of various rank coals. Apart from the pore morphology

the exposure of scCO

2

/H

2

O also affects the oxygenic functional groups on coal surface. Particularly

the exposure of scCO

2

/H

2

O reduces the content of CO and CO of coals. The content of COOH of low rank coals including Hehua-M2# coal

Zhongqiang-4# coal

Buliangou-9# coal and Tashan-5# coal decreases

while the high rank Laochang-11# coal and Kaiyuan-9# coal witness a growth in COOH. The content of total oxygenic functional groups of all coals after interaction with scCO

2

/H

2

O decreases; on the contrary

that of CC/CH of all coals after scCO

2

/H

2

O exposure increases. In summary

the interaction with scCO

2

/H

2

O significantly changes the pore system and oxygenic functional groups of various rank coals

which needs further attention regarding CO

2

-ECBM.