Molecular structure characterization of coal under the water–rock interaction in acid mine drainage (AMD)

•The test AMD environment is closer to the actual production than ever before.•It fills the gap in the change characteristics of coal molecular structure under the action of AMD.•Obtained the characteristics of AMD acidity on the molecular structure of coal.•Obtained the characteristics of AMD soaking time on the molecular structure of coal.•The results provide theoretical support for the study of macro-physical properties of coal under AMD environment.