Preparation of metal-organic framework composite beads for selective adsorption and separation of palladium: Properties, mechanism and practical application

•A feasible and green method is developed to prepare novel MOF composite beads.•Entanglement networks and hydrogen-bond interactions are generated by PEI in B-MOF.•B-MOF exhibited high adsorption capacity (334.68 mg.g−1) and excellent reusability.•An efficient process for the recovery of Pd from industrial waste is established.•Inner-sphere complexation and electrostatic attraction are the main mechanisms.