How hydrogen bonding and π–π interactions synergistically facilitate mephedrone adsorption by bio-sorbent: An in-depth microscopic scale interpretation

Mephedrone (4-methylmethcathinone, MEPH) exhibited severe ecologic hazards and health detriments. A novel deep eutectic solvent functionalized magnetic ZIF-8/hierarchical porous carbon (DMZH) with excellent selectivity, interference resistance and recyclability, was developed for the rapid adsorption of MEPH. Initially, potential adsorption sites of MEPH were predicted. Then, π-π and hydrogen bonding interactions were proposed and verified from characterization, comparative experiments and theoretical calculations. The synergistic effects of the hydrogen bonding and π-π interactions increased the adsorption energies from −15.26 kcal⋅mol−1 to −21.83 kcal⋅mol−1, enhanced the degree of π-dissociation, enlarged the π-π isosurface area, shortened the van der Waals surface penetration distance, achieving stronger affinity and remarkable adsorption. Furthermore, offset (parallel-displaced) π–π stacking form existed between DMZH and MEPH. DMZH acted as the hydrogen bond donor and MEPH served as the hydrogen bond acceptor to form O–H⋯O and O–H⋯N hydrogen bonding interaction. Profiting from the synergistic effects, DMZH showed satisfactory adsorption for MEPH within 20 min with a maximum adsorption capacity of 3270.11 μg g−1, displayed excellent performance in wide pH range of 5∼11 and in the coexistence of multi-chemicals.