How hydrogen bonding and - 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, pi-pi and hydrogen bonding interactions were proposed and verified from characterizations, comparative experiments and theoretical calculations. The synergistic effects of the hydrogen bonding and pi-pi interactions increased the adsorption energies from -15.26 kcal & sdot;mol(-1) to -21.83 kcal & sdot;mol(-1), enhanced the degree of pi-dissociation, enlarged the pi-pi isosurface area, extended the van der Waals surface mutual penetration distance, achieving stronger affinity and remarkable adsorption. Furthermore, offset (parallel-displaced) pi-pi 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 & ctdot;O and N-H & ctdot;O 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 mu g center dot g(-1), displayed excellent performance in wide pH range of 5 similar to 11 and in the coexistence of multi-chemicals.