MOFs derived Ni-Mn bimetal nano-catalysts with enhanced hydrogen pump effect for boosting hydrogen sorption performance of MgH2

• Highly effective NiMn-MOF derivatives were synthesized using a one-pot method. • Peak dehydrogenated temperature of MgH 2 -NiMn-MOF derivative is 218.2 °C (3 °C/min). • The composite presents remarkable rehydrogenated ability at near room temperature. • The enhancing “hydrogen pumping” mechanism of Mg 6 MnO 8 and Mg 2 NiH 4 /Mg 2 Ni is revealed. In the present work, highly effective Ni-MnO binary nanocomposite catalysts were designed and synthesized using a one-pot method from Ni-Mn based bi-metal organic frameworks (MOFs). These nanocomposites were introduced into MgH 2 through ball milling as catalysts to enhance the hydrogen storage properties of MgH 2 . Through varying the Ni/Mn ratio in the bimetal MOFs, it is found that the Ni 1 Mn 1− MOF derived catalyst showed the best promotion effect on MgH 2 . The MgH 2 –10 wt.% Ni 1 Mn 1− MOF derivative demonstrated favorable overall performance with the low desorption peak temperature (218.2 °C) with a saturated hydrogen capacity of 6.42 wt.% and rapid hydrogen release/uptake kinetics. It can still reabsorb about 1.15 wt.% H 2 within 30 min at a temperature as low as 50 °C. Both performance tests (DSC and TPD) and structural characterizations (XRD, HRTEM, etc.) revealed that the synergistic role of in situ formed Mg 6 MnO 8 and Mg 2 NiH 4 /Mg 2 Ni phases for improving the hydrogen sorption properties of MgH 2 . Theoretical calculations reveal that Mg 6 MnO 8 destabilizes metal-H bonds in MgH 2 and Mg 2 NiH 4 , leading to an enhanced “hydrogen pump” effect of Mg 2 NiH 4 for MgH 2 . This research provides a strategy to rational design and preparation of bimetal MOF derivatives for the development of advanced hydrogen storage materials. The enhancing “hydrogen pumping” effect of in situ formed Mg 6 MnO 8 and Mg 2 NiH 4 /Mg 2 Ni on hydrogen storage performance of MgH 2 is revealed experimentally and theoretically.