Ultrathin nickel-based metal–organic framework nanosheets (Ni-UMOFNs) were formed from NiCl2·6H2O and benzene-1,4-dicarboxylate through a sonication exfoliation method. In Ni-UMOFNs, the Ni atoms are octahedrally coordinated by six O atoms to form pseudo-octahedra which are further edge/corner connected with each other to form 2D layers separated by benzene-1,4-dicarboxylate linkers. On the Ni-UMOFN surfaces, Ni centers are partially five coordinated owing to the termination of benzene-1,4-dicarboxylate ligands, and these coordinated unsaturated metal sites can be used as catalytic active sites. In this work, Ni-UMOFNs were utilized as ethylene dimerization catalysts in the presence of an alkylaluminum cocatalyst for the first time. The Ni-UMOFN catalytic system showed moderate catalytic activity but high selectivity to 1-butene up to 92.8% under optimal conditions. The optimal Ni-UMOFN catalyst can be reused at least four times without considerable loss in the catalytic activity and selectivity to 1-butene. Extraordinarily, the outstanding level of reusable property is due to continuous exposure of fresh unsaturated metal active sites when the original metal centers on the catalyst surface are used and exfoliated, just like a snake’s molting.

Magnesium hydride is considered as a promising candidate for hydrogen storage; however, the sluggish kinetics and thermodynamic stability seriously obstruct its industrial applications. Hence, in order to improve the hydrogen storage performances of magnesium hydride, NiS@C additive was ball-milled with Mg powder to build NiS@C/Mg. The MgH2/Mg2NiH4 polyphase hydrides were in situ formed after hydrogenated activation and turned into Mg/Mg2Ni phases during the dehydrogenation process, establishing a cycle of hydrogen absorption and desorption. The NiS@C/Mg composite showed enhanced de/hydrogenation rates: it could quickly absorb 6.02 wt % H2 within 5 min at 250 °C and desorb 5.34 wt % H2 at 300 °C. Moreover, even at the temperature of 50 °C, it could reach 3.23 wt % hydrogen absorption capacity, and the apparent hydrogen desorption activation energy for MgH2 decreased to 60.45 kJ mol–1. It also delivered a high cyclic stability performance of 98.9% for hydrogen absorption and 98.5% for hydrogen desorption after 50 cycles. The enhanced de/absorption kinetics of NiS@C/Mg were ascribed to the synergistic effects of multiple-phase MgH2/Mg2NiH4 hydrides and the in situ formed MgS catalyst, and the existence of C also effectively prevented the passivation and agglomeration of multiple-phase particles. The method of in situ generating of multiple-phase hydrides and catalysts provides a new view for the preparation of high-performance hydrogen storage materials.

MIL-100 and MIL-101 were synthesized and evacuated to generate a series of heterogeneous catalysts for isomerization of 1-butene. Their crystal structures and pore properties were characterized by PXRD and nitrogen adsorption−desorption techniques. These catalysts showed high catalytic activity for isomerization of 1-butene and high selectivities for 2-butene at room temperature. Moreover, the MIL-101 (Cr) catalyst evacuated at 200 °C exhibited the largest BET surface area of 2759 m 2 g −1 . At the same time, conversion of 1-butene and the highest selectivity to 2-butene were up to 93.38% and 98.08%, respectively. This work indicated that MOFs containing coordinatively unsaturated metal sites might be promising catalysts for olefin isomerization under mild conditions.