Search

Catalytic efficiency is crucial to a reaction system and is intrinsically related to the physical and chemical conditions. One of the challenges to enhance the catalytic efficiency has been the limited activity of metal catalysts for their state transformation. Usually, metal centers in homogeneous systems show better catalytic activity than their heterogeneous counterparts but lower stability due to the thermodynamic instability. Combining the features of both systems, herein, we report the "homogenization of heterogeneous catalysis" to illustrate the state transformation of Pd(II)x-UiO-67-bpy, which exhibits good catalytic properties and stability in the cyclization of isonitriles with N-acyl-o-alkynylanilines. The regulation of UiO-67-bpy on palladium active species at different stages of the reaction time realizes the efficient utilization of the Pd catalyst with high TONs (turnover numbers) and further decreases the loadings of metal species and alkali. This state transformation of the catalyst not only endows the Pd(II) species with high catalytic activity and stability, but also offers new insights into the catalytic behavior of heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

The emerging semiconductor boron arsenide (BAs) with high thermal conductivity has attracted much attention recently, due to its promising application to overcome the bottleneck of high-density heat generated in power electronics and optoelectronic devices. In this work, based on first-principles calculations, we find that cubic BAs possesses high intrinsic electron/hole mobilities and the ionized impurity scattering plays a more important role in carrier scattering, compared with other scattering processes. The mobilities can be significantly enhanced by 14.9% and 76.2% for electrons and holes, respectively, by strain engineering. The investigation of the optoelectronic properties of indirect semiconductor cubic BAs by considering the many-body excitonic effects reveals that the contribution from finite-momentum excitons to optical properties is larger for photon energy ranging from 2.25 eV to 3.50 eV, compared with that from zero-momentum excitons. Finally, we observe that the phonon–electron couplings to total lattice thermal conductivities are non-trivial at low temperatures. These findings provide new insight into the transport and optoelectronic properties of cubic BAs, which are beneficial for the acceleration of the application of this revolutionary thermal management material. [ABSTRACT FROM AUTHOR]