Understanding the Role of Titanium Metal-Organic Framework Nanosheets in Modulating Anode Chemistry for Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries have attracted a continually increasing level of interest for large-scale energy storage because they are highly safe and have high energy density and abundant reserves. However, Zn anodes face significant challenges such as severe dendrite growth and hydrogen evolution reaction (HER). We here propose an efficient Zn2+ sieve strategy for modulating the anode chemistry using two-dimensional NH2-MIL-125 (Ti) metal-organic framework (MOF) nanosheets. Theoretical investigations reveal the crucial role of the Ti MOF in regulating Zn2+ solvation structures for fast diffusion and uniform deposition and decreasing HER reactivity. The structure of the nanosheets enables abundant accessible desolvation sites and shortened ionic pathways. As a result, the MOF nanosheet-protected Zn anode exhibited greatly improved cycling stability in both symmetric cells and full cells. Operando optical monitoring and postmortem analysis revealed effective suppression of dendrite growth and HER by Ti MOF nanosheets. This anti-HER MOF-enabled Zn2+ sieve strategy provides a viable Zn anode and provides new insights for optimizing aqueous batteries.

Modulating the Chemical Microenvironment of Pt Nanoparticles within Ultrathin Nanosheets of Isoreticular MOFs for Enhanced Catalytic Activity.

The catalytic activity of metal nanoparticles (MNPs) embedded in metal-organic frameworks (MOFs) is affected by the electronic interactions between MNPs and MOFs. In this report, we fabricate a series of ultrathin nanosheets of isoreticular MOFs (NMOFs) with different metal nodes as supports and successfully encapsulate Pt NPs within these NMOFs, affording Pt@NMOF-Co, Pt@NMOF-Ni1Co1, Pt@NMOF-Ni3Co1, and Pt@NMOF-Ni nanocomposites. The microchemical environment on the surface of Pt NPs can be modulated by varying the metal nodes of NMOFs. The catalytic activity of the nanocomposites toward liquid-phase hydrogenation of 1-hexene shows obvious difference, in which Pt@NMOF-Ni possesses the highest activity followed by Pt@NMOF-Ni3Co1, Pt@NMOF-Ni1Co1, and Pt@NMOF-Co in a decreasing order of activity. Obviously, increasing gradually the amount of Ni2+ nodes in the carriers can improve the catalytic activity. The difference of catalytic activity of the nanocomposites might originate from the distinct electron interactions between Pt NPs and NMOFs, as ascertained by X-ray photoelectron spectroscopy spectrum and density functional theory calculations. This work provides a rare example that the catalytic activity of MNPs could be controlled by accurately regulating the microchemical environment using ultrathin NMOFs as supports.

Engineering Two-Dimensional Metal-Organic Framework on Molecular Basis for Fast Li+ Conduction.

Metal-organic frameworks (MOFs) have been proposed as emerging fillers for composite polymer electrolytes (CPEs). However, MOF particles are usually served as passive fillers that yield limited ionic conductivity improvement. Building continuous MOF reinforcements and exploiting their active roles remain challenging. Here we demonstrate the feasibility of engineering fast Li+ conduction within MOF on molecule conception. Two-dimensional Cu(BDC) MOF is selected as an active filler due to its sufficient accessible open metal sites for perchlorate anion anchoring to release free Li+, verified by theoretical calculations and measurements. A novel Cu(BDC)-scaffold-reinforced CPE is developed via in situ growth of MOF, which provides fast Li+ channels inside MOF and continuous Li+ paths along the MOF/polymer interface for high Li+ conductivity (ambient 0.24 mS cm-1) and enables high mechanical strength. Stable cycling is achieved in solid-state Li-NCM811 full cell using the MOF-reinforced CPE. This molecule-basis Li+ conduction strategy brings new ideas for designing advanced CPEs.

Embedded homogeneous ultra-fine Pd nanoparticles within MOF ultra-thin nanosheets for heterogeneous catalysis.

Metal nanoparticle-incorporated metal-organic framework (MOF) nanosheets can integrate their respective merits to have important applications in heterogeneous catalysis. Herein, we report the loading of ultra-fine Pd nanoparticles within ultra-thin nanosheets NMOF-Ni through an in situ reduction strategy under mild conditions. Owing to the synergetic effects of ultra-small Pd NPs and the intrinsic characteristics of two-dimensional supports, the obtained Pd@NMOF-Ni showed high catalytic activity and size-selectivity in olefin hydrogenation with easy recovery. Meanwhile, Pd@NMOF-Ni is also highly active in the catalytic reduction of aqueous 4-nitrophenol to 4-aminophenol.

In Situ Tuning of Defects and Phase Transition in Titanium Dioxide by Lithiothermic Reduction.

Defects engineering of oxides plays a vital role in tuning their physicochemical and electronic properties and thereby determining their potential applications. However, the safe and controllable production of effective defects in the oxides is still challenging. Here, we report a facile one-pot solid lithiothermic reduction approach to generate graded oxygen defects in TiO2 nanoparticles. Various levels of lithium reduction are systematically studied, and meanwhile, a distinct phase transition from anatase TiO2 to cubic LixTiO2 is observed with the increasing lithium ratio. The structure and evolution of surface defects and bulk phase transition are investigated in detail. Afterward, we demonstrate their applications in carbon dioxide photoreduction and photothermal imaging. The slightly reduced TiO2 with effective oxygen defects affords a highly broadened solar spectrum absorption and yields significantly enhanced visible photocatalytic activity in CO2 conversion, which is further revealed by theoretical calculations. The highly reduced TiO2 with obvious phase transition shows enhanced solar absorption and achieves high photo-thermal-conversion efficacy, showing huge potential in photo-thermal-related applications. The lithiothermic reduction is a general and effective approach to produce defects and induce phase transition in oxides, which can be used in multiple applications.

Synthesis, structure and urease inhibition studies of Schiff base copper(II) complexes with planar four-coordinate copper(II) centers.

Seven new Schiff base copper(II) complexes with planar four-coordinate copper(II) centers have been synthesized and structurally characterized. The solid state structures of complexes 1, 3, 4, 5, 6 and 7 present a square-planar coordination geometry at the metal centers while complex 2 shows a slightly distorted square-planar geometry. Density functional theory calculations have been performed to evaluate the electronic structure of copper(II) complex 7. Inhibition of jack bean urease by copper(II) complexes 1-7 have also been investigated, and potent inhibitory activities with IC50 range of 2.60-17.00µM have been observed for these mononuclear copper(II) complexes. A docking analysis using a DOCK program was conducted to explain the urease inhibitory activity of the copper(II) complexes and the structure-activity relationships were further discussed.