Trinuclear Cd3O14 hexaborate and two nickel borates based on molten salt synthesis and precursor synthesis: structure, characterization, and properties.

In this work, different synthetic methods were used to prepare metal borates. One cadmium borate Cd3[B6O9(OH)2]2·2NO3·4H2O (1) and two nickel borate Ni0.8Mn0.2{B6O7(OH)3[O(CH2)2NH2]3} (2), [Ni(1-MI)6]·[B5O6(OH)4]2·2DMF (3, 1-MI = 1-methylimidazole, DMF = N,N-dimethylformamide) species were successfully prepared. The structures of these three compounds were confirmed via single crystal powder X-ray diffraction (SCPXRD), elemental analysis, FTIR, PXRD, and ICP studies. Compound 1 was prepared via molten salt synthesis, and compounds 2 and 3 were prepared via precursor synthesis, which is a synthetic method that uses a certain polyanionic cluster as a reagent. Compound 1 shows a novel three-dimensional (3D) structure, in which the [B6O11(OH)2] units acting as the basic polyanionic cluster form a two-dimensional (2D) anionic structure. In addition, the unexpected Cd3O14 clusters are connected with the 2D structures, leading to the 3D structure. The crystal structure of 2 is packed with very large neutral Ni0.8Mn0.2{B6O7(OH)3[O(CH2)2NH2]3} oxo-metal-boron clusters. The crystal structure of 3 consists of a [B5O6(OH)4]- cluster, a DMF molecule, and a [Ni(1-MI)6]2+ complex. In particular, 2 was successfully constructed using the same hexaborate cluster as its precursor. However, 3 only contains Ni2+ cations when a neutral NixMn1-x[B6O7(OH)6] cluster was used as an initial reagent, and it shows an ability to select a certain metal cation during the self-assembly process. Moreover, compounds 1, 2, and 3 exhibit different wide band gaps of 3.06 eV (1), 3.95 eV (2), and 4.24 eV (3).

Regulating the Coordination Environment of MOF-Templated Single-Atom Nickel Electrocatalysts for Boosting CO2 Reduction.

The general synthesis and control of the coordination environment of single-atom catalysts (SACs) remains a great challenge. Herein, a general host-guest cooperative protection strategy has been developed to construct SACs by introducing polypyrrole (PPy) into a bimetallic metal-organic framework. As an example, the introduction of Mg2+ in MgNi-MOF-74 extends the distance between adjacent Ni atoms; the PPy guests serve as N source to stabilize the isolated Ni atoms during pyrolysis. As a result, a series of single-atom Ni catalysts (named NiSA -Nx -C) with different N coordination numbers have been fabricated by controlling the pyrolysis temperature. Significantly, the NiSA -N2 -C catalyst, with the lowest N coordination number, achieves high CO Faradaic efficiency (98 %) and turnover frequency (1622 h-1 ), far superior to those of NiSA -N3 -C and NiSA -N4 -C, in electrocatalytic CO2 reduction. Theoretical calculations reveal that the low N coordination number of single-atom Ni sites in NiSA -N2 -C is favorable to the formation of COOH* intermediate and thus accounts for its superior activity.

Formation Mechanism of a Polyanonic Framework from Layer to Chain Explored by Adjusting Time, Temperature, and pH: Preparation and Characterization of Metal-Complex-Templated 1D Borate and 2D Nickel Borate.

The first column of two-dimensional (2D)-layered metal-complex-templated nickel borate was obtained by using a solvothermal synthesis method. The 2D nickel borate [Ni(en)3]·[Ni0.5B6O8(OH)4]·Cl (1; en = ethylenediamine) contains [Ni(en)3]2+, Cl-, and the first reported inorganic nickel borate layer [Ni0.5B6O8(OH)4]-, which is formed by the interconnection of Ni and O atoms in the B-O cluster. By increasing the reaction temperature during the synthesis process of compound 1, the one-dimensional (1D) chain nickel borate [Ni(en)3]2·[B7O10(OH)3]·Cl2 (2) was obtained, wherein the [B7O10(OH)3] cluster was connected through an O atom to form a 1D chain structure. By adjusting the molar ratio of the raw materials, that is, adjusting the pH of the reaction, the other 1D chain nickel borate Ni(en)3·Hen·[B9O13(OH)4]·H2O (3) was obtained, in which [B5O8(OH)2] and [B4O7(OH)2] clusters can be connected via a common O atom to form an infinite [B9O13(OH)4] polyanionic chain. Meanwhile, we successfully synthesized the isoform of compound 3 with the metal cadmium.

Photoluminescent carbon dots based on a rare 3D inorganic-organic hybrid cadmium borate crystal.

A 3D inorganic-organic hybridized skeleton cadmium borate [Cden][B5O8(OH)] (1) (en = ethylenediamine) has been solvothermally synthesized. By calcining it, specific shape carbon dots (C-dots) with abundant free radicals were observed. In addition, C-dots in the ethanol phase exhibited variable photoluminescence and showed rare turn on or off effects to Cr3+ ions and CdSe/ZnS quantum dots, but only a turn on effect to Cs+ ions and a turn off effect to CsPbBr3 quantum dots.

Bright violet-to-aqua-emitting cadmium-free Ag-doped Zn-Ga-S quantum dots with high stability.

Herein, we report a new series of ultra-stable Cd-free Ag:Zn-Ga-S/ZnS quantum dots (QDs) with an overall short emission wavelength tunable from 370 to 540 nm via a facile one-pot non-injection method. The highest PL quantum yield of the resultant core/shell QDs could be up to 85%, and the exceptional luminescence could be maintained not only at 300 °C but also after phase transfer.

Unprecedented Li+ Exchange in an Anionic Metal-Organic Framework: Significantly Enhanced Gas Uptake Capacity.

We herein report the first example of Li+ exchanged with both the guest H2N(Me)2+ cations located in the channels and the coordinated metal ions from an anionic metal-organic framework (MOF), leading to significant enhancement of the pore volume and gas sorption abilities of the exchanged MOF. Furthermore, both MOFs before and after Li+ exchange show good selective adsorption for CO2 over CH4.