Outerly functionalized and non-functionalized boron clusters intercalated into layered hydroxides with different modes of binding: materials for superacid storage

Abstract

Two binary boron hydrides (NH4)2B10H10 and Na2B12H12 and mono- and dicarboxy p- and m-carboranes (namely, 1-(COOH)-closo-1,7-C2B10H11, 1,12-(COOH)2-closo-1,12-C2B10H10 and 1,7-(COOH)2-closo-1,7-C2B10H10) were intercalated into ZnAl-layered double hydroxides (ZnAl-LDH) and into Zn5(OH)8(NO3)2·2H2O. The formed compounds were characterized using elemental analysis, thermogravimetry analysis, X-ray powder diffraction, infrared spectroscopy and solid state NMR. All the intercalated boron compounds are present in the interlayer space of the layered hosts as anions. It is presumed that in the case of B10H102-, B12H122- and 1,12-(COO)2-closo-1,12-C2B10H102-, the guest molecules form a monolayer, whereas in the case of 1-(COO)-closo-1,7-C2B10H111- and 1,7-(COO)2-closo-1,7-C2B10H102- a bilayer arrangement is more probable. In the case of 1,7-(COO)2-closo-1,7-C2B10H102-, the guest molecules are strongly interdigitated resulting in lowering of the interlayer distance. Two different modes of binding were found. Whereas the carboxylate derivatives of p- and m-carboranes are bonded through classical hydrogen bonds, the corresponding parent borane anions interact with the host structures by mainly dihydrogen bonding. In effect, both kinds of hydrogen bonding are mainly of an electrostatic nature. The dihydrogen bond is detected, e.g. in crystal engineering, and represents a driving force for interactions of boranes with biomolecules. Since the latter dicarboxylic acids were found to be superacids, their interactions with the host structures should be stronger than in the case of the benzoic and terephthalic acid intercalates.

Solid state NMR studies of layered double hydroxides

“…11 B single-pulse and 3QMAS NMR probed the changes in speciation of inorganic borates in ZnAl-LDH as a function of time based on the characteristic δiso( 11 B) line shapes for the different species, as variable temperature 11 B MAS NMR spectra showed a dynamic exchange between trigonal and tetrahedral boron species [103]. Similarly, 11 B MAS NMR gave insight into the structure of carboranes intercalated in ZnAl-LDH [115].…”

Structural Characterization of Boron Sheets beyond the Monolayer and Implication for Experimental Synthesis and Identification

“…Borophene, a novel 2D material with rich polymorphism and anisotropic metallic behavior, holds great promise for energy storage of ion batteries, − lithium–sulfur batteries, − and energy conversion of electrochemical catalysis, − and the performance is comparable to other common 2D materials. , The successful synthesis of monolayer borophene and the identification of atomic structures in experiments are inseparable from the above characterization methods. ,, After that, boron sheets beyond monolayer with higher stability and superior antioxidation are predicted in theory, which can be attributed to the formation of pillars and strong coupling strength between interlayers. − In addition, 3D-boron clusters intercalated into layered hydroxides could be utilized in superacid storage and dynamical disordering in MgB 2 materials in hydrogen storage performance . It is worth noting that recent experiments successfully fabricated quasi-freestanding bilayer borophene on Ag(111) and Cu(111) surfaces, and the metallicity is preserved. , In addition, the vibrational modes of bilayer borophene on the Ag(111) substrate found coupling interactions between boron sheets and substrate in visible and IR regions, and the strongest vibration occurred at the interlayer chemical bonds of boron atoms, further proposing the huge potential in optoelectronic devices.…”

“…7,35,36 After that, boron sheets beyond monolayer with higher stability and superior antioxidation are predicted in theory, which can be attributed to the formation of pillars and strong coupling strength between interlayers. 37−40 In addition, 3Dboron clusters intercalated into layered hydroxides could be utilized in superacid storage 41 and dynamical disordering in MgB 2 materials in hydrogen storage performance. 42 It is worth noting that recent experiments successfully fabricated quasifreestanding bilayer borophene on Ag(111) and Cu(111) surfaces, and the metallicity is preserved.…”

Benchmark Data Sets of Boron Cluster Dihydrogen Bonding for the Validation of Approximate Computational Methods

“…[30] Consequently, the most characteristic noncovalent interaction of boron hydrides is a dihydrogen bond, [16] a nonclassical hydrogen bond of EÀ H•••HÀ B type (E, a more electronegative element than hydrogen, e. g. O, N). [31] Via dihydrogen bonds, heteroboron clusters bind to (in)organic compounds including self-association [20,23,32,33] and biomolecules, such as inhibitors of HIV protease (PR) [16,34] or carbonic anhydrase. [35][36][37] This paper addresses the lack of parameterization and validation approaches for approximate computational methods utilized for boron compounds.…”