Fluorination Strategy Towards Symmetry Breaking of Boron-centered Tetrahedron for Poly-fluorinated Optical Crystals.

Borate crystals can be chemically and functionally modified by the fluorination strategy, which encourages the identification of emerging fluorooxoborates with a structure and set of characteristics not seen in any other oxide parents. However, the bulk of fluorooxoborates have been found accidentally, rational methods of synthesis are required, particularly for the infrequently occurring poly-fluorinated components. Herein, we reported the use of bifluoride salts as a potent source of fluorine to prepare fluorooxoborates that contain rarely tri-fluorinated [BF3 X] (X=O and CH3 ) tetrahedra and eleven compounds were found. We identified the optical properties of the organofluorinated group [CH3 BF3 ] and their potential for nonlinear optics for the first time. Among these, two non-centrosymmetric components hold potential for the production of 266 nm harmonic coherent light for nonlinear optics, and more crucially, have the benefit of growing large size single crystals. Our study establishes experimental conditions for the coexistence of the diverse functional groups, enabling the production of poly-fluorinated optical crystals.

Breaking the Inherent Interarrangement of [B3O6] Clusters for Nonlinear Optics with Orbital Hybridization Enhancement.

The [B3O6] group as a prime functional unit provides borates with intrinsic properties that are modified by coordination to cations. Inherent [B3O6] cluster structures in borates exclusively made of them have a near-plane configuration, with more than 90% of them having a maximum dihedral angle of zero and the remaining ones being less than 13°. Although such an inherent configuration can produce considerable birefringence for good phase-matching ability, this is not conducive to obtaining high conversion efficiency and beam quality due to the walk-off effects in the nonlinear optical process. In this article, two new borate halides Ca2B3O6X (X = Cl and Br) were reported, in which the confinement effects of distorted halogen-centered secondary building blocks compress the existence space of [B3O6] primitives, resulting in the nonparallel arrangement between [B3O6] clusters in this series. Both compounds show large second harmonic generation effects, and more importantly, the broken inherent interarrangement of [B3O6] clusters makes them a moderate birefringence and small walk-off angle. Their moderate birefringence is due to the large angular alignment between [B3O6] clusters, resulting from the orbital hybridization between the Ca s and the O p orbitals of the terminal O atoms on [B3O6] clusters. Our model supports this viewpoint and offers guidelines for rearranging [B3O6] clusters' arrangements in borates.

Double-Modification Oriented Design of a Deep-UV Birefringent Crystal Functionalized by [B12 O16 F4 (OH)4 ] Clusters.

Polarization modulation of deep-UV light is of significance to current technologies, and to this end, the birefringent crystal has emerged as an invaluable material as it allows for effective light modulation. Herein, a double-modification strategy driven by F and OH anions that makes double effects towards the critical property enhancement of deep-UV birefringent crystals is proposed. This leads to a new hydroxyborate (NH4 )4 [B12 O16 F4 (OH)4 ] with giant cluster as a deep-UV birefringent crystal with large birefringence (Δnexp. =0.12@546.1 nm). This birefringence is a record among inorganic hydroxyborates with experimentally measured birefringence. Structural analysis shows that the near-plane arrangement of [B12 O16 F4 (OH)4 ] cluster is responsible for the large optical anisotropy. Theoretical calculations indicate that its π-conjugated [BO3 ] and [BO2 OH] units are the main source of this large optical anisotropy.

LiCs3AlB7O14: achieving enhanced optical anisotropy via [AlO4] tetrahedron introduction to rearrange the anionic framework.

Borate has become a hot topic because of its rich structural chemistry and excellent properties for functional materials fields. The rearrangement of π-conjugated B-O units is key to enhancing the optical anisotropy, but it remains a challenge. Herein, by introducing [AlO4] tetrahedra, a new congruent melting aluminoborate LiCs3AlB7O14 with [B7O14] clusters was discovered. This work confirms that the introduction of [AlO4] tetrahedra can lead to the rearrangement of anionic framework of the borate system and thereby enhance the birefringence of LiCs3AlB7O14. The birefringence is about 4.1 times higher than that of its congener Li4Cs3B7O14 with the same [B7O14] clusters. Similarly, the effects of [AlO4] tetrahedra on the rearrangement of the B-O anionic framework are also demonstrated in other known borates.

(N2H6)[HPO3F]2: maximizing the optical anisotropy of deep-ultraviolet fluorophosphates.

Although phosphates are a rich source of deep-ultraviolet optical materials, the realization of large optical anisotropy in them still remains a challenge because of the small polarizability anisotropy of [PO4] units. Inspired by the fluoridation strategy and hydrogen bond interaction, a new metal-free monofluorophosphate, (N2H6)[HPO3F]2, was synthesized, which exhibits a large birefringence (cal. 0.077) and wide band gap (∼6.51 eV). Such a large birefringence in (N2H6)[HPO3F]2 sets a new record among available fluorophosphates, and the [HPO3F] unit is theoretically confirmed to be a new birefringence-active unit.

Tetrafluoroborate-Monofluorophosphate (NH4)3[PO3F][BF4]: First Member of Oxyfluoride with B-F and P-F Bonds.

Inspired by the strategy of fluorine introduction in borates and phosphates, the inorganic oxyfluoride (NH4)3[PO3F][BF4] with B-F and P-F bonds has been characterized as the first fluoroborate-fluorophosphate. The International Union of Pure and Applied Chemistry (IUPAC) name for (NH4)3[PO3F][BF4] should be ammonium tetrafluoroborate-monofluorophosphate according to the structure characteristics. The existence and coordination of fluorine in (NH4)3[PO3F][BF4] were confirmed by several approaches, including single-crystal structure analysis; bond valence analysis; and X-ray energy dispersive, infrared spectrum, and also nuclear magnetic resonance spectroscopy. This work is of great significance to enrich the solid-state chemistry of borates and phosphates and also open a new branch of mixed anion compound with fluoroborate-fluorophosphates.

BaZn3(BO3)2F2: a new beryllium-free zincoborate with a KBBF-type structure.

A new beryllium-free zincoborate, BaZn3(BO3)2F2, with a KBBF-type structure has been synthesized for the first time. The electrostatic force of interaction in BaZn3(BO3)2F2 provides better linkage in neighboring [ZnBO3F]∞ single layers. BaZn3(BO3)2F2 is the first case of borates with both [ZnO3F] tetrahedra and [ZnO6] octahedra, enriching the structural chemistry of borate system. All the coplanar [BO3] triangles align in the same direction with a high density, which endows BaZn3(BO3)2F2 with a large birefringence of cal. 0.076 at 1064 nm. This work is of great significance to design beryllium-free borates with a KBBF-type structure.

[Synthesis and application of a surface molecularly imprinted adsorbent for di(2-ethylhexyl)phthalate base on graphite oxide].

A molecularly imprinted polymer (MIP) base on the surface of graphite oxide (GO) has been developed for the selective recognition of di(2-ethylhexyl)phthalate (DEHP), and applied for the extraction of DEHP in a milk bag sample, with detection by high-performance liquid chromatography. The surface-molecularly imprinted material was prepared by precipitation polymerization in N,N-dimethylformamide (DMF) solvent, using GO as the supporting material, DEHP as the template molecule, and methacrylic acid (MAA) as the functional monomer; the synthesis conditions were also optimized. The obtained GO-MAA-MIP was characterized by Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM). The adsorption properties of the product were evaluated by adsorption experiments, including adsorption isotherms, kinetics, selectivity, saturated adsorption capacity, adsorption equilibrium time, and reusability. Under optimized conditions, DEHP was effectively extracted in the real sample (milk bag) and detected by HPLC. Linearity was obtained with a correlation coefficient (R2) of 0.9979 in a linear range of 0.5-50 mg/L. The limits of detection and quantitation were 0.03 mg/L and 0.1 mg/L, respectively. The average recoveries of the spiked samples at three concentration levels of DEHP ranged from 81.6% to 92.4% with relative standard deviations (RSDs) less than 7%. The results indicated that the proposed GO-MAA-MIP-SPE (solid phase extraction) protocol with HPLC-UV detection could be applied for the selective analysis of DEHP in real samples.