Vibrational Properties of Boroxine Anhydride and Boronate Ester Materials: Model Systems for the Diagnostic Characterization of Covalent Organic Frameworks

Abstract

The vibrational characteristics of 28 different boronic acid, boroxine anhydride, and boronate ester species have been systematically investigated using a combination of experimental infrared (IR) spectroscopy and computational modeling. IR bands characteristic to each boron-containing functionality have been categorized and assigned in conjunction with density functional theory (B3LYP/6-31G­(d)), with the aim of better understanding and distinguishing the vibrational characteristics of covalent organic frameworks (COFs) built from boronic acids. In several cases, vibrational assignments differ from those previously reported in the literature on boronic acid-based COFs. Vibrations commonly regarded as diagnostic for one functionality are found in regions of the IR spectrum where other functionalities also show characteristic peaks. The collective experimental and computational results reveal that several alternative bands in the IR region can be used to more diagnostically distinguish between boronic acid, boroxine anhydride, and boronate ester species. The results presented herein provide the tools for straightforward characterization of boroxine anhydride and boronate ester species using IR spectroscopy. The results can be applied to additional theoretical studies of larger COF-like assemblies as well as the analysis of other boronic-acid-based materials.

Two‐Dimensional Boronate Ester Covalent Organic Framework Thin Films with Large Single Crystalline Domains for a Neuromorphic Memory Device

“…The formation of boronate ester bonds (C 2 O 2 B ring) in the 2D BECOF‐PP was confirmed by FT‐IR spectroscopy with the appearance of vibrational C−O bonds at 1122 cm −1 (Figure b) . Additionally, the strong peak at 1339 cm −1 displays the band corresponding to the B−O stretch within the C 2 O 2 B ring.…”

Extraction of Photogenerated Electrons and Holes from a Covalent Organic Framework Integrated Heterojunction

“…This was also confirmed by quenched-solid density functional theory (QSDFT) calculations, which showed an average pore diameter of 4.6 nm (Figure 2 f). The calculated Brunauer–Emmett–Teller (BET) surface area is 890 m 2 g –1 , with a pore volume of 1.1 cm 3 g –1 (for further characterization of the material, 33 see section 6 in the SI ).…”

Expanded Porous Metal–Organic Frameworks by SCSC: Organic Building Units Modifying and Enhanced Gas-Adsorption Properties

“…52,53 The adsorption capacities for H 2 are 131.38 and 91.08 cm 3 ·g −1 at 77 and 87 K, respectively (Figure 3b and Table 2), which is larger than UTSA-36 with a similar BET surface area 54 of 806 m 2 ·g −1 and a H 2 adsorption capacity of 123.00 cm 3 ·g −1 (1.1 wt %) at 77 K. 55 The adsorption capacities for CO 2 , C 2 H 2 , and CH 4 are 85.92, 87.50, and 22.79 cm 3 ·g −1 at 273 K, whereas CO 2 at 298 K is 49.63 cm 3 ·g −1 .…”