Hexane-1,2,5,6-tetrol as a Versatile and Biobased Building Block for the Synthesis of Sustainable (Chiral) Crystalline Mesoporous Polyboronates

Mario De Bruyn; Paolo Cuello-Penaloza; Melissa Cendejas; Ive Hermans; Jiayue He; Siddarth H Krishna; David M Lynn; James A Dumesic; George W Huber; Bert M Weckhuysen

doi:10.1021/acssuschemeng.9b02772

Hexane-1,2,5,6-tetrol as a Versatile and Biobased Building Block for the Synthesis of Sustainable (Chiral) Crystalline Mesoporous Polyboronates

ACS Sustain Chem Eng. 2019 Aug 5;7(15):13430-13436. doi: 10.1021/acssuschemeng.9b02772. Epub 2019 Jul 3.

Authors

Affiliations

¹ Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, Wisconsin 53706, United States.
² Faculty of Science, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands.
³ Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States.

Abstract

We report on the synthesis and characterization of novel mesoporous chiral polyboronates obtained by condensation of (R,S)/(S,S)-hexane-1,2,5,6-tetrol (HT) with simple aromatic diboronic acids (e.g., 1,3-benzenediboronic acid) (BDB). HT is a cellulose-derived building block comprising two 1,2-diol structures linked by a flexible ethane bridge. It typically consists of two diastereomers one of which [(S,R)-HT] can be made chirally pure. Boronic acids are abundantly available due to their importance in Suzuki-Miyaura coupling reactions. They are generally considered nontoxic and easy to synthesize. Reactive dissolution of generally sparingly soluble HT with BDB, in only a small amount of solvent, yields the mesoporous HT/polyboronate materials by spontaneous precipitation from the reaction mixture. The 3D nature of HT/polyboronate materials results from the entanglement of individual 1D polymeric chains. The obtained BET surface areas (SAs) and pore volumes (PVs) depend strongly on HT's diastereomeric excess and the meta/para orientation of the boronic acids on the phenyl ring. This suggests a strong influence of the curvature(s) of the 1D polymeric chains on the final materials' properties. Maximum SA and PV values are respectively 90 m² g^-1 and 0.44 mL g^-1. Variably sized mesopores, spanning mainly the 5-50 nm range, are evidenced. The obtained pore volumes rival the ones of some covalent organic frameworks (COFs), yet they are obtained in a less expensive and more benign fashion. Moreover, currently no COFs have been reported with pore diameters in excess of 5 nm. In addition, chiral boron-based COFs have presently not been reported. Scanning electron microscopy reveals the presence of micrometer-sized particles, consisting of aggregates of plates, forming channels and cell-like structures. X-ray diffraction shows the crystalline nature of the material, which depends on the nature of the aromatic diboronic acids and, in the specific case of 1,4-benzenediboronic acid, also on the applied diastereomeric excess in HT.