Lignin Based Molecular Materials – a Zinc Vanillate with a Hydrogen Bonded 4‐ and 8‐connected Net with a New Topology

Abstract

Vanillic acid, C 8 H 8 O 4 , is a possible product from a future biorefinery with lignin as raw material. Two coordination compounds with this ligand in two different protonation states were prepared: 1 [Zn(C 8 H 7 O 4 ) 2 (H 2 O) 2 ] and 2 [Co 2 (C 8 H 6 O 4 ) 2 (H 2 O) 6 ] · 2H 2 O. Both compounds form extended 3Dstructures with strong hydrogen bonds. A high symmetry 8and 4-connected network topology, jus, is found in 1. The dinuclear coordination entity in 2 hints at a potentially useful SBU for MOF synthesis from lignin based bridging ligands.

Lignin and metal–organic frameworks: mutual partners on the road to sustainability

“…In addition, the oxygen atom of the water molecule and the deprotonated carboxylic acid of vanillic acid coordinated with Zn to form a network topology centered on Zn. 13 Similarly, the coordination of vanillic acid with Co led to the synthesis of the binuclear compound [Co 2 (C 8 H 6 O 4 ) 2 ]$2H 2 O (Fig. 5b and c).…”

“…5a. This network uses only two types of hydrogen bonds, i.e., one is the O5-H6/O4 between the ligand water and phenol groups 13 and the other is the O4-H3/O2 bond between the phenol proton and the unliganded carboxylic acid oxygen atom using charge assistance. In addition, the oxygen atom of the water molecule and the deprotonated carboxylic acid of vanillic acid coordinated with Zn to form a network topology centered on Zn.…”

“…5b and c). 13 Curiously, with vanillic acid deprotonated at both ends and Co coordinated only to the methoxy and phenoxy ends, the compound is held together only by hydrogen bonds, with the free water and the hydrogen bonds between the ligand water and the carboxylate forming a dense two-dimensional network.…”

“…2), as derivatives of lignin, are degraded from lignin and can all be used as ligands for the synthesis of MOFs. 11,13,18,19 This is not only expected to solve the challenges faced by MOFs in terms of biocompatibility, but also contribute to the high-end application of lignin.…”

“…12 Based on the inevitability of the transition from fossil chemistry to biochemistry, it is important to find sustainable target substances to replace starting materials for the chemical industry. 13 Therefore, for the application of MOFs, it is urgent to find bio-based alternatives to chemical substances. Fortunately, the common ligands for the synthesis of MOFs are aromatic multi-layer carboxylic acids, which are available from biomass.…”