Reversible CO 2 Fixation and Release by a Trinuclear Zn(II) Cryptate Complex and Operando Analysis of the Complex Structure

• Published in: ChemSusChem Vol. 16; no. 20
• Main Authors: Murase, Masakazu, Maegawa, Yoshifumi, Ohashi, Masataka, Goto, Yasutomo, Sakamoto, Naonari, Nonaka, Takamasa, Uyama, Takeshi, Arai, Takeo
• Format: Journal Article
• Language: English
• Published: 20.10.2023
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.202300679

Abstract Metal complexes inspired by carbonic anhydrase (CA), which is a metalloenzyme containing Zn(II), have been investigated as alternatives for CO 2 fixation systems operating under ambient temperature and pressure conditions. In this study, we designed a trinuclear Zn(II) cryptate complex (Zn 3 L) and demonstrated rapid CO 2 fixation with carbonation of CO 2 using Zn 3 L. The CO 2 fixation performance of Zn 3 L surpassed that of a standard CO 2 absorbent, KOH(aq) solution, under conditions of the same solute concentration. In addition, the reaction achieved operation without support addition of base, which has been often required in systems of CA‐inspired complexes. Fixed CO 2 was released by protonating polyazacryptate ligand (L) and breaking the complex structure, and deprotonation of L induced the reconstruction of Zn 3 L, allowing it to refix CO 2 . This reaction mechanism was proposed based on the analysis of operando extended X‐ray absorption fine structure spectroscopy. Zn 3 L also demonstrated the ability to capture dilute CO 2 from air, and the volume of CO 2 captured by Zn 3 L was approximately 2.6 times that captured by the KOH(aq) solution. Our Zn 3 L exhibited three valuable properties: rapid CO 2 fixation without a base, reversibility, and ability to capture dilute CO 2 ; thus Zn 3 L is a promising candidate as CO 2 fixatives.