3次元多孔性材料が切り拓く新技術～水質汚染の原因となる硝酸からグリーン燃料を合成～

2026-02-06 東北大学

図1. 3次元共有結合性有機構造体（COF）TU-82を用いた、電気化学的硝酸イオン還元反応（eNO₃^–RR）によるアンモニア（NH₃）合成の概念図。農業排水や工業排水中の主要な汚染物質である硝酸イオン（NO₃⁻）が、3次元COF TU-82の骨格内に組み込まれた金属-ビピリジン触媒活性点を介して、常温・常圧条件下で付加価値の高いNH₃へと変換される様子を示している。

＜関連情報＞

• https://www.tohoku.ac.jp/japanese/2026/02/press20260206-02-3D.html
• https://www.tohoku.ac.jp/japanese/newimg/pressimg/tohokuuniv-press20260206_02web_.pdf
• https://pubs.rsc.org/en/content/articlelanding/2026/ta/d5ta07989f

[8 + 2]結合した三次元金属-ビピリジン共有結合有機骨格上での電気触媒硝酸塩還元 による 効率的なアンモニア合成 Efficient ammonia synthesis via electrocatalytic nitrate reduction over a [8 + 2]-connected three-dimensional metal-bipyridine covalent organic framework

Tsukasa Irie,Ayumu Kondo,Kai Sun,Kohki Sasaki,Mika Nozaki,Shiho Tomihari,Kotaro Sato,Tokuhisa Kawawaki,Yu Zhao,Saikat Das and Yuichi Negishi
Journal of Materials Chemistry A  Published:02 Feb 2026
DOI:https://doi.org/10.1039/D5TA07989F

Abstract

Covalent organic frameworks (COFs) have recently emerged as promising platforms for electrocatalytic nitrate reduction to ammonia (NO₃RR), yet most reported systems are limited to two-dimensional architectures. Herein, we present TU-82, a structurally distinct 3D COF featuring an intricate [8 + 2]-connected bcu topology derived from the reticulation of an octatopic D_2h-symmetric tetragonal prism node and a C₂-symmetric bipyridyl linker. TU-82 exhibits high crystallinity, permanent porosity, and robust structural integrity, enabling precise postsynthetic metalation at bipyridyl coordination sites to yield catalytically active TU-82-Fe and TU-82-Cu frameworks. Among them, TU-82-Fe demonstrates superior NO₃RR performance, delivering a faradaic efficiency (FE) of 88.1% at −0.6 V (RHE) and an ammonia yield rate of 2.87 mg h⁻¹ cm⁻² at −0.8 V (RHE), together with a turnover frequency of 7.2 h⁻¹ and excellent operational stability. Density functional theory calculations reveal that the enhanced activity of TU-82-Fe originates from a lower energy barrier (0.354 eV) for the rate-determining NO* → NHO* step along the NHO-mediated reaction pathway. This work pioneers a structural blueprint for deploying 3D COFs in electrocatalysis, fostering deeper insights into framework-controlled reactivity and offering new routes to sustainable nitrate management.