「光を当てすぎない」ことが⾼効率CO2変換の鍵だった −分⼦／半導体ハイブリッド光触媒の新たな設計指針を確⽴−

2026-03-25 東京科学大学

図1. ルテニウム錯体分子／銀ナノ粒子担持窒化炭素ハイブリッド光触媒によるCO₂還元のイメージ図

＜関連情報＞

• https://www.isct.ac.jp/ja/news/h9nwhqiroy9k
• https://pubs.acs.org/doi/10.1021/jacs.5c21374

可視光CO2還元用Ru錯体/Ag/高分子窒化炭素ハイブリッド光触媒における隠れた限界の起源の解明 Elucidating the Origin of Hidden Limitations in Ru-Complex/Ag/Polymeric Carbon Nitride Hybrid Photocatalysts for Visible-Light CO2 Reduction

Ryuichi Nakada,Rikuya Nagao,Jo Onodera,Xian Zhang,Masahito Oura,Megumi Okazaki,Toshiya Tanaka,Riku Koda,Minato Tanaka,Ken Onda,and Kazuhiko Maeda
Journal of the American Chemical Society  Published: February 5, 2026
DOI:https://doi.org/10.1021/jacs.5c21374

Abstract

Artificial photosynthesis that converts CO₂ into value-added chemicals under mild conditions remains a key goal in sustainable catalysis. Hybrid photocatalysts that integrate molecular CO₂ reduction cocatalysts with semiconductor light absorbers provide a versatile platform to combine molecular-level selectivity with solid-state photostability. However, their quantum efficiencies have generally remained low, partly because side reactions of the molecular component have been overlooked. Here we show that suppressing a photochemical ligand-exchange reaction of a surface-anchored Ru complex, trans(Cl)-[Ru(bpy(CH₂PO₃H₂)₂)(CO)₂Cl₂], markedly enhances photocatalytic CO₂ reduction over a well-established Ag-loaded polymeric carbon nitride hybrid. The suppression of this undesirable photochemical reaction is achievable under low-intensity visible light when the Ru complex is loaded at a high density. The optimized system achieves selective CO₂-to-formate conversion with an apparent quantum yield of 27.7% at 400 nm and a formate selectivity greater than 99%. Spectroscopic analyses reveal that the suppression of photochemical ligand exchange maintains the original Ru coordination environment with large driving force for CO₂ reduction, thereby stabilizing the catalytic cycle and facilitating efficient interfacial electron transfer. These results reveal an unrecognized limitation in molecule/semiconductor hybrid photocatalysts─photochemical ligand exchange of the molecular cocatalyst─and demonstrate that controlling such side reactions offers an important strategy to design high-efficiency CO₂ reduction systems.