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Poly(ethyleneimine)‐tethered Ir Complex Catalyst Immobilized in Titanate Nanotubes for Hydrogenation of CO 2 to Formic Acid
Author(s) -
Kuwahara Yasutaka,
Fujie Yuki,
Yamashita Hiromi
Publication year - 2017
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201700508
Subject(s) - catalysis , formic acid , ethyleneimine , titanate , materials science , chemical engineering , heterogeneous catalysis , chemistry , inorganic chemistry , nuclear chemistry , organic chemistry , ceramic , engineering , polymer
Production of formic acid (FA) by hydrogenation of CO 2 using a ternary hybrid catalyst, poly(ethyleneimine)‐tethered Ir‐iminophosphine complex (Ir‐PN‐PEI) immobilized in titanate nanotubes (TNTs), is reported. On the basis of comprehensive structural analyses, we show that Ir‐PN‐PEI is tightly immobilized within the cavity space of TNT without affecting the electronic/coordination states of Ir atoms. Liquid‐phase CO 2 hydrogenation under pressurized CO 2 and H 2 demonstrates that the Ir‐PN‐PEI catalyst immobilized in Na + ‐type TNT exhibits the highest FA yields (TON>1000 for 20 h under mild reaction conditions (2.0 MPa, 140 °C)) and improved reusability, which far outperform those of unimmobilized prototype Ir‐PN‐PEI. The improved catalytic performance is attributed to the ability of TNT to efficiently capture CO 2 and to stabilize PEI, with Na + ‐type TNT with higher basic property providing a more productive effect. The catalyst is reusable over multiple cycles with activity comparable to those of heterogeneous catalysts previously reported, rendering this material suitable for efficient transformation of CO 2 into FA.