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CO 2 Capture and Conversion with a Multifunctional Polyethyleneimine‐Tethered Iminophosphine Iridium Catalyst/Adsorbent
Author(s) -
McNamara Nicholas D.,
Hicks Jason C.
Publication year - 2014
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201301231
Subject(s) - catalysis , ligand (biochemistry) , chemistry , iridium , formate , denticity , amine gas treating , formic acid , combinatorial chemistry , imine , phosphine , metal , polymer chemistry , organic chemistry , biochemistry , receptor
Tunable, multifunctional materials able to capture CO 2 and subsequently catalyze its conversion to formic acid were synthesized by the modification of branched polyethyleneimine (PEI) with an iminophosphine ligand coordinated to an Ir precatalyst. The molecular weight of the PEI backbone was an important component for material stability and catalytic activity, which were inversely related. The amine functionalities on PEI served three roles: 1) primary amines were used to tether the ligand and precatalyst, 2) amines were used to capture CO 2 , and 3) amines served as a base for formate stabilization during catalysis. Ligand studies on imine and phosphine based ligands showed that a bidentate iminophosphine ligand resulted in the highest catalytic activity. X‐ray photoelectron spectroscopy revealed that an increase in Ir 4f binding energy led to an increase in catalytic activity, which suggests that the electronics of the metal center play a significant role in catalysis. Catalyst loading studies revealed that there is a critical balance between free amines and ligand–metal sites that must be reached to optimize catalytic activity. Thus, it was found that the CO 2 capture and conversion abilities of these materials could be optimized for reaction conditions by tuning the structure of the PEI‐tethered materials.