Publication Date

5-15-2020

Department

Ames Laboratory; Chemistry

Campus Units

Chemistry, Ames Laboratory

OSTI ID+

1616739

Report Number

IS-J 10207

DOI

10.1021/acscatal.0c00899

Journal Title

ACS Catalysis

Volume Number

10

Issue Number

10

First Page

5707

Last Page

5714

Abstract

A mechanistic study of heterogeneous tandem catalytic systems is crucial for understanding and improving catalyst activity and selectivity but remains challenging. Here, we demonstrate that a thorough mechanistic study of a multistep reaction can guide us to the controllable selective synthesis of phenyltetrahydroquinoline or phenylquinoline with easily accessible precursors. The one-pot production can be achieved, catalyzed by a well-defined, bifunctional metal–organic framework-supported Pd nanoparticles, with only water as the side product. Our mechanistic study identifies six transient intermediates and ten transformation steps from the operando magic angle spinning nuclear magnetic resonance study under 27.6 bar H2. In particular, reactive intermediate 2-phenyl-3,4-dihydroquinoline cannot be observed with conventional chromatographic techniques but is found to reach the maximal concentration of 0.11 mol L–1 under the operando condition. The most probable reaction network is further deduced based on the kinetic information of reaction species, obtained from both operando and ex situ reaction studies. This deep understanding of the complex reaction network enables the kinetic control of the conversions of key intermediate, 2-phenyl-3,4-dihydroquinoline, with the addition of a homogeneous co-catalyst, allowing the selective production of tetrahydroquinoline or quinoline on demand. The demonstrated methods in this work open up new avenues toward efficient modulation of reactions with a complex network to achieve desired selectivities.

DOE Contract Number(s)

AC02-07CH11358

Language

en

Publisher

Iowa State University Digital Repository, Ames IA (United States)

Available for download on Wednesday, March 17, 2021

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