Reactive and Functional Polymers
Perspective Article
Phenanthroline functionalized polyacrylonitrile fiber with Pd(0)
nanoparticles as a highly active catalyst for the Heck reaction
*
Jian Xiao, Haonan Zhang, Anyaegbu Chima Ejike, Lu Wang, Minli Tao , Wenqin Zhang
Department of Chemistry, School of Sciences, Collaborative Innovation Center of Chemical Science and Engineering, Tianjin University, Tianjin 300072, PR China
A R T I C L E I N F O
A B S T R A C T
Keywords:
A series of polyacrylonitrile fibers (PANF) functionalized with nitrogen-containing ligands were prepared and
then used to synthesize fiber-supported Pd(0) nanoparticle catalysts. The phenanthroline-functionalized PANF
with immobilized Pd(0) nanoparticles (PANPhenF-Pd(0)) had the best catalytic activity for the Heck reaction
under solvent-free conditions. The PANPhenF-Pd(0) efficiently stabilized the nanoparticles and they were well-
dispersed with Pd(0) particle sizes of about 3 nm. The PANPhenF-Pd(0) structure was further characterized by
a variety of instrumental methods. A probable mechanism based on the fiber’s microenvironment is proposed for
the Heck reaction catalyzed by PANPhenF-Pd(0). The PANPhenF-Pd(0) catalyst is easily recovered from the re-
action system and can be used up to six times with only a slight decrease in catalytic activity and with low Pd
leaching. The PANPhenF-Pd(0) catalyst also has excellent catalytic activity for gram-scale use.
Polyacrylonitrile fiber
Palladium nanoparticles
Heck reaction
Solvent-free
Gram-scale production
1
. Introduction
catalytic properties than homogenous catalysts, many of them have
chemical stability and poor recyclability. Therefore, preparing improved
The Heck reaction is an important method for forming C
–
C bonds
supports for Pd(0) nanoparticles is a valuable research area.
[
1], and has been used for the synthesis of many new types of drugs
Polyacrylonitrile fiber (PANF) is a cheap commercially available
synthetic fiber that has a soft texture and good mechanical strength [41].
It is made from at least 85% acrylonitrile and a copolymer which pro-
duces many cyano groups in the fibers. This makes PANF easy to modify
using common reactions. These excellent properties make PANF an ideal
carrier for heterogeneous catalysts. In our previous work, many func-
tionalized PANF-catalysts have been designed including PANF-
supported acid and base catalysts [42–48], PANF-supported inexpen-
sive metal catalysts [49,50], and PANF-supported phase transfer cata-
lysts [51]. All of these catalysts have excellent catalytic abilities with
good recyclability.
including montelukast (antiasthma agent), naproxen (anti-inflamma-
tory) [2], eletriptan (antimigraine) [3] and rilpivirine (anti-AIDS) [4].
Many organometallic catalysts have been used to efficiently catalyze
Heck reactions, such as compounds containing copper [5], nickel [6,7],
cobalt [8,9], and palladium [10–21]. Among them, palladium catalysis
are the most efficient and have been widely studied by researchers.
However, palladium is expensive and these catalysts are difficult to
recycle in homogeneous reaction systems. Additionally, as a heavy
metal, palladium is poisonous and can cause serious environmental
problems if it is released into nature [22]. From an economical and
environmental standpoint, it is of great importance to develop a recy-
clable palladium catalyst.
Interestingly, it has been shown that carriers containing organic li-
gands have a very positive impact on the dispersion and stability of Pd
(0) nanoparticles and on the catalytic activity of these Pd catalysts
[52–58]. Although aza ligands have weaker coordination abilities than
phosphine ligands, they are much cheaper than phosphine ligands and
can be easily immobilized on PANF [59–62]. Therefore, in this work, a
series of PANFs functionalized with aza ligands were prepared using a
simple method and then Pd(0) nanoparticles were stabilized on each of
these samples (Scheme 1). The catalytic activities of these PANF-Pd(0)
nanoparticle catalysts were investigated for the Heck reaction. The
Traditionally Pd(0) has played a vital role in catalyzing Heck re-
actions and the preparation of catalysts with supported Pd(0) particles
catalysts has found many applications [23,24]. Various carriers
including silica [25], GO [26,27], polymers [28–30], magnetic Fe
3 4
O
[
[
31–33], MOFs [34–36], carbon nanotube [37] and composite materials
38–40] have all been used to prepare heterogeneous palladium cata-
lysts. Compared with supported Pd(II) catalysts, these carriers can hold
Pd(0) more tightly. Although these heterogeneous catalysts have better
*
Received 24 September 2020; Received in revised form 21 January 2021; Accepted 29 January 2021
Available online 3 February 2021
1
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