Zhi-Feng Jiao, Ya-Ming Tian, Xiao-Ning Guo et al.
Journal of Catalysis 395 (2021) 258–265
is characterized by a high extinction coefficient for light absorption
and large electric fields at the particle surface [55–66], resulting in
the formation of energetic charge carriers in the nanoparticles with
high efficiency, leading to chemical transformations. Ye et al.
developed an efficient plasmonic Cu/ZnO photocatalytic reduction
the reaction and exposed to a Xenon lamp (PLS-SXE300C/CUV, Bei-
jing Perfect Light Scientific and Technical Co. Ltd). A low-pass opti-
cal filter was employed to block light with k < 400 nm. The light
2
intensity was maintained at 0.6 W/cm . The effect of the wave-
length of light on catalytic performance was investigated using
various low pass optical filters to block light below specific cutoff
wavelengths and using various light-emitting diode (LED) lamps
with different wavelengths, respectively. For the former, employ-
ing a filter with a cut-off wavelength of 450 nm as an example,
blocks light with wavelengths < 450 nm (the reaction mixture
was irradiated by light with wavelengths between 450 and
800 nm). During this process, the light intensity without filtering
for the reaction remained unchanged.
2
of CO to methanol at ambient pressure [65]. Our previous studies
showed that Cu nanoparticles supported on graphene exhibit high
photocatalytic activities for the coupling of nitroaromatics [58],
aerobic oxidation of amines [60] and N-arylation of imidazoles
[
61] under visible light irradiation. Because photocatalysis has
the possibility to generate highly reactive intermediates, and then
to achieve reactions that are difficult through conventional
ground-state pathways, and studies in both homogeneous and
heterogeneous catalysis have shown that Cu works well for the
borylation of alkyl halides, we therefore hoped to achieve the bory-
lation of alkyl halides using Cu nanoparticles as the photocatalyst.
After reaction, the reaction mixture was diluted with dichloro-
methane (DCM, 10 mL), and filtered through a millipore filter (pore
size: 0.22 lm), and n-dodecane (34 mg, 0.2 mmol) was added as an
internal standard. The product yields were determined by gas
chromatography-mass spectrometry (GC–MS, BRUKER SCION SQ
2
. Experimental
4
56 GC–MS) using n-dodecane as the internal calibration standard.
The values given are the average of two experiments. The yields
were calculated based on the amount of alkyl halide. The residue
was purified by column chromatography on silica gel (silica:
2
.1. General information
All reagents were purchased from Energy Chemical, Aladdin,
2
00–300; eluant: hexane/ethyl acetate) to isolate the desired
product.
All NMR spectra were recorded at ambient temperature using
Alfa-Aesar, Aldrich or ABCR, and were checked for purity by GC–
MS and/or H NMR spectroscopy and used as received.
1
1
13
1
Bruker DRX-300 ( H, 300 MHz; C{ H}, 75 MHz) and Bruker
Avance III 400 ( H, 400 MHz; C{ H}, 100 MHz) NMR spectrome-
ters. H NMR chemical shifts are reported relative to TMS and were
2
.2. Preparation of Cu2.8Pd0.2/graphene
1
13
1
1
The Cu2.8Pd0.2/graphene catalyst was prepared by a high-
referenced via residual proton resonances of the corresponding
temperature liquid-phase oleylamine reduction method. Briefly,
8
5
sonication, the mixture was heated to 230 °C for 6 h under reflux.
After cooling to room temperature, the solid product was then sep-
arated, washed and dried to obtain the Cu2.8Pd0.2/graphene catalyst
with Cu loading of 2.8 wt% and Pd loading of 0.2 wt% based on the
amount of metal in the precursor. The exact loading of Cu and Pd
were determined to be 2.74 wt% and 0.17 wt%, respectively, by
inductively coupled plasma-mass spectroscopy (ICP-MS, Perkin-
Elmer ELAN 5000). Cu
graphene and Pd /graphene were prepared following the same
procedures as those for Cu2.8Pd0.2/graphene, except that different
amounts of the corresponding metal salt precursors were used.
The subscripts in different catalysts refer to the mass loading level
of the corresponding metal.
13
1
deuterated solvent (CDCl
tra are reported relative to TMS via the carbon signals of the
deuterated solvent (CDCl : 77.16 ppm). However, signals for the
carbon attached to boron, C(aryl)-B, are usually too broad to
3
: 7.26 ppm) whereas C{ H} NMR spec-
.8 mg of [Cu(OAc)
2
ꢀH
2
O] and 97 mg of graphene were added into
0 mL of Pd(NO oleylamine solution (0.037 mmol/L). After 1 h of
3 2
)
3
13
1
11
observe in the C{ H} NMR spectra. B NMR chemical shifts are
19
quoted relative to BF
shifts are quoted relative to CFCl
3
ꢀEt
2
O as external standard. F NMR chemical
13
3
1
as the external standard. All
C
NMR spectra were broad-band H decoupled. HRMS were mea-
sured on a Thermo Scientific Exactive Plus equipped with an Orbi-
trap. ESI measurements were conducted using a HESI Source with
an aux-gas temperature of 50 °C. Measurements were conducted
using an APCI Source with a Corona Needle; aux-gas temperature
was 400 °C.
3
/graphene, Cu2.9Pd0.1/graphene, Cu2.5Pd0.2/
3
2.4. EPR measurements
The microstructures of the catalysts were investigated by high-
resolution transmission electron microscopy (HRTEM) and high-
angle annular dark field scanning transmission electron microcopy
For EPR measurements, 0.2 mmol of 3-phenylpropyl bromide,
0
3
.24 mmol of B
2 2
pin , 0.4 mmol of LiOtBu, 0.4 mmol of DMPO,
mg of Cu2.8Pd0.2/graphene, and 5 mL of DMF were mixed and
placed in a quartz reactor. The mixture was irradiated by a
PE300BF Xe lamp source with a light intensity of 0.8 w/cm2 for
(
HAADF-STEM). EELS were collected on a 200-kV ARM 200F STEM
under vacuum. X-ray photoelectron spectroscopy (XPS) was mea-
sured on a Kratos XSAM800 spectrometer, using an Al K
= 1486.6 eV) X-ray source as the excitation source. The crys-
talline phases were characterized by X-ray diffraction (XRD, Rigaku
D-Max/RB). UV–Vis absorption spectra were measured with Al
as the reference using a UV-3600 spectrophotometer (Shimadzu).
a
3
min, and then the EPR measurement at X-band (9.86 GHz) was
(hm
carried out using a Bruker EMXPLUS10/12 EPR spectrometer at
room temperature. Another EPR measurement was also conducted
using the same method, but without the Cu2.8Pd0.2/graphene
catalyst.
2 3
O
2.3. Photocatalytic reactions
3
. Results and discussion
Unless specified otherwise, the reactions were conducted under
air with a pressure of 1 atm. A mixture of 1 mmol of alkyl halides,
mmol of LiOtBu, 1.2 mmol of B pin and 15 mg of Cu2.8Pd0.2
Graphene-supported Cu nanoparticles with a 3 wt% loading
level (Cu /graphene) were prepared by a liquid reduction method,
3
2
2
2
/
graphene catalyst was dissolved in DMF (10 mL) in a photocatalytic
reactor equipped with a magnetic stirring bar. The reaction tem-
perature was set at 30 °C for alkyl bromides and 50 °C for alkyl
chlorides, respectively, and controlled by a circulating water bath
and were employed for the borylation of 1-bromo-3-
phenylpropane (1a) and 1-chloro-3-phenylpropane (1a’) with
B pin at 30 °C in air under irradiation by a Xe lamp with a wave-
2 2
length range of 400 to 800 nm, which gave 40% and 22% yields of 1-
(
RT4 circulator, ASONE). The mixture was stirred at 700 rpm during
Bpin-3-phenylpropane (1b) after 2 h and 9 h (Table 1, entry 2),
259