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J. He et al. / Journal of Catalysis 376 (2019) 161–167
tron spectrometer, using monochromatized Al Ka (hm = 1486.7 eV)
as the excitation source. Mott–Schottky measurements were tested
on a CHI 760E electrochemical workstation (Shanghai Chenhua
Instrument Co., China) in a three-electrode electrochemical cell
using a 0.1 M Na2SO4, temperature. 1H NMR spectra were recorded
on a Varian INOVA-400 MHz type (1H, 400 MHz) spectrometer. The
chemical shifts are reported in ppm relative to CHCl3 (d = 7.26) for
1H NMR. Optical rotation was measured on a PerkinElmer 241
polarimeter. The photocatalytic reaction were performed on
WATTCAS Parallel Light Reactor (WP-TEC-1020HSL) with 10 W
COB LED.
Scheme 1. The design concept for obtaining photocatalysts and representation of
selective benzylamine and olefins oxidation over ZnW–DPNDI–PYI by
photocatalysis.
2.3. X-ray crystallographic analysis
Crystal with dimensions 0.20 ꢂ 0.13 ꢂ 0.05 mm for ZnW–
DPNDI–PYI was stuck on a glass fiber, and intensity data were col-
lected at 296(2) K on a Bruker Smart APEX II CCD diffractometer
Herein, a new POM-incorporated metal-organic framework
(POMOF) {[Zn(HPYI)3]2(DPNDI)}[BW12O40 2
Cat-1, for short) was synthesized by assembling the [BW12O40
]
(ZnW–DPNDI–PYI or
5ꢀ
]
with graphite-monochromated Mo K
a radiation (k = 0.71073 Å).
anion, zinc (II) ion, DPNDI and PYI within a single framework
(Scheme 1). It is ideally suited for heterogeneous photocatalytic
conversions owing to the electron donor and acceptor orderly
Routine Lorentz polarization and Multi-scan absorption correction
was applied to intensity data. Its structure was determined and the
heavy atoms were found by direct methods using the SHELXTL-97
program package [33]. The remaining atoms were found from suc-
cessive full-matrix least-squares refinements on F2 and Fourier
syntheses [34,35]. Positions of the hydrogen atoms attached to car-
bon and nitrogen atoms were geometrically placed. All hydrogen
atoms were refined isotropically as a riding mode using the default
SHELXTL parameters. Crystallographic data for ZnW–DPNDI–PYI
were summarized in Table S1.
embedded within
anionꢁ ꢁ ꢁ and CAHꢁ ꢁ ꢁanion interactions between trapped POM
anions and –acidic DPNDI skeletons can promote charge transfer
a photoactive framework. The directional
p
p
among components, which should contribute to the activation of
O2 [27]. Through conPET process, DPNDI will first form radical
anion DPNDIÅꢀ*, then the DPNDIÅꢀ* acts as an electron transporter
to transfer electrons to the POM anion [28]. POM anion will act
as the electron receiver, which determines the generation of O2Åꢀ
.
PYI moiety in the POMOF will promote the generation of the
DPNDIÅꢀ as electron donor. In addition, the energy transfer (ET)
gives rise to 1O2 generation over naphthalene units by light irradi-
ation [29]. The synergy of 1O2 and OÅ2ꢀ is beneficial to the excellent
catalytic activity and selectivity under ambient conditions.
2.4. Photocatalysis
2.4.1. Typical procedure for the photocatalytic oxidation of amines
A glass tube was filled with amines (5 mmol), ZnW–DPNDI–PYI
(14 lmol, 0.03 mol%) and acetonitrile (3 mL). The mixture was
exposed to a 10 W white LED lamp placed at a distance of 5 cm
under air at room temperature. After reaction for 16 h, the mixture
was centrifuged to remove ZnW–DPNDI–PYI and dried in vacuo.
The yield was calculated by integration of the characteristic 1H
NMR peaks of substrates and products.
2. Experimental
2.1. 2.1 preparation
All reagents were used as purchased without further purifica-
tion. L–N-tert-butoxy-carbonyl-2-(imidazole)-1-pyrrolidine (L–
BCIP) [30], DPNDI [31] and K5[BW12O40]ꢁ5H2O [32] were prepared
according to literature methods and characterized by IR and 1H
2.4.2. Typical procedure for the photocatalytic oxidation of olefins
A glass tube was filled with styrene (5 mmol), ZnW–DPNDI–PYI
(14 lmol, 0.03 mol%) and CH3CN (3 mL). The mixture was exposed
to a 10 W white LED lamp placed at a distance of 5 cm under air at
room temperature. After reaction for 12 h, the mixture was cen-
trifuged to remove ZnW–DPNDI–PYI and dried in vacuo. The yield
was calculated by integration of the characteristic 1H NMR peaks of
substrates and products.
NMR. Mixture of Zn(NO3)2ꢁ6H2O (44.6 mg, 0.15 mmol), K5[BW12
-
O40]ꢁ5H2O (157.8 mg, 0.05 mmol), DPNDI (23.4 mg, 0.15 mmol)
and L–BCIP (24.5 mg, 0.1 mmol) for ZnW–DPNDI–PYI in mixed
water (4.0 mL) and methanol (2.0 mL) was stirred. The resulting
suspension was sealed in a 25 mL Teflon-lined reactor and kept
at 120 for four days. After cooling the autoclave to room temper-
ature, aqua rod-like single crystals were separated, washed with
water and air-dried. (Yield: ca. 60% based on K5[BW12O40]ꢁ5H2O).
Elemental analyses (EA) and ICP calcd (%) for C40H54N14O41W12Zn3:
C 12.68, H 1.44, N 5.18, Zn 5.18, W 58.22; Found: C 12.64, H 1.41, N
5.20, Zn 5.22, W 58.24 for ZnW–DPNDI–PYI.
3. Results and discussion
Solvothermal reaction of Na5[BW12O40], Zn(NO3)2, L–BCIP and
DPNDI gave ZnW–DPNDI–PYI in a yield of 60%. Elemental analyses
and powder X-ray analysis (XRD) indicated the pure phase of its
bulk sample (Fig. S1). Single-crystal structural analysis revealed
that ZnW–DPNDI–PYI crystallizes in the chiral space group P21
2.2. Characterizations
EA of C, H and N were performed on a Vario EL III elemental
analyzer. ICP analyses were performed on a Jarrel-AshJ-A1100
spectrometer. FT-IR spectra were recorded as KBr pelletson JASCO
FT/IR-430. Powder XRD diffractograms were obtained on a Riguku
D/Max-2400. Circular dichroism (CD) spectrum was measured on
JASCO J-810. UV–Vis spectra were recorded on a HP 8453 spec-
trometer. Fluorescent spectra were measured on EDINBURGH
F900. The X-ray photoelectron spectroscopy (XPS) measurements
were conducted using an ESCALAB 250Xi high-performance elec-
(Table S1). The asymmetric unit of ZnW–DPNDI–PYI consists of
5–
one cation {[Zn(HPYI)3]2 (DPNDI)}10+ and two [BW12O40
]
anions
(Fig. 1a). Each zinc ion adopts a tetrahedron geometry with four
nitrogen atoms from three protonated PYI and one DPNDI
(Fig. S2). The Keggin polyanions typically reside directly over the
electron-deficient naphthalene ring centroid with centroid dis-
tance 3.0 Å (Fig. S3). PYI is in-situ generated with the butoxycar-
bonyl of BCIP removed in the reaction and the pyrrolidine
nitrogen was protonated [36]. The intramolecular strong hydrogen