D. Guo et al.
Journal of Solid State Chemistry 293 (2021) 121770
Scheme 1. Illustration of the synthesis of Co-PPOPs by ketenimine condensation.
number of metal ions to yield related metalloporphyrin complexes
[30–32]. Comparing with that of free base porphyrin, metalloporphyrin
exhibits higher thermal-, chemical-, and photo-stabilities due to its larger
conjugated system [20]. Furthermore, the metals in the core of porphyrin
rings endowed them with potential catalytic activity. For example, the
cytochrome P450 enzyme, bearing the structure of metalloporphyrin, can
catalyze the conversion of alcohols to aldehydes in some organisms [33,
In this context, here we synthesized a porous organic framework
based on the Schiff base condensation between 5,10,15,20-tetra(4-ami-
nophenyl)porphyrin (TAPP) and 4,40-biphenyldicarbaldehyde (Scheme
1), which was then coordinated with cobalt to afford the related metal-
loporphyrin complexes (Co-PPOPs). The chemical composition and
morphology of Co-PPOPs were confirmed through various characteriza-
tion methods. Co-PPOPs exhibited high catalytic activity for carbon di-
oxide conversion to cycle carbonate under ambient conditions using a
variety of substrates. Moreover, Co-PPOPs could be reused for several
times without losing any significant activity, demonstrating its good
recycling performance.
yield 20.5%). The TNPP (1.8 g, 2.26 mmol) was dissolved in concen-
trated HCl (30 mL), followed by the dropwise addition of the concen-
trated HCl solution (50 mL) of SnCl2 (7.0 g, 29 mol). The reaction
solution was stirred at room temperature for 2 h, and then heated to 80
ꢀC for 0.5 h under nitrogen atmosphere. After the completion of reaction,
the mixture was cooled to 0 ꢀC, and neutralized with ammonia water. The
purple product was obtained by filtering and Soxhlet extraction with
chloroform (yield 80%). 1HNMR (400 MHz, CDCl3) δ 8.90 (s, 8H), 7.99
(d, J ¼ 8.2 Hz, 8H),7.07 (d, J ¼ 8.2 Hz, 8H), 4.03 (s, 8H), ꢁ2.71 (s, 2H).
MALDI-TOF-MS spectrum of TAPP, calcd for C44H34N8: 674.3122;
Found: 674.3034.
2.2. Synthesis of PPOPs
A Pyrex tube (12 mL) was charged with TAPP (200 mg, 0.26 mmol),
4,40-biphenyldicarbaldehyde (55 mg, 0.52 mmol),1,2-dichlorobenzene
(4 mL), n-butanol (4 mL) and 6 M aqueous acetic acid (0.5 mL). After
sonication for 15 min, the tube was frozen under liquid nitrogen bath,
evacuated and flame sealed. The reaction mixture was then heated at
120 ꢀC for 72 h to afford a reddish-brown precipitate, which was then
purified through Soxhlet extraction using anhydrous THF with solvent
(yield 75%).
2. Experiment section
2.1. Materials and measurements
2.3. Synthesis of Co-PPOPs
All chemicals were reagent-grade, purchased from Aladdin (China)
and used without further purification. Scanning electron microscope
(SEM) images were captured through a JEOL630-F microscope. Trans-
mission electron microscope (TEM) images were recorded by using a
JEM-3010 instrument (JEOL) equipped with slow-scan CCD camera at
300 k eV. The absorption spectra of Co-PPOPs, PPOPs and TAPP
dispersed in DMSO were recorded on a UV–vis Spectrophotometer
(Shimadzu). The X-ray photoelectron spectra (XPS) were carried out by
Multifunctional imaging electron spectrometer (Thermo ESCALAB). The
Fourier transform infrared (FT-IR) spectra were recorded by NICO-
LET6700 spectrometer (ABB Bomen Canada) with KBr pellets. Powder X-
ray diffraction (XRD) patterns were collected on a D8 Advance X-ray
diffractometer (Bruker AXS Germany) with Cu Kr radiation at the speed
of 2ꢀmin ꢁ1. The NMR spectra of cycle carbonates were recorded on a
Varian Mercury-VX 400 spectrometer in CDCl3.
Synthesis of 5,10,15,20-tetra(4-aminophenyl) porphyrin (TAPP).
Under nitrogen atmosphere, a solution of p-nitrobenzaldehyde (11 g,
73 mmol) and acetic anhydride (12 mL, 127 mmol) were dissolved in
400 mL of propionic acid. After heated to 120 ꢀC, pyrrole (5 mL, 73
mmol) was added dropwise and the reaction solution was stirred at 140
ꢀC for 2 h. After cooling to room temperature, the mixture was placed in a
refrigerator overnight, followed by the filtration and washing with
methanol (100 mL ꢂ 3) and deionized water (100 mL ꢂ 3). Subsequently,
the obtained black solid was recrystallized from pyridine, which was then
washed with methanol/acetone (1:1) to obtain purple product (TNPP,
A solution of CoCl2⋅6H2O (200 mg 0.84 mmol) in N-Methyl pyrroli-
done (NMP) (15 mL) was added to a glass flask containing PPOPs (100
mg). After stirring at 80 ꢀC for 48 h, the solution was filtered and the
obtained solid was washed repeatedly with dichloromethane (50 mL ꢂ 3)
and chloroform (50 mL ꢂ 3), respectively. The product was recrystallized
from methanol and then dried under vacuum to afford Co-PPOPs as a
black solid (yield 90%).
2.4. Catalytic test
The catalytic performances of Co-PPOPs were evaluated using various
substrates, such as styrene oxide, 2-(chloromethyl) oxirane, 2-(bromo-
methyl) oxirane and so on. Using styrene oxide as a representative sub-
strate, the catalytic reaction was carried out at room temperature in a 25
mL Schlenk flask. In general, a mixture of tetrabutyl ammonium bromide
(TBAB, 0.58 g, 1.8 mmol), Co-PPOPs (20 mg) and styrene oxide (3.00 g,
25 mmol) was successively added to the flask. CO2 at atmospheric
pressure was then injected through a gas bag. After stirring at room
temperature for 48 h, the reaction mixture was centrifuged and the
insoluble solid were washed with methanol and dichloromethane for
several times. The product yield was determined by gas chromatography
(GC) using chlorobenzene as an internal standard. Further purification of
the crude product was carried out by silica gel column chromatography
to obtain the pure styrene carbonate for NMR characterization.
2