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Inorganic Chemistry
pubs.acs.org/IC
Article
Catalysis Experiments of MOF 2. MOF 2 was first immersed in
toluene for 30 min before the catalytic reaction to remove other
solvents on the surface of MOFs. Then these samples were filtered
and directly dried in air. Various substrates (1.0 mmol), malononitrile
(1.1 mol), and MOF 2 were all mixed in a bottle glass containing
toluene (6 mL) and heated at 80 °C for 4 h. The yield can be well
determined by GC with biphenyl as the internal standard. The
recyclability of MOF 2 was continuously reused after each catalytic
reaction.
Analysis of Single Crystal Structure. Single crystals with high
quality were selected to measure their structures on a Bruker SMART
APEX II with Cu Kα radiation. Single data were corrected by the
multiscan absorption in the application of SADABS.32 Then they were
determined by the direct method and refined through the SHELXTL
program.33 All non-hydrogen atoms were ensured and refined by the
anisotropic approach. The PLATON/SQUEEZE method can be used
to wipe off the poor independent reflections from solvents.34,35 All
data are shown in Table 1.
nonaqueous systems. Thus, it is an urgent task to design and
synthesize highly stable MOFs in the luminescent detection of
antibiotics in water.
In this work, two self-interpenetrating MOFs, [CdL(NO3)2·
4H2O]n (namely, MOF 1) and {[CoL(H2O)3]·2NO3}n
(namely, MOF 2) can be prepared based on a trigonal ligand
tris(4-(4H-1,2,4-triazol-4-yl)phenyl)amine (namely, L). They
both exhibit interesting three-dimensional (3D) constructions
with the 1 + 2 self-locked mode. This ligand does not merely
have various N-donors as Lewis basic catalytic sites but also
exhibits an obvious luminescent property. MOF 1 possesses
luminescent properties from the ligand because of CdII with
the d10 outer electron and exhibits excellent water stability,
resulting in that it can be implemented as a sensor in the
detection of nitrofurantoin (NFT) in aqueous solution with
favorable recyclability, selectivity, and sensitivity. MOF 2, as a
Lewis basic catalyst, displays a superior catalytic ability for the
Knoevenagel reaction with excellent reusability for at least five
cycles.
Table 1. Crystal Data of MOFs 1 and 2
compound
1
2
empirical formula
formula weight
crystal system
space group
a (Å)
b (Å)
c (Å)
α (deg)
β (deg)
C24H26O10N12Cd
755
monoclinic
C2y
27.6524(9)
15.3074(4)
9.0504(3)
90
103.559(3)
90
3724.1(2)
4
1.218
5.109
6950
C24H18O3N10Co
553.41
monoclinic
C2y
26.668(4)
14.944(2)
9.1400(15)
90.00
100.944(14)
90.00
3576.4(10)
4
1.028
4.050
4885
EXPERIMENTAL SECTION
■
Materials and Analysis. Chemicals in this work were purchased
directly. Tris(4-(4H-1,2,4-triazol-4-yl)phenyl)amine was prepared
according to a previous report.31 Thermogravimetric (TGA) curves
were collected on a SDT-Q600 analyzer. Powder X-ray diffraction
(PXRD) profiles were obtained on a Siemens Bruker D5000 X-ray
powder diffractometer. The luminescent spectra were implemented
on a Horiba FluoroMax 4 spectrometer. UV−Vis adsorption spectra
were acquired on a Shimadzu UV−2450 spectrophotometer. Catalytic
data were calculated on a GC-6890B gas chromatograph machine.
Elemental analyses were carried out on a PerkinElmer 240 analyzer.
Preparation of [CdL(NO3)2·4H2O]n (MOF 1). Cd(NO3)2·4H2O
(0.03 g) and L (0.015 g) were both mixed in a mixed solution of H2O
(1.2 mL) and ethanol (3.8 mL) in a Teflon-lined autoclave, which was
still heated in an oven at 165 °C for 1 week. After it slowly cooled to
room temperature at 10 °C h−1, the light yellow crystals were
collected and dried in air. The yield was ∼59% based on this ligand.
Element analysis of C, H, and N (%): H, 4.21; C, 37.89; N, 22.11;
Found: H, 4.27; C, 37.94; N, 22.06.
Preparation of {[CoL(H2O)3]·2NO3}n (MOF 2). Co(NO3)2·6H2O
(0.03 g) and L (0.015 g) were putted in ethanol (4 mL) and H2O (1
mL), which was all added in a Teflon-lined autoclave. The system was
heated in an oven at 165 °C for a 1 week. After this autoclave was
cooled down to room temperature at a decreasing temperature rate of
10 °C h−1, violet crystals were generated and dried in air. The yield is
∼64% based on this ligand. Element analysis of C, H, and N (%): H,
4.35; C, 41.80; N, 24.38; Found: H, 4.41; C, 41.72; N, 24.32.
Sensing Experiments of MOF 1. Before these luminescence
sensing trials, as-synthesized crystals were gradually ground to reduce
their sizes in a mortar before luminescent sensing experiments, which
can directly enhance the dispersity of MOF 1 in water. The
suspension of ground samples in water (0.3 mg mL−1) was
successfully obtained by adding 9 mg of ground crystals into 30 mL
of water, which was continuously stirred for 20 min and then treated
by ultrasonication for 20 min. All luminescent experiments of MOF 1
were measured under the excitation of 348 nm. Luminescent signals
were collected with or without antibiotics in water for 2 min at 0.05
mM, including nitrofurantoin (NFT), dimetridazole (DTZ),
sulfamethazine (SMZ), florfenicol (FFC), penicillin (PCL), chlor-
amphenicol (CAP), and thiamphenicol (THI). The relationship
between spectral intensities and concentrations were performed and
analyzed by gradually adding antibiotics into the detectable system.
The recyclability was measured and investigated by detecting
antibiotics at 0.05 mM. After each sensing experiment, MOF 1 was
able to be centrifugally obtained and regenerated by washing with
water.
γ (deg)
V (Å3)
Z
ρ calc g cm−3
μ (mm−1
Nref
)
F(000)
R(int)
GOF
R1, wR2 [I > 2σ(I)]
R1, wR2 (all data)
1368.0
0.028
1.010
0.0396, 0.1072
0.0409, 0.1093
1132.0
0.0564
1.127
0.1185, 0.3004
0.1322, 0.3309
RESULTS AND DISCUSSION
Structure of [CdL(NO3)2·4H2O]n (MOF 1). MOF 1 is the
C2y space group and the monoclinic crystal system. There is
■
−
one Cd atom, one L, and two coordinated NO3 ions in the
asymmetrical unit. The Cd atom is connected with three N-
donors in three ligands and four O-donors atoms from two
−
NO3 ions; meanwhile, the organic linker is linked with three
Cd atoms through the Cd−O coordination bond with the bind
mode of μ3-η1: η1: η1 (Figure 1a). Only one N atom in the five-
ring of the linker is connected with one Cd atom, resulting in
another N atom free in the five-ring motif. The mononuclear
Cd is connected with the bridging linkers to construct a two-
dimensional (2D) network with hexagonal pores with a length
of ∼9.7 Å (Figure 1b). The Cd···Cd distance in MOF 1 in this
2D layer is ∼16.5 Å. Because of the large pore size, an 1 + 2
self-locked structure can be found to construct a three-
dimensional (3D) network (Figure 1c−e).
Structure of {[CoL(H2O)3]·2NO3}n (MOF 2). The single
crystal data show that MOF 2 crystallizes in the C2y space
group and the monoclinic system. The asymmetrical unit of
MOF 2 contains one Co atom, one linker, and three
B
Inorg. Chem. XXXX, XXX, XXX−XXX