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center on the imidazole was exploited for nanomolar TNP
sensing. To the best of our knowledge, no examples of MOFs
having pyramidal NO3− ions in SBUs are reported in the
literature.
cage reveals a hexagonal [In (μ-OH) (NO ) ] sheet capped
1
8
12
3 6
with triangular [In (μ-OH) (NO )] units to form a
9
6
3
cuboctahedron. The capped triangular units are anti to each
−
other, wherein the NO ions are present in the C vertices.
3
3
−
The linker H Imtb was synthesized and characterized
Thus, the NO3 ions’ orientation controls the arrangements of
linear In (μ-OH) within the layers of the MOF.
Further scrutiny of the NO
3
thoroughly by spectroscopic, spectrometric, and elemental
3
2
−
analysis [see SI]. Reactions of H Imtb with In(NO ) ·xH O
3
ion orientation enumerates
3
3 3
2
were carried out under different experimental conditions such
as (a) stoichiometric ratios of ligand to metal (1:1; 1:2; 1:3
etc.), (b) modulating agents, like CH COOH, HNO ,
that it exhibits an atypical pyramidal geometry (Figure 1c).
−
The adjacent NO
ions in hexagonal sheets adopt an anti-
45
3
conformation (like umbrella inversion). Also, within the
layers (a−f), these ions are related to each other by their shape
and the torsional angles between ONNO atoms. Overall, this
3
3
CF COOH, H PO , and HBF , and (c) solvents DMF and
3
3
4
4
DMF/H O mixture. The single crystals of In(Imtb)-MOF
2
suitable for X-ray diffraction (SC-XRD) studies were obtained
in the case of H Imtb, In(NO ) ·xH O (in the ratios 1:2.23,
leads to the formation of a dodecawheel type of arrangement of
−
[(NO
)
4
] ions (Figure 1d).
3
3 3
2
3
1
:3, and 1:4), HBF , and DMF. Analysis of the IR spectrum
Within the indium trimer, the In−O distances of indium
[In1 and In2] and carboxylate ions [In1−O1, 2.145(4) Å;
In1−O3, 2.159(4) Å; In2−O4, 2.141(4) Å; In2−O6, 2.143(5)
Å; In1−O1, 2.145(4) Å; In1−O3, 2.159(4) Å; In1−O5,
4
−
1
−1
41
2
−1
Also, the appearance of a peak at 3645 cm stipulates the
42
2
.186(5) Å; In2−O4, 2.141(4) Å; and In2−O6, 2.143(5) Å]/
presence of the In−OH group. However, the exact structural
The solid-state structure of In(Imtb)-MOF shows a unique
SBU having a composition of [In (μ-OH) (OH ) (NO )-
OH ions [In1−O7, 2.082(4) Å; In2−O7, 2.077(4) Å] or water
molecules [In1−O9, 2.194(7) Å] are well within the reported
4
2
values. However, the In−O bond distance in In-ONO
2
[
In1−O8, 2.081(6) Å] is shorter than the monodentate
9
6
2 6
3
−
46
−
binding of the NO ion to the indium atom [2.143(2) Å].
(
[
(
Imtb) ], in which the NO3 ion with a longer N−O bond
3
6
−
The TGA of activated In(Imtb)-MOF shows thermal
stability up to 480 °C. Also, the VT-PXRD study confirms
the crystallinity of the sample up to 240 °C. The aqueous
stability of the MOF was ascertained for 7 days and
N3−O8:1.477 (6) Å compared to free NO3 (N−O: 1.258
7) Å)] is bridging the three different In (μ-OH) (indium
3
2
40,43,44
trimer) units like the 3.111 type coordination mode.
These indium trimers together with bridged NO3 ions form
−
authenticated through PXRD. The N gas adsorption isotherm
an inorganic hexagonal wave-like pattern [In (μ-
2
1
8
2
1
2
3 6
S11−S15a), with an average pore diameter and total pore
volume of 23.71 Å and 0.311 cc/g, respectively. The larger (2
and 3 Å) and the smallest (1.5 Å) pore size reflected in the
NLDFT calculation value can be accounted for by the space
“
ab” axis to create hexagonal sheets (Figure S9a). Further, the
3−
sheets are linked by (Imtb) to form a 3D network. The
adjacent layers of the 3D network show an offset pattern of
hexagonal indium sheets, which provides a platform for a
S9b]. A single cuboctahedral nanoporous cage consists of
The gas adsorption studies of CO performed at three
2
adsorption, optimization of the cycloaddition reaction of CO2
and epichlorohydrin/styrene oxide using activated MOF as a
catalyst and TBAB as a cocatalyst was carried out at RT/50 °C
1
(
complete conversion of the epoxide. Variation of epoxides with
substituents gave excellent conversion as compared to the
blank experiments in all cases (Tables 1 and S4).
Further, solvent-free multicomponent Strecker synthesis of
acetophenone, aniline, and TMSCN in the presence of
phenyl-2-(phenylamino)-propanenitrile was obtained. The
scope of this reaction was evaluated by varying the different
ketones or substituted anilines. In most cases, the yield of the
products was excellent except when electron-withdrawing
groups were present on acetophenone (Table 2). Both
H Imtb and its In(Imtb)-MOF show characteristic lumines-
3
cence in solids at 429 nm (λ 330 nm) and 452 nm (λ 330
ex
ex
nm), respectively. The luminescence intensity of In(Imtb)-
luminescence of the MOF with different nitrophenols was
evaluated in water, and it shows luminescence quenching with
the highest efficiency (97%) for TNP. Extension of the work to
Figure 1. (a) Cuboctahedron cage, (b) 3D view of In(Imtb)-MOF
connected with (Imtb) , (c) layered nitrate ion arrangements in
MOF, (d) 3D view (starburst).
3−
9
239
Inorg. Chem. 2021, 60, 9238−9242