Inorganic Chemistry
Featured Article
efficient CO photoreduction to carbon monoxide (CO) with
double-crankshaft chain with 4-membered rings of Co2B2
(Figure 2d). The adjacent chains are further linked by IPA
in a bis-monodentate fashion to produce a 2D layer (Figure
2e,f). Notably, intrinsic tubelike channels were generated along
the b axis in the layer, and the effective window size of the
channel was about 4.3 × 8.2 Å.
2
−
1
−1
2−
a remarkable rate of 1186.0 μmol·g ·h under visible-light
irradiation. The quenching effects of steady-state photo-
luminescence (PL), combined with photocurrent responses,
confirm that porous BIF-107 can accept photoexcited electrons
from a photosensitizer and provide active catalytic sites for
CO reduction.
In both BIF-106 and BIF-107, the 2D layers as supra-
molecular building units were blocked to generate 3D
frameworks, which were stabilized by the interdigitation of
pendant aromatic rings in phthalate/isophthalate (Figure
3a,b). The 2D layers were blocked in parallel in BIF-106,
resulting in 1D extrinsic pores in the interstitial spaces (Figure
3c). In BIF-107, tubelike channels of the 2D layer have not
been altered by their packing (Figure 3d). Weak C−H···π
interactions were also observed between the aromatic rings in
BIF-107 (Figure 3b). The pore volume ratios were about 18%
and 27% for BIF-106 and BIF-107, respectively, as estimated
2
Crystals of BIF-106 and BIF-107 were synthesized by the
solvothermal reactions of cobalt salts, KBH(mim) , and
3
phthalic acid (PA)/isophthalic acid (IPA), respectively.
Single-crystal X-ray diffraction analysis revealed that both
BIF-106 and BIF-107 possess porous 2D structures, with the
interlayer packing motif stabilized by the interdigitation of
pendant phthalate/isophthalate. The difference of the carbox-
ylate angles between phthalate and isophthalate resulted in
different configurations in the 2D structure. As depicted in
33
with the PLATON program.
The phase purity of these crystals was proven by the well-
the simulated and as-synthesized ones (Figure S1). The solvent
stability was examined by immersion in common solvents, such
as water, ethanol, and acetonitrile (Figure S2). In addition,
both BIF-106 and BIF-107 exhibited excellent chemical
aqueous solutions (pH 2−12; Figure S3). Thermal gravimetric
analysis showed that these crystals can be stable up to 300 °C
under a N atmosphere (Figure S4). CO gas-adsorption
2
2
measurements of BIF-107 exhibit typical type I sorption
3
−1
(
Figure S5). The uptake amounts at 760 Torr are 51.7 cm ·g
3
−1
at 273 K and 30.4 cm ·g at 298 K. The corresponding
Langmuir and Brunauer−Emmett−Teller surface areas for
2
−1
from the adsorption data at 195 K (Figure S12). Furthermore,
the isosteric heat of adsorption (Q ) for CO was calculated as
st
2
−
1
2
1.7 kJ·mol based on the collected adsorption data at 273
Solid-state UV/vis spectral and Mott−Schottky measure-
ments were carried out to determine the energy band position
Figure 1. Coordination environment of the asymmetric unit in (a)
and its possibility for subsequent CO photoreduction. As
2
Co[HBH(mim) ](PA) of BIF-106 and (b) Co[HBH(mim) ](IPA)
3
3
shown in Figure S7, BIF-107 exhibits a broad absorption in the
of BIF-107.
g
eV from the Tauc plot (Figure S8). Mott−Schottky measure-
2
−
imidazolate ligands were protonated during the crystallization
ment (Figure 4a) showed a positive slope of the obtained C
process and Co centers adopted a CoN O2 tetrahedral
values (vs the applied potentials), and the conduction-band
(CB) position was −0.83 eV (vs the normal hydrogen
electrode, NHE), as determined from the intersection point.
The energy position of the CB edge of BIF-107 is more
2
1
2+
includes one crystallographic Co ion, one HBH(im) ligand,
and one deprotonated phthalic acid (PA ) ligand (Figure 1a).
Each Co center is four-coordinated with two N atoms from
3
2−
negative than the reduction potential of CO
vs NHE), and it is theoretically feasible for the photoreduction
of CO to CO (Figure 4b).
to CO (−0.48 eV
2
two different HBH(im) ligands and two O atoms from two
2
3
2
−
2−
different PA ligands. The carboxylate groups of PA
accepted bis-monodentate coordination modes bridging two
Co ions to form Co units (Figure 2a). Then, the HBH(im)
Encouraged by these results, the photocatalytic CO2
reduction over BIF-107 was carried out in an acetonitrile/
water (4:1, v/v) solvent under visible-light irradiation (λ > 420
nm), with [Ru(bpy) ]Cl as the photosensitizer and triethanol-
2
+
2
3
ligands served as μ -bridges to link three Co units, using two
3
2
3
2
N atoms to coordinate to two adjacent Co atoms and the other
amine (TEOA) as the sacrificial electron donor. Remarkably,
N atom to link to the third Co atom according to a N−H···O
BIF-107 exhibited significant activity for CO photoreduction.
2
[
d
= 2.8804(2) Å] hydrogen bond, leading to a 2D planar
The main reduction products were CO and H , as detected by
N−O
2
2
+
sheet (Figure 2b,c). For the structure of BIF-107, the Co
gas chromatography. As presented in Figure 4c, the generation
of CO and H2 increased almost linearly with the light
illumination time. After 5 h of irradiation, the amounts reached
ions and HBH(im) ligands showed the same coordination
3
modes as those in BIF-106 (Figure 1b). The alternating linkage
between the Co and B nodes via mim results in the typical
59.3 μmol for CO and 47.2 μmol for H , with average
2
B
Inorg. Chem. XXXX, XXX, XXX−XXX
Hong, Qin-Long
