Synthesis and Reactivity of Zr MOFs Assembled from PNNNP-Ru Pincer Complexes

Article abstract of DOI:10.1021/acs.organomet.9b00482

Three isostructural Zr metal-organic frameworks have been synthesized from P^NN^NP-Ru pincer metallolinkers bearing different combinations of ancillary ligands (1, Zr₆O₄(OH)₄(OAc)₄{cis-(P

Full text of DOI:10.1021/acs.organomet.9b00482

Article
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Cite This: Organometallics XXXX, XXX, XXX−XXX
Synthesis and Reactivity of Zr MOFs Assembled from PNNNP‑Ru
Pincer Complexes
Abebu A. Kassie,† Pu Duan,‡ Matthew B. Gray,† Klaus Schmidt-Rohr,‡ Patrick M. Woodward,†
and Casey R. Wade*,†
†Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
‡Department of Chemistry, Brandeis University, Waltham, Massachusetts 02453, United States
S
* Supporting Information
ABSTRACT: Three isostructural Zr metal−organic frameworks have
been synthesized from PNNNP-Ru pincer metallolinkers bearing
different combinations of ancillary ligands (1, Zr6O4(OH)4(-
OAc)4{cis-(PNNNP)RuCl2(CO)}2; 2, Zr6O4(OH)4(O2CH)4-
{(PNNNP)RuCl(CO)2}2Cl2; 3, Zr6O4(OH)4(OAc)4{cis-/trans-
(PNNNP)RuCl2(CO)}2; PNNNP = 2,6-(HNPAr2)2C5H3N; Ar = p-
C6H4CO2 ). The structure and composition of the PNNNP-Ru pincer
−
MOFs have been determined using synchrotron X-ray powder
diffraction, solid- and solution-state NMR spectroscopy, IR spectros-
copy, and elemental analysis. Reaction of 2 with KOtBu results in
deprotonation of an NH group of the PNNNP-RuCl(CO)2 linkers.
Subsequent treatment with Me3NO removes a Ru-coordinated CO
ligand, generating 2-b, which proved to be a recyclable catalyst for the
hydrosilylation of aryl aldehydes with Et3SiH. A similar postsynthetic treatment of 1 and 3 does not generate active catalysts,
highlighting the importance of precatalyst design and activation. A homogeneous analogue of 2-b also showed inferior catalytic
performance, demonstrating the benefit of catalyst immobilization.
procedures is perhaps more important for MOF-based catalysts
than for homogeneous systems. First of all, the strategies used
to introduce a catalytic functionality may rely on transition-
metal species with muted reactivity to prevent decomposition
or undesirable side reactions during incorporation. Second,
MOFs and other heterogeneous supports may give rise to
reagent compatibility issues that are not encountered with
homogeneous systems. For example, strong acids or bases may
lead to framework degradation.38,39 In our own experience,
halide ligand abstraction with silver salts has not proven to be
particularly effective with MOFs, in part due to the
precipitation of insoluble silver halide byproducts that are
inseparable from the heterogeneous catalyst.40
Our group and others have been interested in the design and
study of MOFs containing diphosphine pincer complexes.40−47
Diphosphine pincer ligands have been employed for a wide
range of homogeneous catalytic transformations.48−57 They
offer a great deal of electronic and steric diversity as well as
chemical and thermal stability and have been shown to support
catalytically active complexes with nearly all mid-to-late
transition metals. Consequently, the diphosphine pincer ligand
INTRODUCTION
■
Metal−organic frameworks (MOFs) have attracted consid-
erable interest as supports for heterogeneous catalysis owing to
their tunable structures, porosity, and chemical functional-
ity.1−8 The use of well-defined molecular building blocks for
MOF assembly can amalgamate the beneficial traits of
homogeneous and heterogeneous catalyst systems. In addition,
MOFs offer a platform to explore site isolation or secondary
environment effects on the catalytic activity and selectivity of a
catalyst. A diverse range of strategies, including encapsulation,
activation of metal nodes, postsynthetic grafting, and direct
assembly, have been used to functionalize MOFs with
catalytically active transition-metal species.9−22 However,
further postsynthetic steps are still often necessary to activate
MOF-supported precatalysts. In some cases, desolvation
carried out by heating a MOF in vacuo can remove bound
solvent molecules, generating coordinatively unsaturated metal
sites for Lewis acid-catalyzed transformations.23−27 In other
cases, one or more reagent may be required to facilitate
precatalyst activation via X-type ligand exchange or abstraction,
similar to procedures commonly employed for homogeneous
organometallic complexes.28−32 For example, reagents such as
silver salts of weakly coordinating anions have been used to
exchange metal-coordinated halide ligands in MOFs and
organoaluminum or organolithium reagents have been
employed to activate metal nodes for olefin oligomerization
catalysis.33−37 Careful consideration of precatalyst activation
Special Issue: Organometallic Chemistry within Metal-Organic
Frameworks
Received: July 17, 2019
© XXXX American Chemical Society
A
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architecture represents an epitomic platform for the design and
study of a general class of MOF catalysts with the potential for
broad scope catalytic activity.
ATR-IR spectrum. These spectroscopic features are in line
with an analogous PNP-Ru pincer complex reported by
Mashuta and co-workers.61 Treatment of cis-[tBu4L-RuCl-
(CO)2]Cl with a mild oxidative decarbonylating agent,
Me3NO, facilitates loss of a CO ligand, and subsequent
Herein we report the synthesis, characterization, and
preliminary investigation of the reactivity and catalytic activity
of an isostructural series of Zr MOFs (1−3) assembled from
PNNNP-Ru pincer complexes. The new MOFs have been
synthesized from PNNNP-Ru linker precursors containing
different ancillary ligands (chloride, CO, or phosphines).
Despite these differences, solvothermal reactions with ZrCl4
converge to an isostructural series of MOFs that adopt a csq-
type net and are similar to a recently reported Zr MOF
assembled from PNNNP-Co(III) linkers.47 Homogeneous Ru
diphosphine pincer complexes have been widely studied as
catalysts for dehydrogenation, transfer, and direct hydro-
genation of organic transformations.51,58 For many of these
reactions, ligand-based deprotonation is necessary to activate
the Ru diphosphine pincer complexes, and subsequent metal−
ligand cooperativity has been proposed to facilitate key steps in
catalytic cycles.57,59,60 We find that deprotonation followed by
CO ligand removal with Me3NO serves to activate 2 for the
catalytic hydrosilylation of aldehydes with Et3SiH. The other
members of the PNNNP-Ru MOF series as well as
homogeneous analogues of the immobilized pincer complexes
show low activity for the hydrosilylation reaction under similar
precatalyst activation conditions.
deprotection gives H4L-RuCl2(CO).62 The H and 31P NMR
1
spectra of the product indicates a ∼1:3 mixture of cis and trans
isomers.
Synthesis and Characterization of PNNNP-Ru MOFs.
Solvothermal reactions of [H4L-Ru(TFA)(CO)(PPh3)]TFA,
[H4L-RuCl(CO)2]TFA, and cis/trans-H4L-RuCl2(CO) with
ZrCl4 in DMF using CH3CO2H or HCO2H as modulators
yields an isostructural series of MOFs, 1−3, as off-white
microcrystalline powders (Scheme 2). Although 2 could be
Scheme 2. Solvothermal Syntheses and Structural Formulas
of 1−3
RESULTS AND DISCUSSION
■
Synthesis of PNNNP-Ru Complexes. The carboxylate-
functionalized PNNNP pincer ligand Bu4L was synthesized as
t
previously described and used to prepare the series of Ru
synthesized using CH3CO2H as a modulator, we found that
HCO2H provides a more crystalline product. X-ray powder
diffraction (XRPD) analysis indicates that 1−3 adopt csq-type
frameworks that are analogous to a recently reported Zr MOF
assembled from PNNNP-CoCl3 metallolinkers (Figure 1a).47
The framework structure of 1 was interrogated by Rietveld
refinement of synchrotron X-ray powder diffraction (SXPD)
data. Initial indexing provided a hexagonal unit cell (a =
31.937(7) Å, c = 15.798(4) Å), and a structure model was
constructed with P6/mmm space group symmetry on the basis
of the structure of the reported PNNNP-CoCl3 framework.47
Rietveld refinement was carried out using simulated annealing
with a [Zr6O4(OH)4(OAc)4]8+ metal cluster and an idealized
[L-RuCl3]4− linker as rigid bodies. Although the metallolinker
in 1 was identified as [cis-L-RuCl2(CO)]4− on the basis of
NMR and IR spectroscopic data (vide infra), the CO ligand
was approximated by a nearly isoelectronic chloride group in
the rigid body to maintain space group symmetry and simplify
complexes shown in Scheme 1.40 All of the new complexes
a
Scheme 1. Synthesis of PNNNP-Ru Metallolinkers
the Rietveld refinement. The refinement converged to Rwp
=
14.03 with final lattice parameters of a = 31.9437(6) Å and c =
15.8051(3) Å. The refined structure of 1 shows small trigonal
and larger hexagonal channels along the c axis (Figure 1c). The
large channels have a maximum diameter of ∼15 Å but are
constricted to a minimum diameter of ∼6 Å by the inward-
facing arene groups of the pincer complexes. The mean plane
of the pincer arene groups is oriented perpendicular to the
crystallographic ab plane. The [cis-L-RuCl2(CO)]4− linkers
and OAc groups of the [Zr6O4(OH)4(OAc)4]8+ metal clusters
face inward to the smaller trigonal channels, restricting their
diameter to ∼6 Å.
a
Reagents and conditions: (i) RuCl(H)(CO)(PPh3)3, THF, 70 °C,
16 h; (ii) NaO2CCF3, THF/CHCl3, room temperature, 2 h; (iii)
CF3 CO2 H, CH2 Cl2 , room temperature, 16 h; (iv)
RuCl2(CO)3(THF), 1,4-dioxane, 100 °C, 16 h; (v) Me3NO,
CH2Cl2, room temperature, 1 h.
have been characterized by multinuclear NMR and IR
spectroscopy and elemental analysis (Figures S1−S20). The
cis stereochemistry of [tBu4L-RuCl(CO)2]Cl and [H4L-RuCl-
(CO)2]TFA is established by the presence of two distinct sets
1
of aromatic H NMR resonances corresponding to inequiva-
Solution- and solid-state NMR spectroscopy has been used
to determine the composition of 1−3. The solid-state 31P
NMR spectrum of 1 shows a single major resonance centered
lent benzoate groups as well as two carbonyl stretching bands
of equal intensity appearing at 2064 and 2010 cm−1 in the
B
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Figure 2. Solid-state 31P NMR spectra of 1, 2, and 3. Asterisks (*)
mark residual spinning side bands.
The solid-state and acid-digested, solution-state 31P NMR
spectra of 2 both exhibit a major resonance at 82 ppm, which is
consistent with the presence of cis-[H4(L-RuCl(CO)2)]+
pincer complexes (81.8 ppm in DMSO-d6). The solid-state
1
13C NMR spectrum of the MOF and the H NMR spectrum
after acid digestion show all expected resonances for [H4(L-
RuCl(CO)2)]+ as well as HCO2H arising from
[Zr6O4(OH)4(O2CH)4]8+ SBUs (Figures S27e and S28).
The ATR-IR spectrum of 2 contains two strong ν(CO)
bands of similar intensity at 2070 and 2016 cm−1, indicating
that the two carbonyl ligands remain in a cis arrangement
(Figure S41).
Figure 1. (a) XRPD patterns (Cu Kα radiation, λ = 1.5418 Å) for 1−
3. (b) Rietveld refinement profile of 1 from SXPD data (λ = 0.414536
Å). (c) Framework structure of 1. (d) Structure of the D4h
[Zr6O4(OH)4(OAc)4]8+ secondary building units.
at 68 ppm, and no signal attributable to the PPh3 ligand was
observed (Figure 2). This finding is corroborated by solution-
state NMR analysis of a CsF-digested sample, which shows one
major singlet resonance at 70.6 ppm in the 31P NMR spectrum
and a set of signals in the 1H NMR spectrum that are
consistent with a single PNNNP-Ru complex exhibiting Cs
symmetry (Figures S22 and S23). The ATR-IR spectrum of
1 shows a broad Ru−CO stretching band at 1982 cm−1 (Figure
S41). Overall, the spectroscopic data are consistent with cis-[L-
RuCl2(CO)]4− linkers resulting from substitution of the Ph3P
and TFA ancillary ligands in [H4L-Ru(TFA)(CO)(PPh3)]
with Cl− during the solvothermal assembly. Accordingly, 31P
NMR analysis of the supernatant solution from the
solvothermal synthesis shows the presence of Ph3PO (Figure
The solid-state 31P NMR spectrum of 3 shows two major
resonances at 68 and 92 ppm, corresponding to a ∼1:2 mixture
of cis- and trans-[L-RuCl2(CO)]4− linkers in the MOF. The
minor resonance at 82 ppm matches that observed for 2,
indicating that 3 contains a small amount (<10%) of cis-[L-
RuCl(CO)2]3− metallolinkers. This species is likely generated
from CO produced as a result of DMF decomposition. Greater
amounts of cis-[L-RuCl(CO)2]3− were observed when the
solvothermal synthesis of 3 was carried out with longer
reaction times or with HCO2H instead of CH3CO2H as the
modulator (Figure S32), but its formation could be almost
completely inhibited by limiting the solvothermal reaction
times to 20 h. Under these conditions, the acid-digested 31P
NMR spectrum of 3 shows only resonances attributable to cis-
and trans-[L-RuCl2(CO)]4− complexes at 73.9 and 90.9 ppm,
respectively, and a single ν(CO) band at 1988 cm−1 in the
ATR-IR spectrum (Figures S22 and S41).
1
S26). The H NMR spectrum of a CsF-digested sample of 1
also shows that CH3CO2H is present in a ∼2:1 ratio with
respect to the PNNNP-RuCl2(CO) metallolinkers, supporting
the presence of [Zr6O4(OH)4(OAc)4]8+ secondary building
units (SBUs) in the MOF (Figure S23); the bound acetate is
also detected in the 13C NMR spectrum of the MOF (Figure
S27d).
Thermogravimetric analyses (TGA) of MeOH-exchanged
samples of 1 and 3 show the loss of guest solvent molecules
(∼20 wt %) up to 100 °C and the onset of framework
decomposition at 300−350 °C (Figures S33 and S34). XRPD
C
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analysis revealed that 2 was unstable to drying after MeOH
solvent exchange (Figure S36). As a result, THF was used for
1
solvent exchange, although H NMR analysis showed that it
could not completely remove DMF guest solvent molecules.
Subsequent TGA analysis of THF-exchanged 2 shows the loss
of guest solvent molecules (∼30 wt %) up to 200 °C and
framework decomposition above 350 °C (Figure S35). N2
adsorption isotherms (77 K) measured for samples of 1−3
after solvent exchange and desolvation by heating at 100 °C
and 10−4 Torr for 16 h gave calculated BET surface areas of
928, 334, and 728 m2 g−1, respectively (Figures S37−S39).
Notably, the BET surface area of 1 is only slightly lower than
the theoretical accessible surface area (1019 m2 g−1) calculated
using the structure model obtained from Rietveld refinement.63
2 showed a modest increase in N2 uptake and BET surface area
(451 m2 g−1) when the MOF was activated by lyophilization
with benzene. However, XRPD analysis shows that, while 1
and 3 remain crystalline after activation, 2 experiences a loss of
crystallinity (Figure S40). The poor structural stability of 2
may be due to a greater number of defects resulting from the
use of HCO2H as a modulator.64 The ATR-IR spectra of
activated samples of 2 still show the presence of two ν(CO)
bands, indicating that desolvation does not lead to significant
1
loss of Ru-coordinated CO ligands (Figure S42). H and 31P
NMR analyses of acid-digested samples of desolvated 2
confirm that cis-[L-RuCl(CO)2]3− is the major linker
component with only a small amount of [L-RuCl2(CO)]4−
species resulting from CO ligand loss (Figures S29 and S30).
Postsynthetic Activation and Catalytic Hydrosilyla-
tion Studies. Deprotonation of the methylene or amide linker
groups of Ru diphosphine pincer complexes has proven to be a
valuable strategy for precatalyst activation.58−60,65 The
deprotonation step often eliminates coordinated halide ligands,
increases the ligand donor strength of the central pyridine, and
can switch on metal−ligand cooperativity in subsequent steps
of a catalytic cycle. With this precedent in mind, we
investigated a sequence of postsynthetic deprotonation and
CO ligand removal steps as a means of activating 1−3 for
further reactivity and catalytic studies.
Figure 3. (a) ATR-IR spectra for 2, 2-a, and 2-b. (b) XRPD patterns
(Cu Kα radiation, λ = 1.5418 Å) for 2-b before catalysis and after
catalytic run 4.
analogue, cis-[tBu4L-RuCl(CO)2]Cl, with KOtBu results in a
similar shift in the CO stretching bands (Figure S48). The Ru
sites in 2-a remain coordinatively saturated owing to the
presence of the two strongly bound CO ligands. Consequently,
the MOF was treated with Me3NO to generate 2-b. The loss of
a CO ligand was confirmed by the appearance of a single broad
CO stretching band at 1955 cm−1 (Figure 3a).
The MOFs were treated with KOtBu (2 equiv per Ru) in
THF to induce deprotonation of the NH linker groups
(Scheme 3). Subsequent XRPD analysis revealed reflections
Catalytic hydrosilylation of carbonyls provides a mild and
economical route for generating silane-protected alcohols.
Homogeneous organometallic complexes, including those
supported by diphosphine pincer ligands, have been reported
to efficiently catalyze the hydrosilylation of carbonyl
groups.67−71 However, relatively few MOFs have been
reported to catalyze hydrosilylation reactions.72−75 Hydro-
silylation of carbonyls with a well-defined and recyclable
catalyst presents an attractive approach to the hydrogenation
of carbonyl substrates. Consequently, we set out to examine
the PNNNP-Ru MOFs as catalysts for the hydrosilylation of
aldehydes and ketones. Initial catalytic reactions were carried
out at 100 °C in 1,4-dioxane with benzaldehyde and Et3SiH as
substrates and 5 mol % catalyst loading (based on Ru).
Product yields were determined by 1H NMR and/or GC-MS/
FID analysis with hexamethylbenzene as an internal standard.
The unactivated MOFs 1−3 afforded less than 6% yield of
benzyloxytriethylsilane under these conditions (Table 1,
entries 1, 3, and 6).
a
Scheme 3. Deprotonation and CO Removal Reactions
a
Reagents and conditions: (i) KOtBu, THF, room temperature, 16 h;
(ii) Me3NO, THF/CH2Cl2, room temperature, 16 h.
attributable to crystalline KCl in 2-a, but not in the base-
treated samples of 1 and 3 (Figure 3b and Figures S45−S47).
The difference in reactivity observed for 2 is presumably due to
the presence of outer-sphere Cl− ions that are more easily
released than the inner-sphere halides found in 1 and 3. The
ATR-IR spectrum of 2-a shows that the CO stretching bands
are shifted to lower energy by ∼20 cm−1 in comparison to
those observed for 2 (Figure 3a). This redshift is consistent
with weakening of CO bonds due to an increase in electron
density at the Ru center.66 The reaction of the homogeneous
In contrast, 2-b proved to be an effective catalyst, providing
the silyl ether product in 94% yield after 12 h (entry 5). The
deprotonated MOF 2-a (10% yield) and a sample of 2 treated
with Me3NO (6% yield, Figure S54) showed little activity for
D
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a
MOF (Figures S71 and S72). 2-b also shows unexpectedly low
catalytic activity with acetophenone as a substrate.
Table 1. Catalytic Hydrosilylation of Benzaldehyde
The homogeneous complexes [tBu4L-RuCl(CO)2]Cl and
tBu4L-RuCl2(CO) were found to be inactive for the catalytic
hydrosilylation reaction (Table 1, entries 8 and 9), and a
homogeneous analogue of 2-b prepared by treating [tBu4L-
RuCl(CO)2]Cl with KOtBu and Me3NO showed only a slight
increase in catalytic activity (entry 10). Interestingly, NMR
analysis of [tBu4L-RuCl(CO)2]Cl after the deprotonation and
CO ligand removal steps showed a mixture of species that
could not be clearly identified but give rise to signals
characteristic of PNNNP-Ru complexes. The ATR-IR spectrum
of the activated homogeneous complex also shows a single
broad CO stretching band at 1951 cm−1, confirming formation
of monocarbonyl species resembling that observed in 2-b
(Figure S48). Attempts to isolate and further characterize these
species were unsuccessful. 31P NMR analysis of the
homogeneous reaction mixture after catalysis shows a similarly
complex mixture of species, but no signals indicative of pincer
decomposition were observed. Although it is not presently
clear why the homogeneous PNNNP-Ru complexes are inactive
for catalytic hydrosilylation, their immobilization as linkers in
2-b proves to be beneficial for stabilizing catalytically active
species.
b
entry
catalyst
yield (%)
1
2
3
4
5
6
7
8
1
<5
<5
<5
10
94
6
<5
<5
<5
10
33
95
72
1-KOtBu
2
2-a
2-b
3
3-KOtBu
[tBu4L-RuCl(CO)2]Cl
tBu4L-RuCl2(CO)
[tBu4L-RuCl(CO)2]Cl/KOtBu/Me3NO
2-b (run 2)
9
c
10
11
d
12
d
2-b (run 3)
2-b (run 4)
13
a
Reaction conditions: substrate (0.2 mmol), catalyst (0.01 mmol),
b
silane (0.4 mmol), dioxane (1 mL), 12 h, 100 °C. Yields were
determined by 1H NMR spectroscopy with respect to an internal
c
standard (hexamethylbenzene). tBu4L-RuCl(CO)2]Cl treated with
d
KOtBu followed by Me3NO. The catalyst was regenerated by
treatment with Me3NO.
CONCLUSIONS
■
In summary, we have described the synthesis, characterization,
and reactivity of a series of three isostructural Zr MOFs
assembled from PNNNP-Ru metallolinkers. Among these
MOFs, only 2 could be readily activated to generate a
heterogeneous catalyst for the hydrosilylation of aryl
aldehydes. The difference in reactivity among the series is
rationalized by the presence of outer-sphere Cl− ions in 2 that
are more readily eliminated than the coordinated Cl ligands in
1 and 3. Subsequent CO-ligand removal from 2-a generates a
coordinatively unsaturated PNNNP-Ru species capable of
catalyzing hydrosilylation reactions. These results demonstrate
the importance of the rational and diligent activation of MOF
precatalysts. Moreover, the disparate reactivity of 2 and its
homogeneous analogue point to a beneficial site isolation
effect. Ongoing studies are focused on elucidating the origin of
this effect and expanding the catalytic applications of MOF-
immobilized PNNNP-Ru pincer complexes.
the reaction. These results support catalysis occurring at the
activated Ru sites rather than Lewis acidic Zr sites and
highlight the importance of the deprotonation and CO ligand
removal steps for precatalyst activation. Recent work by Huang
and co-workers suggests that a deprotonated PNNNP-NiH
complex may act as a basic “organocatalyst” in hydrosilylation
reactions without direct involvement of the Ni center.76,77
While we cannot rule out the possibility of a related
mechanism for 2-b, the need for CO ligand removal implies
the requirement of a coordinatively unsaturated Ru center. The
catalytic efficiency of 2-b dropped considerably (33% yield)
upon attempted recycling of the catalyst. The ATR-IR
spectrum of the MOF after the second run showed the
appearance of new CO stretching bands at 2050 and 1980
cm−1, consistent with the formation of cis-[L-RuCl(CO)2]3−
pincer species (Figure S49). The appearance of cis-[L-
RuCl(CO)2]3− can be attributed to off-cycle decarbonylation
of benzaldehyde and, on the basis of the poor catalytic activity
of 2 and 2-a, should lead to catalyst deactivation. Notably, 2-b
was not observed to catalyze decarbonylation of benzaldehyde
at elevated temperatures or in the presence of Me3NO as a CO
scavenger. Nevertheless, we found that the recovered MOF
catalyst could be reactivated for subsequent hydrosilylation
reactions upon treatment with Me3NO. The ensuing catalytic
run (entry 12) showed nearly complete recovery of the
catalytic activity, although a modest drop in activity was
observed in subsequent recycling steps.
EXPERIMENTAL SECTION
General Considerations. Bu4(L) and RuHCl(CO)(PPh3)3
■
40
78
t
were prepared following literature procedures. THF and 1,4-dioxane
were degassed by sparging with ultrahigh-purity argon and dried via
passage through columns of drying agents using a solvent purification
system from Pure Process Technologies. All other solvents and
reagents were purchased from commercial suppliers and used as
received. Routine X-ray powder diffraction (XRPD) patterns for
phase identification were collected using a Rigaku Miniflex 600
diffractometer with nickel-filtered Cu Kα radiation (λ = 1.5418 Å).
High-resolution synchrotron X-ray powder diffraction (SXPD) data
were collected at 295 K using beamline 11-BM at the Advanced
Photon Source (APS, Argonne National Laboratory, Argonne, IL)
with an average wavelength of 0.414536 Å. Rietveld refinement was
carried out with TOPAS-Academic.79 ATR-IR spectra were measured
using a Bruker Alpha II spectrometer with a diamond ATR accessory.
N2 adsorption isotherms (77 K, liquid nitrogen bath) were measured
using a Micromeritics 3Flex Surface Characterization Analyzer. Prior
to analysis, samples (100−200 mg) were heated under reduced
pressure until the outgas rate was less than 2 mTorr/min. GC-MS
Notably, 2-b remains crystalline after regenerating and
recycling the catalyst (Figure 3b). Moreover, no additional
substrate conversion was observed in the reaction supernatant
after hot filtration, supporting the heterogeneous nature of the
catalysis (Figure S62). 2-b demonstrates good catalytic activity
for hydrosilylation of a range of benzaldehyde derivatives
(Table S3). However, <10% yield of hydrosilylated product
was obtained with a large substrate, 3,5-dibenzyloxybenzalde-
hyde, indicating substrate transport limitations within the
E
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analysis was performed using an Agilent 7890B GC system equipped
with the HP-5 Ultra Inert column (30 m, 0.25 mm, 0.25 μm) and an
FID detector. For MS detection an electron ionization system was
used with an ionization energy of 70 eV. Elemental analyses (C, H, N)
were performed by Robertson Microlit Laboratories (Ledgewood,
NJ).
8H, 3JH−H = 6.00 Hz, benzoate Ar-H), 7.39 (br, 3H, PPh3 Ar-H), 7.73
3
3
(t, 1H, JH−H = 8.23 Hz, pyridine Ar-H), 7.79 (d, 4H, JH−H = 7.86
3
Hz, benzoate Ar-H), 7.95 (d, 4H, JH−H = 7.86 Hz, benzoate Ar-H).
31P{1H} NMR (162 MHz, DMSO-d6): δ 27.6 (t, 1P, 2JP−P = 24.3 Hz),
2
78.1 (d, 2P, JP−P = 22.68 Hz). ATR-IR: ν(CO) 1982 cm−1. Anal.
Calcd for [H4L-Ru(TFA)(CO)(PPh3)]TFA, C56H40F6N3O13P3Ru: C,
52.92; H, 3.17; N, 3.31. Found: C, 53.44; H, 3.47; N, 3.42.
Solution-state NMR spectra were measured using either a Varian
1
Inova or Bruker 400 MHz spectrometer. For H and 13C{1H} NMR
Synthesis of 1. A 20 mL scintillation vial was charged with ZrCl4
(16 mg, 0.070 mmol), DMF (4 mL), and glacial acetic acid (1.5 mL).
The mixture was sonicated for 20 min until it became a clear colorless
solution. The solution was then transferred to a vial containing a
solution of [H4L-Ru(TFA)(CO)(PPh3)]TFA (30 mg, 0.024 mmol)
in DMF (2 mL). The vial was sealed with a Teflon-lined screw-top
cap (Qorpak CAP-00554) and heated to 120 °C in a programmable
oven for 16 h. After the reaction mixture was cooled to room
temperature, the solid was collected by centrifugation, washed with
DMF (3 × 10 mL), and soaked in MeOH (4 × 10 mL) for a total of
24 h. 1 was obtained as a nearly colorless microcrystalline powder (40
mg) after drying in vacuo. 31P{1H} NMR (162 MHz, CsF/DMSO-d6/
D2O): δ 70.8 (s, 2P), 28.5 (broad, minor impurity). On the basis of
elemental analysis and NMR spectroscopic data obtained for 1 after
MeOH solvent exchange and activation (Figures S23−S25), the
empirical formula is best given as Zr6O4(OH)4(CH3CO2)2.8(OH)0.4-
(L-RuCl2(CO))2(Ar2PO2Me)0.4(MeOH)0.15(DMF)0.5 (Ar = p-C6H4-
CO2). The presence of Ar2PO2Me in 1 is supported by the minor
resonance observed in solid- and solution-state 31P NMR spectra
around 20 ppm. In addition, the CsF-digested 1H NMR spectrum of 1
after activation shows a set of resonances in the aromatic region
attributed to the decomposed species. Anal. Calcd for 1, Zr6
O4OH4(CH3CO2)2.8(OH)0.4(C33H21N3O8P2RuCl2(CO))2-
(C14H9O6P)0.4(MeOH)0.15(DMF)0.5: C, 35.88; H, 2.38; N, 3.35.
Found: C, 36.09; H, 2.88; N, 3.23.
spectra, the solvent resonance was referenced as an internal standard.
For 31P NMR spectra, 85% H3PO4 was used as an external standard
1
(0 ppm). Solvent-suppressed H NMR spectra were collected using
180° water selective excitation sculpting with default parameters and
pulse shapes.80 Solid-state NMR experiments were performed using a
Bruker DSX-400 spectrometer at a resonance frequency of 162 MHz
for 31P with a magic-angle spinning (MAS) probe in double-resonance
mode. Samples were packed into 4 mm rotors with Kel-F 22 μL
HRMAS inserts. Experiments were carried out at spinning frequencies
1
of 10−13.5 kHz. Typical 31P and H 90° pulse lengths were 4 and 6
μs, respectively. 31P NMR spectra were obtained after composite-
1
pulse multiple cross-polarization from H, with a recycle delay of 1 s
and 10 blocks of 1.1 ms 90−100% ramp cross-polarization separated
81
1
by 0.5 s H repolarization periods. Four-pulse total suppression of
sidebands (TOSS) was used to obtain spectra almost without
spinning sidebands.82 Two-pulse phase modulation 1H decoupling
was applied during detection.83 31P spectra were externally referenced
to the upfield resonance of calcium hydroxyapatite (National Institute
of Standards and Technology) at 2.73 ppm; this corresponds to the
85% H3PO4 scale.
t
Synthesis of [tBu4L-RuH(CO)(PPh3)]Cl. A solution of Bu4(L)
(0.77 g, 0.88 mmol) in THF (3 mL) was added dropwise to a
suspension of RuHCl(CO)(PPh3)3 (0.84 g, 0.88 mmol) in THF (20
mL). The reaction was heated at 60 °C overnight with vigorous
stirring, resulting in formation of a white precipitate. After it was
cooled to room temperature, the solid was collected by filtration,
washed with Et2O (3 × 10 mL), and dried in vacuo to afford a white
powder (0.84 g, 73%). 1H NMR (400 MHz, DMSO-d6): δ −7.24 (dt,
1H, 2JP−H = 86.88 Hz, 26.23 Hz, Ru-H), 1.53 (s, 36H, tBu), 6.26 (d,
2H, 3JH−H = 8.26 Hz, pyridine Ar-H), 6.98 (m, 15H, PPh3 Ar-H), 7.28
Synthesis of RuCl2(CO)3(THF). RuCl2(CO)3(THF) was pre-
pared by modification of a procedure reported for the synthesis of
[RuCl2(CO)2]n.84 A 200 mL Schlenk flask was charged with RuCl3·
3H2O (2 g, 0.76 mmol) and formic acid (67 mL). The flask was fitted
with a reflux condenser and heated in an oil bath at 107 °C for 14 h
under a nitrogen atmosphere. It is critical that the reaction be carried
out at the specified temperature to obtain the desired product, as
higher or lower temperatures lead to mixtures of unidentified
products. After the mixture was cooled to room temperature, the
excess formic acid was evaporated from the faint yellow solution
under reduced pressure, and the resulting solid was washed with
CH2Cl2 (3 × 10 mL) to afford a white powder (1.75 g). The white
solid was identified as the formic acid adduct RuCl2(CO)3(HCO2H)
on the basis of the ATR-IR spectrum (ν(CO) 2146 and 2066 cm−1,
3
(m, 5H, pyridine and benzoate Ar-H), 7.60 (d, 4H, JH−H = 8.15 Hz,
benzoate Ar-H), 8.06 (m, 8H, benzoate Ar-H), 9.94 (br, 2H, NH).
2
31P{1H} NMR (162 MHz, DMSO-d6): δ 39.8 (t, 1P, JP−P = 18.69
2
Hz), 99.9 (d, 2P, JP−P = 19.31 Hz). ATR-IR: ν(CO) 1940 cm−1.
Anal. Calcd for [tBu4(LRuH)]Cl·H2O, C68H75ClN3O10P3Ru: C,
61.70; H, 5.71; N, 3.17. Found: C, 61.30; H, 5.47; N, 3.13.
Synthesis of [tBu4L-RuH(CO)(PPh3)]TFA. A solution of
NaO2CCF3 (0.14 g, 0.96 mmol) in THF (5 mL) was added to a
solution of [tBu4L-RuH(CO)(PPh3)]Cl (0.92 g, 0.70 mmol) in
CHCl3 (5 mL) and stirred at room temperature for 2 h. The volatiles
were removed under reduced pressure, and the solid was extracted
into CHCl3 (5 mL) with sonication. The resulting suspension was
filtered through a pad of Celite to ensure complete removal of NaCl.
After the solvent was removed in vacuo, the product was obtained as a
gray powder (0.90 g, 93%). 1H NMR (400 MHz, DMSO-d6): δ −7.35
(dt, 1H, 2JP−H = 86.57 Hz, 23.35 Hz, Ru-H), 1.52 (s, 36H, tBu), 6.23
(d, 2H, 3JH−H = 7.24 Hz, pyridine Ar-H), 6.99 (m, 15H, PPh3 Ar-H),
7.28 (br, 5H, pyridine and benzoate Ar-H), 7.60 (d, 4H, 3JH−H = 7.63
ν(CO2) 1735 and 1141 cm−1 ν(OH) 3164 cm−1). Recrystallization
,
from hot THF (5 mL) gave the THF adduct RuCl2(CO)3(THF) as a
white low-density solid (1.5 g). ATR-IR: ν(CO) 2137 and 2054 cm−1,
ν(THF) 1023 and 874 cm−1. ATR-IR spectra of these products are
provided in Figure S21.
Synthesis of cis-[tBu4L-RuCl(CO)2]Cl. A solution of
RuCl2(CO)3(THF) (0.15 g, 0.46 mmol) in 1,4-dioxane (5 mL) was
added to a solution of tBu4(L) (0.41 g, 0.47 mmol) in 1,4-dioxane (5
mL) and stirred at 100 °C for 16 h. The reaction mixture was cooled
to room temperature, and the solid was collected by filtration and
washed with 1,4-dioxane (2 × 10 mL) and pentane (3 × 10 mL). The
solid was dried in vacuo to afford a colorless powder (0.33 g, 65%).
1H NMR (400 MHz, DMSO-d6): δ 1.52 (s, 36H, tBu), 6.90 (d, 2H,
3JH−H = 8.87 Hz, pyridine Ar-H), 7.86 (m, 5H, pyridine and benzoate
Ar-H), 8.06 (m, 12H, benzoate Ar-H), 11.04 (s, 2H, NH). 31P{1H}
NMR (162 MHz, DMSO-d6): δ 81.3 (s, 2P). ATR-IR: ν(CO) 2062
Hz, benzoate Ar-H), 8.06 (br, 8H, benzoate Ar-H), 9.90 (br, 2H,
2
NH). 31P{1H} NMR (162 MHz, DMSO-d6): δ 39.8 (t, 1P, JP−P
=
2
19.75 Hz), 99.8 (d, 2P, JP−P = 19.26 Hz). ATR-IR: ν(CO) 1945
cm−1.
Synthesis of [H4L-Ru(TFA)(CO)(PPh3)]TFA. A 20 mL scintilla-
tion vial was charged with [tBu4L-RuH(CO)(PPh3)]TFA (0.90 g,
0.60 mmol), CH2Cl2 (3 mL), and CF3CO2H (1 mL) and stirred at
room temperature for 16 h. The solvent was then removed using a
rotary evaporator, and the resulting brown solid was dissolved in a
minimal amount of methanol (∼2 mL). The product was precipitated
with Et2O (∼15 mL), collected by filtration, and washed with Et2O (3
× 10 mL). The product was obtained as a white powder (0.66 g, 87%)
after drying in vacuo. 1H NMR (400 MHz, DMSO-d6): δ 6.67 (d, 2H,
3JH−H= 7.76 Hz, pyridine Ar-H), 7.08 (m, 12H, PPh3 Ar-H), 7.24 (t,
and 2009 cm−1
.
Anal. Calcd for [tBu4L-RuCl(CO)2]Cl,
C51H57Cl2RuN3O10P2: C, 55.39; H, 5.20; N, 3.80. Found: C, 55.28;
H, 5.17; N, 3.76.
Synthesis of cis-[H4L-RuCl(CO)2]TFA. A 20 mL scintillation vial
was charged with [tBu4L-RuCl(CO)2]Cl (0.25 g, 0.23 mmol), CH2Cl2
(3 mL), and CF3CO2H (1 mL). The vial was sealed, and the solution
was stirred at room temperature for 16 h. Deionized water (5 mL)
was added to the reaction mixture, resulting in formation of a white
F
DOI: 10.1021/acs.organomet.9b00482
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
precipitate. The product was collected by filtration, washed with
deionized water (2 × 10 mL) and CHCl3 (3 × 10 mL), and dried
Synthesis of 3. A 20 mL scintillation vial was charged with ZrCl4
(49 mg, 0.21 mmol), DMF (8 mL), and glacial acetic acid (3 mL).
The mixture was sonicated for 20 min to afford a colorless solution.
The solution was then added to a solution of cis-/trans-H4L-
RuCl2(CO) (60 mg, 0.070 mmol) in DMF (4 mL) in a 20 mL
scintillation vial. The vial was sealed with a Teflon-lined screw-top cap
(Qorpak CAP-00554) and heated to 120 °C in a programmable oven
for 20 h. After the reaction mixture was cooled to room temperature,
the solid was collected by centrifugation, washed with DMF (3 × 10
mL), and soaked in MeOH (4 × 10 mL) for a total of 24 h. 3 was
obtained as a colorless microcrystalline powder (61 mg) after drying
in vacuo. 31P{1H} NMR (162 MHz, CF3CO2H/DMSO-d6): δ 90.9 (s,
2P, trans isomer), 73.9 (s, 2p, cis isomer). ATR-IR: v(CO) 1988
cm−1. On the basis of elemental analysis and NMR spectroscopic data
obtained for 3 after MeOH solvent exchange and activation, the
empirical formula is best given as Zr6O4(OH4)(CH3CO2)4(L-
RuCl2(CO))2(H2O)2(MeOH). Anal. Calcd for 3; Zr6O4(OH)4-
(CH3CO2)4(C33H21N3O8P2RuCl2(CO))2(H2O)2(MeOH)2: C,
34.51; H, 2.60; N; 3.10. Found: C, 33.64; H, 2.87; N, 3.22.
Synthesis of 2-a and 2-b. A 20 mL scintillation was charged with
2 (0.154 g, 0.11 mmol of Ru), and a solution of KOtBu in THF was
added (0.1 M, 2.2 mL, 0.22 mmol). An immediate color change to
yellow was observed upon KOtBu addition, and the resulting mixture
was gently stirred at room temperature for 16 h. The solid was
collected via centrifugation and washed with THF (3 × 10 mL) to
afford 2-a. 2-a was then treated with a solution of Me3NO in CH2Cl2
(0.1 M, 2.2 mL, 0.22 mmol) at room temperature for 16 h to generate
2-b. The solid was collected via centrifugation, washed with THF (4
× 10 mL), and dried in vacuo to afford a yellow microcrystalline
powder (128 mg).
General Procedure for Hydrosilylation Reactions. In a N2-
filled glovebox, a 1 dram screw-top vial was charged with the catalyst
(5 mol % based on Ru), 1,4-dioxane (1 mL), Et3SiH (0.4 mmol),
substrate (0.2 mmol), and hexamethylbenzene as an internal standard
(0.025 mmol). The vial was sealed with a Teflon-lined screw-top cap,
and the reaction mixture was heated at 100 °C for 12 h. The products
of the reaction were characterized by 1H NMR and GC-MS/FID, and
yields were determined by integration of 1H NMR spectra with
respect to the internal standard. For recycling experiments without
regeneration, the catalyst was isolated from the reaction mixture via
centrifugation, washed with 1,4-dioxane (3 × 2 mL), and resubjected
to the catalytic conditions. Regeneration and recycling was carried out
by washing the solid catalyst with 1,4-dioxane (3 × 2 mL) and then
treating the solid with a solution of Me3NO in CH2Cl2 as described
above.
1
under reduced pressure to yield a white powder (0.21 g, 97%). H
3
NMR (400 MHz, DMSO-d6): δ 6.83 (d, 2H, JH−H = 8.25 Hz,
pyridine Ar-H), 7.84 (m, 5H, pyridine and benzoate Ar-H), 7.99 (m,
3
4H, benzoate Ar-H), 8.09 (d, 4H, JH−H = 8.00 Hz, benzoate Ar-H),
8.14 (d, 4H, 3JH−H = 7.87, benzoate Ar-H), 10.72 (s, 2H, NH), 13.47
(br, 4H, CO2H). 31P{1H} NMR (162 MHz, DMSO-d6): δ 81.8 (s,
2P). 19F NMR (376 MHz, DMSO-d6): δ −74.0 (s, 3F). ATR-IR:
ν(CO) 2077 and 2022 cm−1. Anal. Calcd for [H4L-RuCl(CO)2]TFA·
H2O, C37H27ClF3N3O13P2Ru: C, 45.48; H, 2.79; N, 4.30. Found: C,
45.28; H, 2.84; N, 4.32.
Synthesis of 2. A 20 mL scintillation vial was charged with ZrCl4
(44 mg, 0.19 mmol), DMF (8 mL), and formic acid (3 mL). The
mixture was sonicated for 20 min to afford a colorless solution. The
solution was then added to a solution of [H4L-RuCl(CO)2]TFA (60
mg, 0.062 mmol) in DMF (4 mL) in a 20 mL scintillation vial. The
vial was sealed with a Teflon-lined screw-top cap (Qorpak CAP-
00554) and heated to 120 °C in a programmable oven for 18 h. After
the mixture was cooled to room temperature, the solid was collected
by centrifugation, washed with DMF (3 × 10 mL), and soaked in
THF (4 × 10 mL) for a total of 24 h. 2 was obtained as a nearly
colorless microcrystalline powder (77 mg) after drying in vacuo.
31P{1H} NMR (162 MHz, CF3CO2H/DMSO-d6): δ 82.4 (s, 2P).
ATR-IR: ν(CO) 2067 and 2013 cm−1. On the basis of elemental
analysis and NMR spectroscopic data obtained for 2 after THF
solvent exchange and activation, the empirical formula is best given as
Zr6O4(OH4)(HCO2)4(L-RuCl(CO)2)2Cl2(DMF)2(H2O)2. Anal.
Calcd for 2, Zr6O4OH4(HCO2)4(C33H21N3O8P2RuCl(CO)2)2Cl2-
(H2O)2(DMF)2: C, 34.36; H, 2.45; N; 4.01. Found: C, 32.90; H,
2.85; N, 4.01.
Synthesis of cis-/trans-tBu4L-RuCl2(CO). A solution of Me3NO
in CH2Cl2 (0.10 M, 3.8 mL, 0.38 mmol) was added to a solution of
[tBu4L-RuCl(CO)2]Cl (0.42 g, 0.38 mmol) in CH2Cl2 (5 mL) in a 20
mL scintillation vial, and the resulting mixture was stirred at room
temperature for 1 h. The solution turned yellow immediately upon
addition of Me3NO. The volatiles were removed under reduced
t
pressure to yield a yellow powder (0.39 g, 96%). Bu4L-RuCl2(CO)
was obtained as a mixture of cis and trans isomers (cis:trans ratio ≈
1:2). 1H NMR (400 MHz, DMSO-d6): δ 1.51 (s, 36H, tBu), 6.72 (d,
2H, 3JH−H = 8.29 Hz, pyridine Ar-H, cis isomer), 6.75 (d, 2H, 3JH−H
=
3
8.10 Hz, pyridine Ar-H, trans isomer), 7.59 (t, 1H, JH−H = 8.14 Hz,
pyridine Ar-H, cis isomer), 7.66 (t, 1H, 3JH−H = 8.15 Hz, pyridine Ar-
3
3
H, trans isomer), 7.85 (dd, 8H, JH−H = 11.79 Hz, JP−H = 6.30 Hz,
benzoate Ar-H, trans isomer), 7.93 (d, 8H, 3JH−H = 8.73 Hz, benzoate
Ar-H, trans isomer), 7.97 (br, 8H, benzoate Ar-H, cis isomer), 8.03−
8.22 (8H, benzoate Ar-H, cis isomer), 10.14 (s, 2H, NH, trans
isomer), 10.42 (s, 2H, NH, cis isomer). 31P{1H} NMR (162 MHz,
DMSO-d6): δ 71.3 (s, 2P, cis isomer), 90.2 (s, 2P, trans isomer).
ATR-IR: ν(CO) 1964 cm−1.
ASSOCIATED CONTENT
■
S
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.9b00482.
Synthesis of cis-/trans-H4L-RuCl2(CO). A 20 mL scintillation
vial was charged with tBu4L-RuCl2(CO) (0.35 g, 0.32 mmol), CH2Cl2
(3 mL), CF3CO2H (1 mL), and concentrated HCl (0.1 mL). The vial
was sealed and stirred at room temperature for 16 h. Et2O (10 mL)
was added to the reaction solution, resulting in a white precipitate.
The solid was collected by filtration, washed with Et2O (3 × 10 mL),
and dried in vacuo to afford the product as a light yellow powder
(0.25 g, 91%). 1H NMR (400 MHz, DMSO-d6): δ 6.65 (d, 2H, 3JH−H
Spectroscopic (NMR, IR), GC-MS, XRPD, TGA, and
N2 gas adsorption data, details of the Rietveld refine-
ment of 2, and additional data for catalytic hydro-
silylation of benzaldehyde derivatives (PDF)
3
= 8.02 Hz, pyridine Ar-H, cis isomer), 6.70 (d, 2H, JH−H = 8.01 Hz,
3
AUTHOR INFORMATION
pyridine Ar-H, trans isomer), 7.59 (t, 1H, JH−H = 7.84 Hz, pyridine
■
3
Ar-H, cis isomer), 7.66 (t, 1H, JH−H = 8.19 Hz, pyridine Ar-H, trans
Corresponding Author
*E-mail for C.R.W.: wade.521@osu.edu.
3
3
isomer), 7.83 (dd, 8H, JH−H = 12.63 Hz, JP−H = 6.68 Hz, benzoate
Ar-H, trans isomer), 7.93 (dd, 4H, 3JH−H = 13.56 Hz, 3JP−H = 6.67 Hz,
benzoate Ar-H, cis isomer), 7.98 (d, 8H, JH−H= 8.23 Hz, benzoate
3
ORCID
3
Ar-H, trans), 8.03 (d, 4H, JH−H = 8.01 Hz, benzoate Ar-H, cis-
Abebu A. Kassie: 0000-0002-0989-0084
Matthew B. Gray: 0000-0002-9526-4732
Klaus Schmidt-Rohr: 0000-0002-3188-4828
Patrick M. Woodward: 0000-0002-3441-2148
Casey R. Wade: 0000-0002-7044-9749
3
3
isomer), 8.18 (dd, 4H, JH−H = 12.51 Hz, JP−H = 6.93 Hz, benzoate
Ar-H, cis-isomer), 9.95 (s, 2H, NH, trans isomer), 10.17 (s, 2H, NH,
cis isomer), 13.18 (br, 4H, CO2H). 31P{1H} NMR (162 MHz,
DMSO-d6): δ 71.5 (s, 2P, cis isomer), 90.3 (s, 2P, trans isomer).
ATR-IR: ν(CO) 1974 cm−1.
G
DOI: 10.1021/acs.organomet.9b00482
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Based MOF for Enantioselective Epoxidation. Catal. Sci. Technol.
2019, 9, 3388−3397.
Notes
The authors declare no competing financial interest.
(15) Alkordi, M. H.; Liu, Y.; Larsen, R. W.; Eubank, J. F.; Eddaoudi,
M. Zeolite-like Metal-Organic Frameworks as Platforms for
Applications: On Metalloporphyrin-Based Catalysts. J. Am. Chem.
Soc. 2008, 130, 12639−12641.
ACKNOWLEDGMENTS
■
Acknowledgment is made to the Donors of the American
Chemical Society Petroleum Research Fund (Grant 55281-
DNI-3) for support of this research. M.B.G. and P.M.W. were
supported by the National Science Foundation under award
number DMR-1610631. Use of the Advanced Photon Source
at Argonne National Laboratory was supported by the U.S.
Department of Energy (DOE) Office of Science under
Contract DE-AC02-06CH11357. Synchrotron diffraction
data were collected using the 11-BM mail-in rapid access
program with GUP-54588.
(16) Juan-Alcaniz, J.; Ramos-Fernandez, E. V.; Lafont, U.; Gascon,
̃
J.; Kapteijn, F. Building MOF Bottles around Phosphotungstic Acid
Ships: One-Pot Synthesis of Bi-Functional Polyoxometalate-MIL-101
Catalysts. J. Catal. 2010, 269, 229−241.
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“MetalloMOFzymes”: Metal-Organic Frameworks with Single-Site
Metal Catalysts for Small-Molecule Transformations. Inorg. Chem.
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Vermeulen, N. A.; Cramer, C. J.; Gagliardi, L.; Hupp, J. T.; Farha, O.
K. An Exceptionally Stable Metal−Organic Framework Supported
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