Organotextile catalysis

Article abstract of DOI:10.1126/science.1242196

Throughout human history, textiles have been integral to daily life, but their exploration in catalysis has been rare. Herein, we show a facile and permanent immobilization of organocatalysts on the textile nylon using ultraviolet light. The catalyst and

Full text of DOI:10.1126/science.1242196

Organotextile Catalysis
Ji-Woong Lee et al.
Science 341, 1225 (2013);
DOI: 10.1126/science.1242196
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of Science, Office of Basic Energy Sciences award DE-SC0000989.
M.R.J. acknowledges a Graduate Research Fellowship from NSF;
E. A. acknowledges the Department of Defense for a National
Defense Science and Engineering Graduate Fellowship. Portions
of this work were carried out at the DuPont-Northwestern-Dow
Collaborative Access Team (DND-CAT) beamline located at Sector
5 of the Advanced Photon Source (APS). DND-CAT is supported by
E. I. DuPont de Nemours & Co., Dow Chemical Company, and the
state of Illinois. Use of the APS was supported by the U.S. DOE,
Office of Science, Office of Basic Energy Sciences, under contract
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Supplementary Materials
www.sciencemag.org/cgi/content/full/science.1241402/DC1
Materials and Methods
Supplementary Text
Figs. S1 to S25
Acknowledgments: We thank M. Kanatzidis for helpful
discussions regarding the ternary crystal structures synthesized
and their corresponding atomic analogs. This material is
based on work supported by Air Force Office of Scientific Research
awards FA9550-11-1-0275, FA9550-12-1-0280, and
FA9550-09-1-0294; Defense Advanced Research Projects Agency
award HR0011-13-2-0002; NSF–Materials Research Science and
Engineering Center (MRSEC) program DMR-0520513; and the
Non-equilibrium Energy Research Center, an Energy Frontier
Research Center funded by Department of Energy (DOE), Office
Tables S1 to S4
References (35, 36)
3 June 2013; accepted 12 August 2013
Published online 22 August 2013;
10.1126/science.1241402
preparation and use of several textile-immobilized
organocatalysts, which display excellent activity,
selectivity, and recyclability.
Textiles have previously been used as solid sup-
ports for nanosized components, such as graphene
and carbon nanotubes via physical absorption
or adhesion (9–12). In 1935, Bredig et al. used
Organotextile Catalysis
Ji-Woong Lee,1 Thomas Mayer-Gall,2 Klaus Opwis,2* Choong Eui Song,3
Jochen Stefan Gutmann,2,4 Benjamin List1*
Throughout human history, textiles have been integral to daily life, but their exploration in
catalysis has been rare. Herein, we show a facile and permanent immobilization of organocatalysts amine-functionalized organic fibers (i.e., cellulose
on the textile nylon using ultraviolet light. The catalyst and the textile material require no chemical and cotton) as catalysts for a cyanohydrin forma-
modification for the immobilization. All of the prepared textile-immobilized organocatalysts
(a Lewis basic, a Brønsted acidic, and a chiral organocatalyst) display excellent stability, activity,
and recyclability for various organic transformations. Very good enantioselectivity (>95:5
tion reaction (13). Recently, a heterobimetallic
complex (Pd/Co) was prepared by using wool as
a ligand and applied in asymmetric hydration of
enantiomeric ratio) can be maintained for more than 250 cycles of asymmetric catalysis. Practical unsaturated carboxylic acids (14). However, as of
and straightforward applications of textile organocatalysis may be beneficial for various fields
by offering inexpensive and accessible functionalized catalytic materials.
yet textile materials have not been used as a gen-
eral solid support for organic compounds in se-
lective catalysis. During our own research, we
atalysis with small organic molecules has venting leaching out of catalytically active centers have found that the irradiation of textiles can
been intensively investigated in recent (4–6). To access heterogeneous organocatalysts, result in the photochemical production of surface
years, providing distinct reactivity, activ- research has focused on immobilizing the cat- radicals, which can be used to further function-
C
ity, and selectivity that complement biocatalysis alysts on diverse solid materials (7). However, a alize the textile with organic molecules and bio-
and transition metal catalysis. Organocatalysts are general and convenient method for the immo- catalysts (15–17). Therefore, we presumed that this
metal-free and display Lewis acidic or basic and bilization of different types of organocatalysts that strategy could be applied in a facile preparation
Brønsted acidic or basic reactivity (1–3). Despite addresses stability, reactivity, and recyclability of of solid-supported organocatalysts under photo-
fruitful advancements in academia, further ap- the obtained hetereogeneous material has not been chemical reaction conditions.
plication of organocatalysts in industry is often established previously.
We commenced our study by investigating the
hampered by their relatively low turnover effi- We recently became interested in identifying immobilization of three representative organo-
ciency, even though exceptions exist. The immo- inexpensive and abundant polymeric solid mate- catalysts, a dimethylaminopyridine (DMAP) de-
bilization of organocatalysts via a covalent bonding rials that would support organocatalysts while rivative, a sulfonic acid, and a bifunctional chiral
interaction could provide a general solution, pre- displaying various practical advantages, such as organocatalyst, using nylon as support (Fig. 1).
high flexibility, durability, versatility, and broad Gratifyingly, all organocatalysts (1a, 2, and 3)
accessibility. Since the early 1930s, by taking ad- were successfully immobilized on the textile and
1Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-
Platz 1, 45470 Mülheim an der Ruhr, Germany. 2Deutsches
Textilforschungszentrum Nord-West gGmbH, Adlerstraße 1,
47798 Krefeld, Germany. 3Department of Chemistry, Sungkyunkwan
University, 300 Cheoncheon, Jangan, Suwon, Gyeonggi, 440-
746, Korea. 4Institute of Physical Chemistry and CENIDE (Center
for Nanointegration), University Duisburg-Essen, Universitätsstraße
5, 45117 Essen, Germany.
vantage of organic chemistry and polymer tech- fully analyzed by various methods (see tables S1
nologies, synthetic textiles have been produced to S5 for immobilization reaction conditions).
on a large scale (8). However, chemical applica- The catalyst loading can be controlled by adding
tions of textile materials have been rare, possibly a cross-linker, such as PETA (penta-erythritol tri-
because of its perceived inertness for further acrylate) (18). Lewis basic catalyst 1a, Brønsted
manipulations. We realized the potential of in- acid catalyst 2, and bifunctional organocatalyst
dustrially produced textile materials as support 3a, which possesses both a basic and an acidic
for organic catalysts and now report here the functionality, were equally tolerated under the
*Corresponding author. E-mail: opwis@dtnw.de (K.O.); list@
kofo.mpg.de (B.L.)
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photochemical reaction conditions yielding tex- with isobutyric anhydride (Fig. 2A) (19). In the ab- In more than 10 recycling experiments, no signif-
tile catalysts OrganoTexCat-1a, -2 and -3a with sence of catalyst OrganoTexCat-1a or in the presence icant erosion of the catalytic activity was observed.
catalyst loadings of up to 0.025 mmol/g. Irradiation of blank polyamide instead of OrganoTexCat-1a, The catalyst can be deactivated by forming an
time proved critical for both catalyst loading and only insignificant background reaction was ob- acid-base salt with the carboxylic acid by-product
catalytic activity (vide infra). A short irradiation served under otherwise identical reaction condi- of the reaction (fourth run in Fig. 2B). However,
time (5 min) for each side of the textile could im- tions. After full conversion of starting material 4, the catalytic activity could be readily recovered
prove the catalyst loading while preventing any the catalyst was easily recovered by decanting the by washing with triethylamine to regenerate the cat-
degradation of the textile and the organic catalysts. liquid phase, simply washing with an organic sol- alyst with good activity.
Next, the catalytic activity and recyclability of vent, and drying by blowing air onto the textile.
In addition to OrganoTexCat-1, we prepared
catalyst OrganoTexCat-1a was investigated in the Several recycling experiments revealed the robust- several other textile-supported DMAP variants with
acylation reaction of sterically demanding phenol 4 ness of our catalyst OrganoTexCat-1a (Fig. 2B). different linker groups (fig. S4). These Lewis ba-
Fig. 1. Reaction conditions for the photochemical immobilization. The from a water/ethanol (1:1) solution. The catalyst loading was determined by
textile was irradiated with ultraviolet light for 5 min on each side of the textile elemental analysis. (D) Immobilization of bifunctional chiral catalyst 3 on tex-
wetted by a solution of the organic catalyst. (A) Immobilization of DMAP derivative tile from an acetonitrile solution. Catalyst loading was determined by elemental
1a on textile from an acetonitrile solution. The catalyst loading was determined by analysis, MAS (magic-angle solid-state) 19F NMR spectroscopy (fig. S1), and XPS
acid/base titration. Me, methyl group. (B) Scanning electron microscope image of analysis (figs. S2 and S3). (E) A photograph of catalyst OrganoTexCat-3a
OrganoTexCat-1a. (C) Immobilization of p-styrenesulfonic acid (2) on textile (numbers indicate the catalyst loading per gram of sheet).
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sic catalysts can also be used in a carbonate-forming of the microenvironment of the catalytically active was obtained with more than 95:5 er without
reaction from epoxide 6 (20). OrganoTexCat- sites (22, 23). erosion of enantioselectivities for more than 220
1d, which showed the highest activity after optimi- Cinchona alkaloids, naturally occurring chiral cycles. After 200 cycles, a slight deactivation of
zation of the side chain structure, demonstrated molecules with various functional groups, have OrganoTexCat-3a was observed and resulted in a
reasonable activity for this reaction in supercrit- emerged as privileged ligands and organocat- lower enantioselectivity (94:6 er). However, in-
ical CO2 (Fig. 2C). OrganoTexCat-1d could be alysts for various catalytic asymmetric transfor- creasing the catalyst loading to 10 mol % led to
easily recycled and showed identical activity for mations (24). With cinchona-sulfonamide–based an increase of the enantioselectivity back to 95:5
seven cycles affording cyclic carbonate 7 without OrganoTexCat-3a in our hands, we evaluated er (231st cycle). Therefore, we concluded that the
considerable formation of polymeric by-products. activity and recyclability by performing the alco- chemical structure of the chiral catalyst was indeed
This result highlights the high stability of the holytic desymmetrization of cyclic anhydride 10 intact. The loss of activity and enantioselectivity
catalyst under high pressure (100 atm) and tem- (25–27). OrganoTexCat-3a showed a very similar could be ascribed to the detachment of a certain
peratures (up to 75°C), which might be beneficial enantioselectivity [96.5:3.5 enantiomeric ratio (er)] amount of the catalytically active species from the
for further applications.
Highly Brønsted acidic heterogeneous cata- quiring a somewhat longer reaction time (Fig. 3A). in the presence of excess of methanol.
lysts are of great interest in industrial chemical After the photochemical preparation of cata- The substrate scope of OrganoTexCat-3a for
to homogeneous catalyst 3a (97:3 er) although re- textile after more than 300 recycling experiments
production (21). As shown in Fig. 2D, acidic lyst OrganoTexCat-3a, residual homogenous the desymmetrization of different meso-anhydrides
OrganoTexCat-2 displays good activity in an catalyst 3a could be recovered and reused for has also been determined and is summarized in
intramolecular hydroetherification, affording the subsequent immobilization reactions (figs. S5 and Fig. 4A. Various meso-anhydrides were smooth-
corresponding tetrahydrofuran in excellent yield. S6). Furthermore, the robustness of OrganoTexCat- ly transformed into enantioenriched hemiesters
No background reaction was observed in the ab- 3a is illustrated with hundreds of recycling ex- with excellent yields (up to 99%) and enantio-
sence of the catalyst. The immobilized acidic cat- periments (Fig. 3B). By varying the reaction selectivities (er up to 97:3). Bi- and tricyclic com-
alyst is easy to handle and features robust stability conditions, such as the amount of nucleophile pounds could also be used to afford the desired
for the transformation, which are the primary ad- and the concentration of the substrate, we ob- products with high enantioselectivities and com-
vantages of polymer-supported catalysts.
tained an optimal enantioselectivity (er up to 97:3). parable selectivity to the homogeneous catalysis
After establishing a facile immobilization meth- This result is comparable to the homogeneous conditions. Moreover, product 11h, a valuable pre-
odology for organocatalysts on textile materials reaction conditions with 5 to 10 mole percent cursor of statin derivatives (27), could be obtained
and applying them successfully to three different (mol %) of catalyst loading of 3a. Moreover, the on a gram scale by using a flow reactor with an
classes of transformations, we turned our atten- catalyst loading could be decreased to 4 mol % OrganoTexCat-3a packed column in an iterative
tion to asymmetric catalysis. Although various at- without loss of enantioselectivity (77th to 81st continuous reaction (Fig. 4B). The column was
tempts have been made to provide heterogeneous cycles). To investigate the fate of our catalyst, we prepared without any sophisticated packing pro-
chiral organocatalysts, they typically give inferior conducted further recycling experiments by using cedure, contrary to powder- or resin-based hetero-
stereoselectivity, possibly because of the alteration 6 mol % of the catalyst, and the desired product geneous catalysts. The textile material showed
Fig. 2. Reactions using textile-supported achiral catalysts. (A) Acylation reaction of phenol 4 to ester 5. Et,
ethyl group; Ph, phenyl group; i-Pr, isopropyl; eq, equivalent. (B) Recycling experiments of OrganoTexCat-1a
(reaction conditions: 8 mol % of catalyst loading, 36 hours in CH2Cl2, [4] = 0.05 M). The numbers in the parentheses are isolated yields of the acylated
product. *After the fourth cycle, each experiment was conducted with the triethylamine-washed textile catalyst. (C) A carbonate-forming reaction catalyzed by
OrganoTexCat-1d. scCO2 indicates supercritical CO2 reaction conditions. (D) A hydroetherification reaction using acidic OrganoTexCat-2.
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good absorption ability for organic solvents, which washed with methyl tert-butyl ether (MTBE) This leads to a uniform three-dimensional coat-
can facilitate mass transfer onto the material, gen- and reused 10 times, showing identical activity ing. Moreover, the active surface area is easily
erating a microfluidic environment via capillary and enantioselectivity. adjustable by varying the fiber diameter, which
action to increase the effective catalyst concen- In addition to the robustness of our organo- should ultimately enable preparation of organo-
tration. As shown in Fig. 4C, enantioenriched textile catalysts, several aspects should be high- textiles with significantly higher catalyst loadings.
product 11h was obtained in quantitative yield lighted. Compared with polymer films, textile The flexible construction of fabrics allows reactor
(>99% yield) and excellent enantioselectivity fibers exhibit a much higher surface area. The constructions of arbitrary geometry and a quick
(up to 97:3 er) by taking advantage of a simple inherent capillary action of textiles allows an easy removal of the catalyst. Our results underscore
fixed-bed reactor setup (28, 29). After full con- and uniform wetting of the material with the cat- the vast potential of supported organocatalysts for
version of the starting material, the column was alyst before the photoinduced immobilization. chemical synthesis (30).
Fig. 3. Performance of the textile-supported chiral catalyst. (A) Comparison of the activity of homogeneous catalyst 3a and heterogeneous
OrganoTexCat-3a. r.t., room temperature. (B) Recycling experiments. For experimental details, see table S6.
Fig. 4. Substrate scope and applications of OrganoTexCat-3a. (A) Sub- illustration of the continuous circle reactor and the picture of the reaction
strate scope of the desymmetrization of anhydrides 10 catalyzed by setup. P, pump; C, column packed with OrganoTexCat-3a. (C) Desymme-
textile OrganoTexCat-3a. *15 mol % of catalyst OrganoTexCat-3a was trization of silylated glutamic anhydride; see table S7 and fig. S7 for the
used. †50 mol % of catalyst OrganoTexCat-3a was used. (B) Schematic optimization of reaction conditions. t-Bu, tertbutyl.
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DECHEMA (Gesellschaft für Chemische Technik und
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Supplementary Materials
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Materials and Methods
Supplementary Text
Figs. S1 to S8
Tables S1 to S8
Supplementary Data
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earthquakes (Fig. 1). We sheared layers of lizardite-
rich serpentinite at constant normal stress of 1 MPa
(supplementary text). Each experiment includes
50+ stick-slip events, with durations ranging up
to 35 s (Fig. 2). Our experiments show that the
laboratory fault zones undergo a transition from
velocity-weakening to velocity-strengthening fric-
tion behavior above slip rates of ~10 mm/s (Fig. 3).
During each slip event, the fault zone shows large
changes in elastic wave speed (2 to 21% de-
crease), with precursory changes of 1 to 3% start-
ing up to 60 s before failure (Fig. 4).
Like natural earthquakes, fault slip velocity
during stick-slip events exceeded the imposed
far-field velocity. The full record for one experi-
ment shows the character of stress drops and
the corresponding stair-step pattern of fault dis-
placement (Fig. 1A). Stick-slip events have dura-
tions of 1 to 35 s, average slip velocities of 15 to
280 mm/s, average displacements of 10 to 900 mm,
and evolve from small to large events with in-
creasing shear (Fig. 1B). We observed slow stick-
slip events at a range of loading velocities (Fig.
2). Each event generally released tens of kilopascals
of shear stress—roughly a 5 to 10% stress drop
(Fig. 1A). Maximum slip velocities ranged from
60 to 1300 mm/s, but peak velocities were gen-
erally sustained for <1 s, with longer acceleration
and deceleration periods (Fig. 2B). The events re-
semble results from experiments conducted on
halite (12) but are distinguished by their consist-
ent, repetitive nature.
Slow Earthquakes, Preseismic
Velocity Changes, and the Origin
of Slow Frictional Stick-Slip
Bryan M. Kaproth and C. Marone
Earthquakes normally occur as frictional stick-slip instabilities, resulting in catastrophic failure
and seismic rupture. Tectonic faults also fail in slow earthquakes with rupture durations of months
or more, yet their origin is poorly understood. Here, we present laboratory observations of
repetitive, slow stick-slip in serpentinite fault zones and mechanical evidence for their origin.
We document a transition from unstable to stable frictional behavior with increasing slip velocity,
providing a mechanism to limit the speed of slow earthquakes. We also document reduction of
P-wave speed within the active shear zone before stick-slip events. If similar mechanisms operate
in nature, our results suggest that higher-resolution studies of elastic properties in tectonic fault
zones may aid in the search for reliable earthquake precursors.
low earthquakes represent one mode of the identifying possible precursory changes in fault
spectrum of fault slip behaviors ranging zone properties are increasingly important goals.
S
from steady aseismic slip at plate tectonic
Although observations of slow earthquakes
rates (a few millimeters per year) to normal earth- abound, the underlying processes that produce
quakes with rupture propagation at a few kilome- these self-sustaining, quasi-dynamic ruptures re-
ters per second and fault slip speeds of 1 to 10 m/s, main poorly understood (3–8). A particularly vex-
which is consistent with elastodynamic theory ing aspect of slow earthquakes is the mechanism
(1–6). Like normal earthquakes, slow earthquakes that limits slip speed yet allows self-sustained
can accommodate most of a fault’s slip budget, rupture propagation. One possibility is that slow
with equivalent magnitudes of 8 or larger; yet, this earthquakes represent prematurely arrested nor-
slip occurs slowly, over days to years, rather than mal earthquakes with slip-speed limited by a
the few tens of seconds for normal earthquakes mechanism such as dilatant hardening or a tran-
(1–4). Slow earthquakes often occur adjacent to sition in friction constitutive behavior with in-
traditional seismogenic zones (5, 7) and may load creasing slip speed. Several mechanisms have
these earthquake-prone areas. Moreover, recent been proposed (4–12), but the origin of slow
work suggests that slow earthquakes may abet earthquakes remains elusive. Additionally, if slow
potentially devastating earthquakes, such as the earthquakes initiate like normal earthquakes they
2011 Mw 9 Tohoku Oki earthquake (7), and thus, may exhibit precursory effects, such as acceler-
understanding the physics of slow earthquakes and ating fault slip or changes in elastic wave-speed
within the rupture nucleation region.
To investigate the processes responsible for
these slow-slip events, we conducted additional
experiments under stiff loading conditions, includ-
ing slide-hold-slide (SHS) (fig. S2) and velocity-
step tests (fig. S3). We determined the friction
rate parameter (a-b = ∆m/∆lnV, where V is the
velocity) and critical slip distance (Dc) using
standard techniques (13). With increased shear
strain and hold time, (a-b) generally decreased,
and Dc increased (fig. S2A). At slip velocities
Here, we describe laboratory observations of
fault-zone materials showing repetitive, slow stick-
slip friction events that are reminiscent of slow
Department of Geosciences, and Energy Institute Center for
Geomechanics, Geofluids and Geohazards, Pennsylvania State
University, University Park, PA 16802, USA.
www.sciencemag.org SCIENCE VOL 341 13 SEPTEMBER 2013
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