Atomic Layer Deposition of RheniumâAluminum Oxide Thin Films and

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Atomic Layer Deposition of Rhenium-Aluminum Oxide Thin Films and ReO Incorporation in a Metal–Organic Framework x

Martino Rimoldi, Joseph T. Hupp, and Omar K. Farha ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b12303 • Publication Date (Web): 20 Sep 2017 Downloaded from http://pubs.acs.org on September 21, 2017

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ACS Applied Materials & Interfaces

Atomic Layer Deposition of Rh Rheniumnium-Aluminum Aluminum Oxide Thin Films Films and ReOx Incorporation in a Metal– Metal–Organic Framework Martino Rimoldi, a Joseph T. Hupp, a and Omar K. Farha a, b,* a

Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States. Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia. KEYWORDS. Atomic Layer Deposition, Rhenium Oxide, Trimethylaluminum, Thin Film, Metal–Organic Framework, Hydrogenation, Gas Flow. b

ABSTRACT: Methyltrioxorhenium (ReO3Me) is introduced as the first rhenium atomic layer deposition (ALD) precursor and used to grow rhenium aluminum oxide thin films in combination with trimethylaluminum (TMA – AlMe3). The growth rate of the smooth Re-Al oxide films, with general stoichiometry RexAlyO3x, has been monitored by in situ quartz crystal microbalance (QCM) and ex situ ellipsometry, and found to be 3.2 Å/cycle. X-ray photoelectron spectroscopy (XPS) revealed the mixed valent composition of the film with Re(III) species being the main component. In addition, ReO3Me has been successfully used to deposit rhenium oxide in NU-1000, a mesoporous zirconium-based metal–organic framework (MOF). The metallated MOF was found to retain porosity, crystallinity and to be catalytically active for ethene hydrogenation.

INTRODUCTION Atomic layer deposition (ALD)1, 2 – an atomic scale vaporphase deposition technique based on self-limiting interfacial chemical reactions – has been widely used in several aspects of electronic device fabrication.3-6 ALD procedures are in constant development in order to access more scalable and easily engineered deposition processes. For instance, great efforts are currently directed toward achieving deposition under mild conditions,7-10 and a key aspect of this resides in the identification of optimal precursors for each element requiring deposition.11-14 Typical precursors consist of molecular organometallic species bearing ligands that can be easily hydrolyzed and removed by vacuum in their neutral form, such as alkyls, halides, β-diketonates, cyclopentadienyls, alkoxides, and amides. Given the vapor-phase nature of the process, in order to be effectively delivered to the deposition chamber, an ALD precursor needs to be both chemically stable and sufficiently volatile at the required operating temperature. To date, the vast majority of elements has been utilized or proven applicable to atomic layer deposition. However, to our knowledge, rhenium is the only naturally occurring d-block element that has not been reported in an ALD process.5, 11, 1315 Over time however, various methods have been developed to achieve deposition of mixed-valent rhenium oxide thin films. The methods include electrochemical deposition,16 evaporation from a heated rhenium wire,17 and magnetron sputtering.18-20 Because of their optical and chemical properties, as well as their conductivity, rhenium oxide films are potentially useful as component materials in a number of technologies.18, 20-24 More recently, ALD found applications in mesoporous materials functionalization 25-30 and has also emerged as a unique

tool in catalysts synthesis and design.31, 32 Generally, rheniumbased heterogeneous catalysts have been broadly investigated, and the known systems largely consist of rhenium oxide species, metallic rhenium nanoparticles, and also single atom species deposited on a variety of oxide supports, that include, for instance, carbons,33, 34 silicas,35 aluminas,36, 37 and zeolites.33, 34 Especially due totheir catalytic relevance, oxo-rhenium species confined within zeolite frameworks 38, 39 have been investigated and particular emphasis was placed on size control over the units incorporated within the zeolites cages and on the understanding of their molecular nature.In particular, rhenium oxide nanoparticles or rhenium oxide clusters deposited over high surface area supports attracted importance because of their relevance in industrial applications.40 Principally known for their activity in alkene metathesis,36, 42-44 rhenium oxide-based catalysts also demonstrated their potential in other catalytic transformations of practical relevance, such as alcohols dehydration,35, 37 methanol oxidation,41, 42 and hydrogenation reactions.33, 34 Given the lack of ALD processes involving rhenium, herein we investigate the self-limiting, vapor-phase deposition of rhenium oxide assisted by trimethylaluminum (TMA) to yield rhenium aluminum oxide thin films. In addition, the rhenium complex here used for thin films deposition has also been successfully applied to the deposition of ReOx catalytic functions into a mesoporous material. In particular, we adopted a vapor phase process closely related to ALD to install oxo-rhenium units onto the zirconium-oxide node of the mesoporous and highly stable metal–organic framework NU-1000. The obtained Re-NU-1000 material is found to contain rhenium oxide species able to catalyize alkene hydrogenation in gas flow conditions.

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RESULTS AND DISCUSSION Rhenium oxides are the most common and easily accessible rhenium compounds. They can occur in various oxidation states including Re(VII), Re(VI), and Re(IV), as exemplified by Re2O7, ReO3, and ReO2, respectively. However, the very high melting point of these species limits their ability to generate significant vapor pressure, a property that is crucial for a vapor-phase deposition technique. Methyltrioxorhenium (ReO3Me), a well-known Re(VII) synthetic derivative of Re2O7, is an exception.43 It is highly volatile and also contains an alkyl ligand – a feature that makes it an interesting precursor in terms of reactivity. Thermogravimetric analysis (TGA) at atmospheric pressure demonstrates that ReO3Me evaporates at modest temperatures with no signs of decomposition (Figure 1). In particular, the TGA shows that mass loss initiates approximately at 50 °C with complete evaporation/sublimation occurring below 100 °C. The TGA curve additionally implies that ReO3Me is thermally stable, since there are no signs of residual solid. Such behavior makes this complex an excellent candidate for vaporphase applications, and in particular ALD.

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quence of AB binary cycles, alternating sequential doses of ReO3Me (A cycle) and TMA (B cycle). In general, the Re-Al oxide films were deposited following a t1-t2-t3-t4 timing sequence, where t1 is the time during which the rhenium precursor is exposed to the deposition chamber (ReO3Me pulse time), t2 is the purge time following one ReO3Me dose necessary to remove unreacted precursor and possible secondary products (ReO3Me purge time), t3 is the TMA pulse time, and t4 is the TMA purge time, and adopting the temperature setting T1-T2-T3, where T1 is the temperature at which ReO3Me is heated to generate its vapors (ReO3Me temperature), T2 is the TMA temperature, and T3 is the deposition chamber temperature. Figure 2b shows a representative QCM record of a few AB cycles of ReO3Me and TMA which provides insight into the deposition process. The red trace (gray background in Figure 2b) shows the dosing of ReO3Me (A cycle) into the ALD chamber and the subsequent purging via N2 flow at reduced pressure. The apparent spikes in film mass observed at the start of each ReO3Me dose are most likely artifactual, and reflect transient changes of the oscillation of the quartz crystals as a result of pressure variations in the chamber upon dosing the precursor. Alternatively, they might possibly be indicative of transient physisorption and release of ReO3Me (in addition to irreversible chemisorption) onto the growing film. In any case, the spikes are too large to be explained, for example, by slow release of ethane following deposition of ReO3Me onto an Al(III)-rich surface. The QCM trace related to the B cycle (TMA doses) is depicted in blue. The ∆m1 and ∆m2 in Figure 2b refers to the mass gain (ng cm-2) obtained after a ReO3Me and TMA dose, respectively.

Figure 1. Thermogravimetric analysis (TGA) of ReO3Me.

ALD studies were conducted on a wall-mounted custommade reactor lid equipped with commercial quartz crystal microbalance (QCM) sensors, allowing for in situ growth monitoring.44 First, we interrogated the suitability of ReO3Me as an ALD precursor by evaluating its self-limiting behavior. Upon repeatedly dosing vapors of ReO3Me, the mass gain measured by QCM was found to plateau after a few precursor doses, indicative of self-limiting behavior – a feature distinctive of an ALD process (Figure S1). Since attempts directed at growing rhenium oxide films using ReO3Me and an oxygen source such as H2O, O2, or H2O2 proved unsuccessful, we turned to an ALD process that makes use of TMA as a co-reactant. Oxide film deposition based on bimetallic or multi-element ALD processes have recently been developed for various film compositions, including a number of examples that make use of TMA as a co-reactant.45-50 Figure 2a shows a typical QCM trace using a bimetallic approach. QCM crystals were first coated with a few nanometers of amorphous Al2O3 prepared by ALD (alternating doses of TMA and H2O) in order to establish a smooth and uniform oxide layer presenting a reproducible concentration of surface hydroxyls. Then the Re-Al oxide film was deposited via a se-


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ACS Applied Materials & Interfaces Figure 2. a) Representative QCM trace: Re-Al oxide film grown with 25 ReO3Me-TMA cycles (blue background). b) QCM details of three ReO3Me – TMA cycles. Red trace (A cycle): ReO3Me pulse time + purge time; blue trace (B cycle): TMA pulse time + purge time; black trace: pre-run. ∆m1 = mass gain due to a ReO3Me dose; ∆m2 = mass gain due to an TMA dose.



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Figure 3. Mass gain per cycle (ng cm-2) as determined by a quartz crystal microbalance (QCM) varying the (a) ReO3Me pulse time, (b) TMA pulse time, (c) ReO3Me purge time, and (d) deposition temperature. General conditions adopted in the QCM studies: ReO3Me pulse time: 2s, ReO3Me purge time: 30s, TMA pulse time: 0.015s, TMA purge time: 30 s; ReO3Me temperature: 70 °C, TMA temperature: 25 °C, deposition temperature: 120 °C.

Next, we investigated the effect of ALD dosing parameters on film deposition, again using QCM (Figure 3).51 The ReO3Me pulse time was varied from 0.1 to 4 s. Initially, longer pulses (corresponding to delivery of more vapor to the reaction chamber) translate to higher growth rate (Figure 3a). The mass increase plateaus, however, at a ReO3Me pulse time ca. 2 s, with a mass gain per cycle of 104.5 (± 0.2) nm cm-2. The efficacy of TMA delivery and deposition was also similarly tested by varying the TMA pulse time from of 0.015 to 0.2 s (Figure 3b). Given the high volatility of this liquid precursor and its high reactivity, no variations in the growth rate were observed, indicating use of the (shorter) 0.015 s pulse as the optimal dosage time. Additionally, we investigated the effect of ReO3Me purge time, a critical step that allows the removal of unreacted and physisorbed precursor, in addition to secondary products (if any). As shown in Figure 3c, negligible differences in film growth were observed upon increasing the purge time from 30 to 60 s, establishing that a 30 s purge time is sufficient to remove unreacted ReO3Me from film and chamber. Within the explored range (100 to 170 oC; see Figure 3d), the deposition temperature was observed to have only a minor influence on the mass gain. The QCM data in Figure 2a shows that the Re-Al oxide film growth is uniform and linear with respect to the number of AB

cycles. The linearity of ex situ ellipsometry data (on alumina coated silicon wafers; see Figure 4) supports a linear film growth, corroborating the QCM findings.52 For these experiments, the wafers were subjected to a variable number of AB cycles in order to grow films spanning a range of thicknesses. The timing sequence was t1-t2-t3-t4 = 2-30-0.015-30 s and the temperature settings were T1, T2, and T3 = 70, 25, and 120 °C. Returning to Figure 4, the ellipsometry measurements additionally reveal that the growth rate, averaged over the course of 100 AB cycles, is ca. 3.2 Å per cycle. The reported growth rate value of 3.2 Ǻ/cycle refers to the combined AB cycles and is relatively high when compared to the deposition of metal oxides. However, this value is in line with other binary ALD processes – specifically when coupling a metal precursor with TMA – such as PrxAl2-xO3 45 or TaAlC.50


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Figure 4. Film thickness (nm) vs number of AB ALD cycles as measured by ellipsometry. Error bars represent standard deviation values.

Consistent with uniform growth, the films were found to be smooth, as demonstrated by atomic force microscopy (AFM). Figure 5 shows a representative 1 µm × 1 µm AFM image of a 16 nm thick film (obtained from 50 ALD cycles) that shows a root mean square (rms) roughness (Rq) of 0.22 nm, indicative of a nearly atomically smooth film. This value is close to the roughness of the alumina under-layer deposited on the silicon wafer (0.15 nm, Figure S7) and only slightly increases with increasing thickness (Rq is 0.24 nm for a 24 nm thick film, Figure S8).

The film structure was also investigated by XPS. The Re 4f XP spectrum of the top layer of the Re-Al oxide film is shown in Figure 6a.55 The spectrum can be deconvoluted into three components, with Re 4f7/2 binding energies (BEs) of 46.4, 43.3, and 42.2 eV. Re 4f7/2 BEs for the Re(VII) and Re(VI) reference materials Re2O7 and ReO3 were found to be 46.4 eV and 45.0 eV, respectively, in close agreement with literature values of 46.4 eV 20, 56 and 45.2 eV 56, respectively. Also, literature Re 4f7/2 BEs for Re(IV) and Re(III) species are reported to be 43.4 eV 56 or 42.9 eV 20, and 42.1 eV 56 or 42.4 eV 20, respectively. Based on the reference values, we can assign the peaks found at 46.4, 43.4, and 42.2 eV to Re(VII), Re(IV), and Re(III) 4f7/2 BE, respectively (Figure 6a). In order to probe the electronic structure of the film below its surface, a film was subjected to Ar ion beam etching (approximately 2.5 nm). The acquired XP spectrum (Figure 6b) could be deconvoluted into three components with Re 4f7/2 BEs of 45.3 eV, 43.4 eV, and 42.2 eV., i.e. peaks characteristic of Re(VI), Re(IV), and Re(III). Notably absent is a component attributable to Re(VII).57 The spectroscopic differences between the top layer and the bulk of the film are attributed to surface oxidation upon exposure of the film to air. The area ratios of the Re 4f7/2 peaks (1:0.27:0.05) point to Re(III) as the predominant oxidation state, with Re(IV) constituting only a minor constituent and Re(VI) constituting an even smaller amounts (Figure 6b). Depth profiling revealed no further change in oxidation-state distribution.58

Figure 5. 1 µm × 1 µm atomic force microscope (AFM) image of a 16 nm thick film. Roughness (Rq): 0.22 nm.

Since the ALD process does not involve any oxygen source other than the rhenium oxide precursor itself, its structure can be described with the generic RexAlyO3x stoichiometry. Moreover, inductively coupled plasma-optical emission spectroscopy (ICP-OES) measurements were used to determine a Re : Al ratio of 1 : 1.8,53 whereas an Al : O ratio of 1.8 : 2.9 was determined by X-ray photoelectron spectroscopy (XPS),54 supporting a Re : O ratio consistent with the RexAlyO3x stoichiometry.



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Figure 6. a) Re 4f x-ray photoelectron spectrum of the Re-Al oxide film top layer and b) after ion beam etching.

Given that the ALD precursor contains rhenium exclusively in oxidation state VII, rhenium reduction evidently accompanies Re-Al oxide film formation. We speculate that the Al– CH3 moiety of TMA reacts with Re=O to generate a Re–O–Al bond concomitantly transferring a methyl group to the rhenium center, analogous to the postulated reactivity of Al2O3supported rhenium oxide catalysts with tetramethyltin (SnMe4).59 Once the rhenium center bears two methyl ligands, a reductive elimination step can promote the release of ethane (CH3–CH3), ultimately lowering the rhenium oxidation number. However, given the occurrence of multiple oxidation states, more complex scenarios involving, for instance, the formation of Re–Re and Re–Al bonds are also probable. To illustrate an additional vapor-phase application based on the reported rhenium ALD precursor, we post-synthetically incorporated ReOx in the mesoporous zirconium(IV)-clustercontaining metal–organic framework NU-1000.60 Zr-based MOFs have recently been shown to be capable of functioning as high-area platform materials for catalytic applications, i.e. as periodic arrays of nanoscopic, zirconia-like catalyst supports.29, 30, 61-64 Key features are their ability to present open sites for attachment of atomic or molecular catalysts to nodes, their superior chemical and thermal stability, and their ease of tunability.65-67 Recent investigations revealed that NU-1000 is a well-suited platform,27, 60 and that the deposited metal oxide species are confined to the small pores between the Zr6-oxide nodes (Scheme 1).28-30 In a typical procedure, microcrystalline powder NU-1000 is repeatedly dosed in quasi-static mode with ReO3Me vapor in order to fully diffusively permeate the material’s mesopores.

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The XPS spectrum of Re-NU-1000 revealed Re 4f7/2 peaks at 43.8 and 46.3 eV, consistent with Re(VII) and Re(IV) species, respectively (Figure 7). Re(VII) is the predominant component (approximately 80 %) and is thought to be the product of the reactivity between ReO3Me and Zr–OH groups, whereas rationalizing a formation mechanism for the Re(IV) species at this stage is not straightforward. The catalytic activity of the ReOx-functionalized NU-1000 was demonstrated in gas-phase ethene hydrogenation. Catalytic runs were conducted in a stainless-steel vertical tubular reactor equipped with mass flow controllers. Before catalysis, the rhenium oxide functionalized MOF is treated at 190 °C under hydrogen flow (5% H2 in Ar) for 4 hours. Hydrogenation reactions have been conducted at 1 bar (rel.) total pressure, at 190 °C, and at an ethene and hydrogen concentrations of 1.2 % and 3.0 %, respectively. A turn-over frequency (TOF) of 0.14 s-1 has been obtained under differential conditions, at conversion below 10 %, as shown in Figure 8a. TOF value is based on the total rhenium content, i.e. with no attempt to distinguish specific activities of Re(VII) and Re(IV) components. Stability tests were also conducted by monitoring the catalyst activity at a high alkene conversion (approximately 40 %) over a period of time of at least 24 hours.68 As documented in Figure 8b, the prolonged catalytic run (24 h) showed a constant activity, as losses in the conversion level were not observed. The stability over time of the catalytic performance rules out catalyst decomposition or deactivation, demonstrating the robustness of ReOx-NU-1000 and the stability of the active species that take place in the gas phase alkene hydrogenation.

Figure 7. Re 4f x-ray photoelectron spectrum of as-synthesized Re-NU-1000.

Scheme 1. (a) View of NU-1000 perpendicular to the c-axis; (b) View of NU-1000 parallel to the c-axis showing the small apertures in the framework where the oxide clusters are typically located after metalation; (c) Expanded view of linker and zirconium oxide node with its most stable calculated proton topology.

Comparison of powder X-ray diffraction (PXRD) patterns and nitrogen isotherms of the ReOx functionalized Zr-MOF (ReNU-1000) with the parent material confirmed the retention of crystallinity and porosity (Figure S10 and S11).


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ACS Applied Materials & Interfaces proven and benchmarked in alkene hydrogenation, and more importantly, the active species maintained their activity under catalytic conditions for at least one day. Therefore, the newly described rhenium atomic layer deposition process has been successfully used to metallate a mesoporous MOF support with a catalytically active rhenium oxide, a metal oxide that is currently considered of industrial importance.

EXPERIMENTAL SECTION

Figure 8. a) Conversion vs W/F (residence time: (mol Re)/(mol ethene/s)) plot. TOF: 0.14 s-1. Reaction conditions: 190 °C; 1 bar (rel.); ethene concentration: 1.2 %; hydrogen concentration: 3.0 % (H2:C2H4 = 2.5). b) Stability test.

CONCLUSIONS CONCLUSIONS By using the highly volatile ReO3Me complex as a precursor, we find that atomic-layer deposition of rheniumcontaining films can be achieved. To our knowledge, no other peer-reviewed reports of Re-ALD have appeared. In combination with TMA, Re-Al oxide thin films can easily be grown under mild conditions. Atomic force microscopy and in situ quartz crystal microbalance show that the films are smooth and grow homogeneously, whereas Re 4f X-ray photoelectron spectroscopy reveals a mixed valence composition, with a preponderance of the rhenium in oxidation state III. Besides its utility for thin film preparation, we found that ReO3Me could be implemented as a precursor for ALD-like installation of ReOx units on the nodes of the mesorporous MOF, NU-1000, demonstrating the potential general use of the new rhenium ALD precursor to deposit rhenium-oxides over mesoporous supports. The oxo-rhenium units incorporated into the framework comprise rhenium oxides in either oxidation state VII (major) or IV, as result of ReO3Me vapor phase deposition. Additionally, the installed ReOx sites were proved to be suitable for a rhenium-based catalytic transformation. Specifically, the activity of the new ALD-based catalyst has been

Atomic Layer Deposition. ALD of Re-Al oxide films and in situ QCM studies were conducted on a Savannah 200 ALD instrument (Cambridge Nanotech) under a constant 15 sccm flow of dinitrogen. ALD runs followed a t1-t2-t3-t4 timing sequence, where t1 is the ReO3CH3 pulse time, t2 is the ReO3CH3 purge time, t3 is the TMA pulse time, and t4 is the TMA purge time, and adopting the temperature setting T1-T2-T3, where T1 is the temperature at which ReO3Me is heated to generate its vapors (ReO3Me temperature), T2 is the TMA temperature, and T3 is the deposition chamber temperature. T1 and T2 were kept fixed at 70 °C and 23 °C, respectively. Quartz crystal microbalance (QCM) measurements were conducted on a wallmounted custom-made reactor lid equipped with commercially available QCM monitors (Inficon, SQM-160).4 Prior to film deposition, the QCM crystals were coated with alumina by ALD, alternating TMA and H2O doses. Synthesis of Re-NU-1000. In a typical procedure, Re-NU1000 was synthesized in a Savannah 100 ALD reactor. A custom made powder sample holder containing NU-1000 (45 mg) was placed in the ALD reactor heated to 120 °C and subsequently dosed with vapors obtained by heating the rhenium precursor, ReO3Me, to 65 °C and using the following conditions: precursor pulse time: 0.5 s, precursor exposure time: 180 s; purge time: 180 s. Re-NU-1000 samples used in the catalytic test contained 2.1 Re/Zr6 according to the ICP-OES measurements. Catalytic Gas Flow Reactions. Catalytic runs were conducted in a stainless-steel vertical tubular reactor equipped with mass flow controllers. In a typical procedure, Re-NU1000 (40 mg, 2.1 Re /Zr6 node) was diluted with approximately 3 g of SiO2 and deposited in the reactor on a layer of quartz wool. The temperature was controlled by means of a thermocouple placed on the top of the catalyst bed. Before catalysis, the catalyst was exposed to hydrogen flow (5% / Ar) at 190 °C for 4 hours. The reaction was conducted at the total pressure of 1 bar (rel.), 190 °C, and at ethene and hydrogen final concentrations of 1.2 % and 3 %, respectively. The TOF values were obtained under differential conditions, at conversion below 10 %, whereas the stability test was performed at a conversion of approximately 40 % over a period of 24 h. Products were analyzed and quantified by online chromatography using an Agilent 7890A GC equipped with a FID detector and a GSAlumina column (30m x 0.535mm). TOF values are based on the total rhenium content as determined by ICP-OES and reported in s-1.

ASSOCIATED CONTENT Supporting Information. Methods, procedures, and additional experimental data. This material is available free of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION



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Corresponding Author * E-mail: [email protected]

Author Contributions All authors have given approval to the final version of the manuscript.

ACKNOWLEDGMENT This work was supported as part of the Inorganometallic Catalysis Design Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award #DE-SC0012702. This work made use of the EPIC, Keck-II, and SPID facilities of Northwestern University’s NUANCE Center, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205); the MRSEC program (NSF DMR-1121262) at the Materials Research Center; the International Institute for Nanotechnology (IIN); the Keck Foundation; and the State of Illinois, through the IIN. Metal analyses were performed at the Northwestern University Quantitative Bio-element Imaging Center (QBIC).

REFERENCES (1) George, S. M. Atomic Layer Deposition: An Overview. Chem. Rev. 2010, 110, 111–131. (2) Van Bui, H.; Grillo, F.; van Ommen, J. R. Atomic and Molecular Layer Deposition: Off the Beaten Track. Chem. Commun. 2017, 53, 45–71. (3) Leskelä, M.; Ritala, M. Atomic Layer Deposition Chemistry: Recent Developments and Future Challenges. Angew. Chem., Int. Ed. 2003, 42, 5548–5554. (4) Delft, J. A. v.; Garcia-Alonso, D.; Kessels, W. M. M. Atomic Layer Deposition for Photovoltaics: Applications and Prospects for Solar Cell Manufacturing. Semicond. Sci. Technol. 2012, 27, 074002. (5) Johnson, R. W.; Hultqvist, A.; Bent, S. F. A Brief Review of Atomic Layer Deposition: From Fundamentals to Applications. Mater. Today 2014, 17, 236–246. (6) Dasgupta, N. P.; Lee, H.-B.-R.; Bent, S. F.; Weiss, P. S. Recent Advances in Atomic Layer Deposition. Chem. Mater. 2016, 28, 1943–1947. (7) Groner, M. D.; Fabreguette, F. H.; Elam, J. W.; George, S. M. Low-Temperature Al2O3 Atomic Layer Deposition. Chem. Mater. 2004, 16, 639–645. (8) Heo, J.; Hock, A. S.; Gordon, R. G. Low Temperature Atomic Layer Deposition of Tin Oxide. Chem. Mater. 2010, 22, 4964–4973. (9) Mackus, A. J. M.; Garcia-Alonso, D.; Knoops, H. C. M.; Bol, A. A.; Kessels, W. M. M. Room-Temperature Atomic Layer Deposition of Platinum. Chem. Mater. 2013, 25, 1769–1774. (10) Avila, J. R.; Kim, D. W.; Rimoldi, M.; Farha, O. K.; Hupp, J. T. Fabrication of Thin Films of α-Fe2O3 via Atomic Layer Deposition Using Iron Bisamidinate and Water under Mild Growth Conditions. ACS Appl. Mater. Interfaces 2015, 7, 16138–16142. (11) Bernal Ramos, K.; Saly, M. J.; Chabal, Y. J. Precursor Design and Reaction Mechanisms for the Atomic Layer Deposition of Metal Films. Coord. Chem. Rev. 2013, 257, 3271–3281. (12) Knisley, T. J.; Kalutarage, L. C.; Winter, C. H. Precursors and Chemistry for the Atomic Layer Deposition of Metallic First Row Transition Metal Films. Coord. Chem. Rev. 2013, 257, 3222–3231. (13) Hämäläinen, J.; Ritala, M.; Leskelä, M. Atomic Layer Deposition of Noble Metals and Their Oxides. Chem. Mater. 2014, 26, 786–801. (14) Griffiths, M. B. E.; Pallister, P. J.; Mandia, D. J.; Barry, S. T. Atomic Layer Deposition of Gold Metal. Chem. Mater. 2016, 28, 44– 46. (15) Technetium, which is available primarily in short-lived, labsynthesized form, appears not to have been employed yet in ALD processes. (16) Hahn, B. P.; May, R. A.; Stevenson, K. J. Electrochemical Deposition and Characterization of Mixed-Valent Rhenium Oxide

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Films Prepared from a Perrhenate Solution. Langmuir 2007, 23, 10837–10845. (17) Zaera, F.; Somorjai, G. A. The Chemisorption of O2, CO, D2 and C2H4 over Epitaxially Grown Rhenium Crystalline Films. Surf. Sci. 1985, 154, 303–314. (18) Jiao, K. L.; Chang, L. H.; Wallace, R.; Anderson, W. A. Rhenium and Rhenium Oxide as Buffer Layers for High Tc Thin Films on Metallic Substrates. Appl. Supercond. 1995, 3, 55–60. (19) Ghanashyam Krishna, M.; Bhattacharya, A. K. Growth of Rhenium Oxide Thin Films. Solid State Commun. 2000, 116, 637– 641. (20) Murphy, N. R.; Gallagher, R. C.; Sun, L.; Jones, J. G.; Grant, J. T. Optical and Chemical Properties of Mixed-Valent Rhenium Oxide Films Synthesized by Reactive DC Magnetron Sputtering. Opt. Mater. 2015, 45, 191–196. (21) Leem, D.-S.; Lee, J.-H.; Kim, J.-J.; Kang, J.-W. Highly Efficient Tandem p-i-n Organic Light-Emitting Diodes Adopting a Low Temperature Evaporated Rhenium Oxide Interconnecting Layer. Appl. Phys. Lett. 2008, 93, 103304. (22) Cazzanelli, E.; Castriota, M.; Marino, S.; Scaramuzza, N.; Purans, J.; Kuzmin, A.; Kalendarev, R.; Mariotto, G.; Das, G. Characterization of Rhenium Oxide Films and Their Application to Liquid Crystal Cells. J. Appl. Phys. 2009, 105, 114904. (23) Yu, D.; Yang, Y.-Q.; Chen, Z.; Tao, Y.; Liu, Y.-F. Recent Progress on Thin-Film Encapsulation Technologies for Organic Electronic Devices. Opt. Commun. 2016, 362, 43–49. (24) Manabu, O.; Kumiko, F.; Matsuo, K.; Nobuyuki, I.; Hiroshi, Y. Preparation of Conductive ReO3 Thin Films. Supercond. Sci. Technol. 2002, 15, 1778–1780. (25) Elam, J. W.; Routkevitch, D.; Mardilovich, P. P.; George, S. M. Conformal Coating on Ultrahigh-Aspect-Ratio Nanopores of Anodic Alumina by Atomic Layer Deposition. Chem. Mater. 2003, 15, 3507–3517. (26) Detavernier, C.; Dendooven, J.; Pulinthanathu Sree, S.; Ludwig, K. F.; Martens, J. A. Tailoring Nanoporous Materials by Atomic Layer Deposition. Chem. Soc. Rev. 2011, 40, 5242–5253. (27) Kim, I. S.; Borycz, J.; Platero-Prats, A. E.; Tussupbayev, S.; Wang, T. C.; Farha, O. K.; Hupp, J. T.; Gagliardi, L.; Chapman, K. W.; Cramer, C. J.; Martinson, A. B. F. Targeted Single-Site MOF Node Modification: Trivalent Metal Loading via Atomic Layer Deposition. Chem. Mater. 2015, 27, 4772–4778. (28) Gallington, L. C.; Kim, I. S.; Liu, W.-G.; Yakovenko, A. A.; Platero-Prats, A. E.; Li, Z.; Wang, T. C.; Hupp, J. T.; Farha, O. K.; Truhlar, D. G.; Martinson, A. B. F.; Chapman, K. W. Regioselective Atomic Layer Deposition in Metal–Organic Frameworks Directed by Dispersion Interactions. J. Am. Chem. Soc. 2016, 138, 13513–13516. (29) Rimoldi, M.; Bernales, V.; Borycz, J.; Vjunov, A.; Gallington, L. C.; Platero-Prats, A. E.; Kim, I. S.; Fulton, J. L.; Martinson, A. B. F.; Lercher, J. A.; Chapman, K. W.; Cramer, C. J.; Gagliardi, L.; Hupp, J. T.; Farha, O. K. Atomic Layer Deposition in a Metal–Organic Framework: Synthesis, Characterization, and Performance of a Solid Acid. Chem. Mater. 2017, 29, 1050–1068. (30) Rimoldi, M.; Gallington, L. C.; Chapman, K. W.; MacRenaris, K.; Hupp, J. T.; Farha, O. Catalytically Active Silicon Oxide Nanoclusters Stabilized in a Metal–Organic Framework. Chem. Eur. J. 2017, 23, 8532–8536. (31) O’Neill, B. J.; Jackson, D. H. K.; Lee, J.; Canlas, C.; Stair, P. C.; Marshall, C. L.; Elam, J. W.; Kuech, T. F.; Dumesic, J. A.; Huber, G. W. Catalyst Design with Atomic Layer Deposition. ACS Catal. 2015, 5, 1804–1825. (32) Lu, J.; Elam, J. W.; Stair, P. C. Atomic Layer Deposition— Sequential Self-Limiting Surface Reactions for Advanced Catalyst “Bottom-Up” Synthesis. Surf. Sci. Rep. 2016, 71, 410–472. (33) Ghampson, I. T.; Sepulveda, C.; Garcia, R.; Fierro, J. L. G.; Escalona, N. Carbon Nanofiber-Supported ReOx Catalysts for the Hydrodeoxygenation of Lignin-Derived Compounds. Catal. Sci. Technol. 2016, 6, 4356–4369. (34) Hong, U. G.; Park, H. W.; Lee, J.; Hwang, S.; Yi, J.; Song, I. K. Hydrogenation of Succinic Acid to Tetrahydrofuran (THF) over Rhenium Catalyst Supported on H2SO4-Treated Mesoporous Carbon. Appl. Catal. A 2012, 415, 141–148.


Page 9 of 10

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(35) She, X.; Kwak, J. H.; Sun, J.; Hu, J.; Hu, M. Y.; Wang, C.; Peden, C. H. F.; Wang, Y. Highly Dispersed and Active ReOx on Alumina-Modified SBA-15 Silica for 2-Butanol Dehydration. ACS Catal. 2012, 2, 1020–1026. (36) Hamtil, R.; Žilková, N.; Balcar, H.; Čejka, J. Rhenium Oxide Supported on Organized Mesoporous Alumina — A Highly Active and Versatile Catalyst for Alkene, Diene, and Cycloalkene Metathesis. Appl. Catal. A 2006, 302, 193–200. (37) Phongsawat, W.; Netiworaruksa, B.; Suriye, K.; Praserthdam, P.; Panpranot, J. Effect of SiO2–Al2O3 Composition on the Catalytic Performance of the Re2O7/SiO2–Al2O3 Catalysts in the Metathesis of Ethylene and 2-Pentene for Propylene Production. Catal. Lett. 2012, 142, 1141–1149. (38) Lacheen, H. S.; Cordeiro, P. J.; Iglesia, E. Isolation of Rhenium and ReOx Species within ZSM5 Channels and their Catalytic Function in the Activation of Alkanes and Alkanols. Chem. Eur. J. 2007, 13, 3048–3057. (39) Lacheen, H. S.; Cordeiro, P. J.; Iglesia, E. Structure and Catalytic Function of Re-Oxo Species Grafted onto H-MFI Zeolite by Sublimation of Re2O7. J. Am. Chem. Soc. 2006, 128, 15082–15083. (40) Mol, J. C. Olefin Metathesis over Supported Rhenium Oxide Catalysts. Catal. Today 1999, 51, 289–299. (41) Sécordel, X.; Yoboué, A.; Cristol, S.; Lancelot, C.; Capron, M.; Paul, J.-F.; Berrier, E. Supported Oxorhenate Catalysts Prepared by Thermal Spreading of Metal Re0 for Methanol Conversion to Methylal. J. Solid State Chem. 2011, 184, 2806–2811. (42) Yuan, Y.; Iwasawa, Y. Performance and Characterization of Supported Rhenium Oxide Catalysts for Selective Oxidation of Methanol to Methylal. J. Phys. Chem. B 2002, 106, 4441–4449. (43) Herrmann, W. A.; Kratzer, R. M.; Fischer, R. W. Alkylrhenium Oxides from Perrhenates: A New, Economical Access to Organometallic Oxide Catalysts. Angew. Chem., Int. Ed. 1997, 36, 2652–2654. (44) Riha, S. C.; Libera, J. A.; Elam, J. W.; Martinson, A. B. F. Design and Implementation of an Integral Wall-Mounted Quartz Crystal Microbalance for Atomic Layer Deposition. Rev. Sci. Inst. 2012, 83, 094101. (45) de Rouffignac, P.; Gordon, R. G. Atomic Layer Deposition of Praseodymium Aluminum Oxide for Electrical Applications. Chem. Vap. Dep. 2006, 12, 152–157. (46) Aaltonen, T.; Nilsen, O.; Magrasó, A.; Fjellvåg, H. Atomic Layer Deposition of Li2O–Al2O3 Thin Films. Chem. Mater. 2011, 23, 4669–4675. (47) Wu, Y.; Potts, S. E.; Hermkens, P. M.; Knoops, H. C. M.; Roozeboom, F.; Kessels, W. M. M. Enhanced Doping Efficiency of Al-Doped ZnO by Atomic Layer Deposition Using Dimethylaluminum Isopropoxide as an Alternative Aluminum Precursor. Chem. Mater. 2013, 25, 4619–4622. (48) Atomic layer deposition of HfxAlyCz as a Work Function Material in Metal Gate MOS Devices. J. Vac. Sci. Technol. A 2013, 32, 01A118. (49) Jinjuan, X.; Yuqiang, D.; Liyong, D.; Junfeng, L.; Wenwu, W.; Chao, Z. Growth Mechanism of Atomic-Layer-Deposited TiAlC Metal Gate Based on TiCl4 and TMA Precursors. Chin. Phys. B 2016, 25, 037308. (50) Jinjuan Xianga; Tingting Lia; Xiaolei Wanga; Liyong Dub; Yuqiang Dingb; Wenwu Wanga; Junfeng Lia; Zhaoa, C. Thermal Atomic Layer Deposition of TaAlC with TaCl5 and TMA as Precursors. ECS J. Solid State Sci. Technol. 2016, 5, P633–P636. (51) QCM measurements were conducted simultaneously next to the inlet and outlet of the deposition chamber. We observed small

differences in mass gain values between inlet and outlet, and the full set of data is reported in the Supporting Information. (52) A positive y-intercept (even though small) is most probably related to an experimental error or to small deviation from linearity in the first few deposition cycles. (53) The Re : Al ratio of 1 : 1.8 was determined from a film prepared using AB cycles entailing 3 ReO3Me doses, to ensure monolayer saturation in the A cycle. (54) See Supporting Information for more details. (55) Al 2p binding energy was found to be 74.6 eV, see Supporting Information for details. (56) Komiyama, M.; Ogino, Y.; Akai, Y.; Goto, M. X-Ray Photoelectron Spectroscopic Studies of Unsupported and Supported Rhenium Using Argon-Ion Bombardment. J. Chem. Soc., Farad. Trans. 2 1983, 79, 1719–1728. (57) Given the very weak intensity of the Re(VI) component (figure 6b, blue), we cannot exclude its presence also in the top layer of the film (Figure 6a). (58) Depth profile also suggests that carbon impurities might be present in the film. (59) Spronk, R.; Andreini, A.; Mol, J. C. Deactivation of Rhenium-Based Catalysts for the Metathesis of Propene. J. Mol. Cat. 1991, 65, 219–235. (60) Mondloch, J. E.; Bury, W.; Fairen-Jimenez, D.; Kwon, S.; DeMarco, E. J.; Weston, M. H.; Sarjeant, A. A.; Nguyen, S. T.; Stair, P. C.; Snurr, R. Q.; Farha, O. K.; Hupp, J. T. Vapor-Phase Metalation by Atomic Layer Deposition in a Metal–Organic Framework. J. Am. Chem. Soc. 2013, 135, 10294–10297. (61) Yang, D.; Odoh, S. O.; Wang, T. C.; Farha, O. K.; Hupp, J. T.; Cramer, C. J.; Gagliardi, L.; Gates, B. C. Metal–Organic Framework Nodes as Nearly Ideal Supports for Molecular Catalysts: NU-1000- and UiO-66-Supported Iridium Complexes. J. Am. Chem. Soc. 2015, 137, 7391–7396. (62) Gutov, O. V.; Hevia, M. G.; Escudero-Adan, E. C.; Shafir, A. Metal–Organic Framework (MOF) Defects under Control: Insights into the Missing Linker Sites and Their Implication in the Reactivity of Zirconium-Based Frameworks. Inorg. Chem. 2015, 54, 8396–8400. (63) Manna, K.; Ji, P.; Lin, Z.; Greene, F. X.; Urban, A.; Thacker, N. C.; Lin, W. Chemoselective Single-Site Earth-Abundant Metal Catalysts at Metal–Organic Framework Nodes. Nat. Commun. 2016, 7, 12610. (64) Zhang, T.; Manna, K.; Lin, W. Metal–Organic Frameworks Stabilize Solution-Inaccessible Cobalt Catalysts for Highly Efficient Broad-Scope Organic Transformations. J. Am. Chem. Soc. 2016, 138, 3241–3249. (65) Bai, Y.; Dou, Y.; Xie, L.-H.; Rutledge, W.; Li, J.-R.; Zhou, H.-C. Zr-Based Metal–Organic Frameworks: Design, Synthesis, Structure, and Applications. Chem. Soc. Rev. 2016, 45, 2327–2367. (66) Marshall, R. J.; Forgan, R. S. Postsynthetic Modification of Zirconium Metal–Organic Frameworks. Eur. J. Inorg. Chem. 2016, 27, 4310–4331. (67) Rimoldi, M.; Howarth, A. J.; DeStefano, M. R.; Lin, L.; Goswami, S.; Li, P.; Hupp, J. T.; Farha, O. K. Catalytic Zirconium/Hafnium-Based Metal–Organic Frameworks. ACS Catal. 2017, 7, 997–1014. (68) At the conversion level of 40 % traces of C4 dimerization products were detected.



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