Electrochemical Film Deposition of the Zirconium MetalâOrganic

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Electrochemical Film Deposition of the Zirconium Metal-Organic Framework UiO-66 and Application in Miniaturized Sorbent Trap Ivo Stassen, Mark J Styles, Tom R.C. Van Assche, Nicolo Campagnol, Jan Fransaer, Joeri F.M. Denayer, Jin-Chong Tan, Paolo Falcaro, Dirk E. De Vos, and Rob Paolo Ameloot Chem. Mater., Just Accepted Manuscript • DOI: 10.1021/cm504806p • Publication Date (Web): 16 Feb 2015 Downloaded from http://pubs.acs.org on February 18, 2015

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Chemistry of Materials

Electrochemical Film Deposition of the Zirconium Metal-Organic Framework UiO-66 and Application in Miniaturized Sorbent Trap ‡

†

‡

Ivo Stassen, Mark Styles,¶ Tom Van Assche,§ Nicolò Campagnol, Jan Fransaer, Joeri Denayer,§ † † Jin-Chong Tan, ⊥ Paolo Falcaro,¶ Dirk De Vos and Rob Ameloot*, †

Department of Microbial and Molecular Systems, Centre for Surface Chemistry and Catalysis, KU Leuven – University of Leuven, Kasteelpark Arenberg 23, B-3001 Leuven, Belgium. ¶

CSIRO Manufacturing Flagship, Clayton, Victoria 3168, Australia.

‡

Department of Metallurgy and Materials Engineering, KU Leuven – University of Leuven, Kasteelpark Arenberg 44, B-3001 Leuven, Belgium §

Department of Chemical Engineering, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussel, Belgium

⊥

Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, United Kingdom

KEYWORDS metal-organic framework, film, zirconium, UiO-66, electrodeposition, miniaturized device, sorbent ABSTRACT: Film deposition is an enabling technology for integration of novel functional materials into real-world practical applications. We report both the anodic and cathodic electrochemical film deposition of UiO-66, a prototype of highly stable zirconium based metal-organic frameworks (MOFs), using zirconium foil as the only metal source. The fundamentally different film formation mechanisms at the cathode and anode result in a significantly different coating adhesion strength, mainly due to the formation of an oxide film serving as bridging layer at the anode. The patterned deposition capability of the electrochemical method enables the straightforward integration of UiO-66 as a sorbent film in a miniaturized sorbent trap for on-line analytical sampling and concentration of dilute volatile organic compounds (VOCs).

INTRODUCTION Metal-organic frameworks (MOFs), a class of hybrid nanoporous crystalline materials, have been studied extensively in the last decade because of their high specific surface area and their unique structural and chemical tunability.1 For applications such as gas adsorption and catalysis, MOFs are mainly used as bulk materials in the form of powders. For other applications, suitable film deposition and patterning techniques are enabling technologies.2–6 Various film deposition strategies have been reported, mostly for MOFs forming under mild conditions. However, considerable interest exists in MOFs that require harsher crystallization conditions, such as MOFs based on high valent metal ions, as these can have superior chemical and thermal stabilities. One typical example is the Zr(IV) based Zr6O4(OH)4(BDC)6 framework, termed UiO-66.7–9 Solvothermal synthesis,10–12 crystal structure13,14 and various properties and potential applications in e.g., catalysis,15 photocatalysis,16 supercapacitors,17 battery technology,18 and microextraction19 have recently been studied for UiO-66 and its isoreticular analogues. However, reports on film deposition of UiO-66 are scarce and, apart from few exceptions,20 limited to deposition of ex situ prepared particles.17,21–23 Ex situ deposited films are, however, never intergrown and adhesion to the substrate

is often limited.24 In situ deposition generally offers an improvement over these shortcomings. Electrochemical MOF deposition has been proposed as a promising and industrially relevant approach for in situ deposition and patterning on conductive surfaces.2 Two fundamentally different electrochemical MOF deposition mechanisms have been reported: anodic deposition and cathodic deposition. In anodic deposition, MOF film formation occurs on a metal anode contacted with a ligand solution as a result of the release of a critical concentration of metal ions by anodic dissolution.25,26 In cathodic deposition, on the other hand, a solution containing a ligand, metal ions and a so-called probase is contacted with a cathodic surface. Film deposition in this case is the result of an increase in pH near the cathodic surface, where electrochemical reduction of the probase results in local base generation, and subsequent ligand deprotonation inducing MOF formation.27,28 Even though anodic deposition of Cu(II),25,29–31 Fe(III),32 Gd(III),33 Tb(III)33 and Zn(II)34 MOFs and cathodic deposition of Zn(II)27, Tb(III)35 and Eu(III)36 MOFs have been demonstrated, no reports exist on the electrochemical deposition of higher valence cation frameworks. While the oxophilic nature of Zr(IV) is a main contributor to UiO-66’s

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Figure 1. Scheme of the anodic and cathodic electrochemical deposition mechanisms demonstrated in this paper. high stability,7 it also implies more challenging electrochemistry. The incorporation of Zr(IV) ions in a MOF lattice upon anodic dissolution of a zirconium electrode is in direct competition with oxide formation, more so than for the previously mentioned metals.37 Furthermore, zirconium passivation by oxide film formation on exposed metallic surfaces results in a high resistance to further oxidation, even superior to the corrosion resistance of stainless steel.38,39 Similar difficulties exist at the cathode, where deposition of zirconium hydroxide is expected via reaction of dissolved zirconium ions with cathodically generated hydroxide ions.37 Although the conversion of metal oxide and hydroxide films to MOF coatings has been demonstrated,40–42 this reaction does not seem to be feasible for Zr(IV)-based (hydr)oxides.43 These considerations underline the challenges of identifying the conditions suitable for electrochemical deposition of Zr(IV) based MOFs. Herein, we demonstrate both the anodic and cathodic film deposition of UiO-66 and related Zr(IV) based MOFs (Figure 1). Zirconium oxide film formation on the anode, as well as the rate of cathodic deposition and the UiO-66 film morphology are controlled via a synthesis modulation approach using acetic acid. The identification of this set of deposition conditions enables the deposition of a range of Zr-based MOFs on different conductive substrates. Film adhesion on the anode and cathode is compared by a nanoindenter scratching study. Film integration in a miniaturized flow-through device for sampling and concentration of volatile organic compounds (VOCs) is also demonstrated.

EXPERIMENTAL SECTION Chemicals and materials. 1,4-benzenedicarboxylic acid (Sigma-Aldrich, 98%), nitric acid (Fisher Scientific , 68%), acetic acid (Acros Organics, 99%), toluene (SigmaAldrich, 99.8%) and squaric acid (Sigma-Aldrich, 99%)

were used as received without further purification. Zirconium foil (0.25 mm thick, ABCR, 99.8%), titanium foil (1.0 mm thick, ABCR, 99.2%), titanium nitride on silicon wafer (sputtered by physical vapor deposition), were cleaved (10 mm x 30 mm) and rinsed with acetone before use as electrode materials. 2,2′-Dinitrobiphenyl-4,4′-dicarboxylic acid was prepared from dimethyl biphenyl-4,4′dicarboxylate (Sigma-Aldrich, 99%) according to a previously published procedure,44 followed by hydrolysis with NaOH in ethanol/water and acidification with HCl. Electrochemical deposition setup. Film deposition was performed in an electrolytic cell consisting of a power supply unit (Thurlby Thandar Instruments TS3021S), a screw cap glass bottle (Duran® pressure plus+) containing a synthesis solution and two electrodes connected to the power source with stainless steel clips (perforating the screw cap). Heating was supplied by an oil bath. The parallelly mounted electrodes were immersed approximately 20 mm deep in solution, 15 mm from each other. Note that due to gas evolution during synthesis, an air-tight cell is not recommended unless pressure resistance is ensured. High temperature, high pressure (HT-HP) synthesis was performed in our previously reported HT-HP electrolytic cell.32 Film deposition procedure. 415 mg 1,4benzenedicarboxylic acid (BDC) was dissolved in 25 ml dimethylformamide (DMF). To this solution, 300 µl nitric acid 68%, 90 µl water and 715/1430/7150 µl glacial acetic acid (AA) were added. The final molar ratio of the synthesis solution was BDC : HNO3 : H2O : AA : DMF = 1 : 2 : 4 : 5/10/50 : 130. The corresponding final AA concentration was respectively 0.5, 1 or 5 M. For the preparation of (NO2)2-UiO-67, a similar solution was used except for replacing BDC by 825 mg 2,2′-dinitrobiphenyl-4,4′dicarboxylic acid. For the preparation of ZrSQU, a previously reported synthesis solution was used.45 Zirconium foil was used both as anode and cathode material unless stated otherwise. Before applying a voltage to the elec-


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trodes, the synthesis solution was heated to 383 K. Film deposition was performed at this temperature by applying a current of 80 mA for a specified time. A potential difference between 6 and 9 V was typically applied to maintain a constant current density. In the absence of nitric acid, no significant current could be triggered, not even at 30 V, which is the maximum potential of the power supply unit. Gas evolution could be observed (by eyes) at both electrodes during the deposition. After deposition the synthesis solution was cooled and the electrodes were removed, soaked subsequently in DMF and methanol and dried under air flow. The side of the anode facing the cathode, and vice versa, was used for all analyses. Application in miniaturized sorbent trap. Device integration was performed in a similar way as our previously reported procedure.46 In summary, (1) polyether ether ketone (PEEK) adhesive tape (500 µm thick) was patterned with a meandering channel (171 mm length, 2 mm width) by precision milling and applied to the zirconium foil substrate. (2) The assembly was mounted in a PTFE frame with a cutout at the front to exclude reaction at the backside of the foil. Anodic film deposition was performed on the zirconium surface exposed through the PEEK pattern for 120 min (0.5 M AA concentration). After washing and drying, the sample was activated by evacuation in a vacuum oven at 373 K for 4 h. (3) Subsequently, the assembly was mounted in a home-built device designed to enable gas flow through the patterned PEEK channels while controlling the channel temperature via heating of the zirconium foil. Downstream of the device, organics were detected using a flame ionization detector (FID). Before the adsorption experiments, the device was flushed overnight with 10 mlN min-1 He at 343 K. Next, vaporized toluene in He (200 ppmv, 10 mlN min-1) was introduced into the setup via a temperature-controlled saturator in combination with a set of mass flow controllers. After equilibration at 308K, as indicated by FID, toluene desorption was monitored upon quickly heating the device to 343 K through the integrated heating circuit or through heating in a fast-heating (100 K min-1) convection oven. Instrumentation. Scanning electron microscopy (SEM) images were recorded using a Philips XL30 FEG. For cross-sectional imaging, the electrodes were cut. The samples were sputtered with Pt before analysis. X-ray diffraction (XRD) patterns were recorded on a STOE STADI MP instrument in Bragg–Brentano mode (2θ – θ geometry; Cu Kα1) using a linear position-sensitive detector; step width 0.5° 2θ, scan rate= 1520 s per step (2θ=5– 20°; Δ2θ=0.01°). Powder patterns were recorded on a STOE STADI P Combi instrument in Debye Scherrer geometry (Cu Kα1) using an IP position-sensitive detector (2θ=0–60°; Δ2θ=0.03°). Background-corrected XRD patterns were normalized before plotting. ATR-FTIR spectra were recorded on an Agilent Technologies Varian 670 FTIR spectrometer coupled to a Varian 620 infrared microscope equipped with a slide-on ATR tip. Nanoindenter scratch experiments31 were performed on an MTS Nanoindenter XP equipped with Berkovich diamond

indenter tip. The substrate with coated surface was laterally translated under the indenter tip for a total scratch length of 100 µm at a speed of 5 µm s-1 (0° or 180° tip orientation). The normal load was progressively increased from 0 to 10 mN at a loading rate of 0.5 mN s-1 during a ramp load run. During a pass-and-return wear test, 10 cycles, each consisting of a pass in 0° direction and a return in 180° direction, were performed at a normal load of 20 mN. Toluene adsorption isotherms were measured using a Micromeritics 3Flex 3500 physisorption instrument equipped with a thermostatic vapor source container. A reference (powder) sample was prepared following a previously reported solvothermal procedure.15 The samples were degassed before measurement at 343 K under vacuum (10-2 mbar) for 4 h.

RESULTS AND DISCUSSION Anodic deposition. It has been reported that the nucleation rate during the solvothermal synthesis of UiO-66 is positively influenced by the presence of aqueous acids10. However, this beneficial effect was recently attributed to the added water, which increases the Zr6O4(OH)4 cluster formation rate, while the acid itself slightly decreases the nucleation rate by hampering ligand deprotonation. Presence of the strong acid nevertheless still leads to an increased yield and a higher crystallinity of the formed UiO66.11 For electrochemical synthesis, we decided to add nitric acid and additional water instead of hydrochloric acid which is typically used; in this way, the potential formation of toxic chlorine gas was prevented. At the same time, the nitrate anions function as probase in the cathodic electrochemical deposition (vide infra). In addition, nitric acid also serves as an electrolyte during the electrochemical procedure. Film deposition on the anode was studied in the presence of different concentrations (0.5, 1 and 5 M) of acetic acid (AA). In solvothermal UiO-66 synthesis, synthesis modulation by addition of AA has been shown to increase the amount of linker defects and concomitantly the pore volume and surface area,47 as well as to improve crystallinity and provide control over the crystallite size and morphology.12 For anodic film deposition, an increase in AA modulator concentration from 0.5 to 1 M changes the film morphology from loosely stacked (2-5 µm) aggregates of nanocrystals, towards smaller (< 1 µm) and more densely packed aggregates, thereby significantly increasing the film smoothness (Figure 2). A further increase to 5 M AA results in larger (up to 750 nm) well-defined and separated octahedral nanocrystals. These results show that not only the crystallite size, but also the film morphology can be controlled by applying the synthesis modulation approach.



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Figure 2. SEM images of (a) pristine zirconium foil and of zirconium foil substrate after 30 min of UiO-66 anodic deposition in the presence of (b) 0.5, (c) 1 and (d) 5 M acetic acid. Scale bars 5 µm; insets 500 nm. Figure 3 shows ex situ measured XRD patterns after different synthesis times. While the deposition of highly crystalline UiO-66 is observed at all AA concentrations after 30 minutes, the anodic deposition process and the resulting films are influenced in two additional ways. Firstly, the broad diffraction peaks corresponding to orthorhombic and monoclinic zirconium oxide (see Figure S7 for detailed identification), resulting from metal passivation, increase in intensity relative to the zirconium peaks at higher AA concentrations. This shows that, due to the increased competition between modulator and ligand at higher AA concentrations, the MOF nucleation rate is suppressed in favor of oxide formation. This observation may also indicate that formed Zr(IV) acetate species contribute towards zirconium oxide deposition at the anode while other possible Zr(IV) species (such as terephthalate and nitrate) do not, or to a lesser extent. A possible explanation is the low stability of acetate towards electrochemical oxidation,48,49 resulting in the release of Zr(IV) species susceptible to olation reactions in the proximity of the anode. Secondly, the competition between ligand and modulator for complexation of Zr(IV) decreases the apparent deposition rate of UiO-66, as indicated by the decreasing intensity of the UiO-66 peaks relative to the substrate peaks. The decreased growth rate at higher AA concentrations is also indicated by a clear difference in resulting UiO-66 film thickness, ranging from less than 1 µm to more than 10 µm for respectively 5 M and 0.5 M AA (Figures S3-5). This rate decrease is similar to the slower crystallization observed during solvothermal synthesis in the presence of monocarboxylic modulators.50 Similar to increasing the AA concentration, lowering the water content of the synthesis solution also leads to a decrease in deposition rate. (Figure S8), which is explained by the role of water as oxygen source in the formation of the Zr6O4(OH)4 cluster.

Figure 3. XRD patterns of pristine zirconium foil and of zirconium foil substrate after UiO-66 anodic deposition for 10 and 30 minutes in the presence of 0.5, 1 and 5 M acetic acid (AA). Simulated diffraction patterns are shown for Zr and UiO-66; the positions of the zirconium oxide peaks are indicated by the black diamonds. The anode color progressively turned from grey to black, consistent with the reported formation of a passive zirconium oxide film.51 The formed MOF film was only visible after drying, depending on the thickness, as a colorful interference pattern or a white film. To demonstrate the applicability of the electrochemical deposition method for other Zr based MOFs, the isoreticular materials (NO2)2UiO-67, containing 2,2′-dinitrobiphenyl-4,4′dicarboxylate linkers and ZrSQU, containing squarate linkers, were also synthesized as thin films (see supporting information). Cathodic deposition. Although our initial focus was the development of an anodic deposition procedure, the observation of simultaneous cathodic deposition also attracted our interest. Whereas film deposition on the cathode occurred only to a minor extent in the presence of 0.5 M AA, it was clearly observed in the presence of 1 and 5 M AA. Figure 4 shows SEM images recorded after 30 minutes of UiO-66 cathodic deposition on zirconium foil. This observation indicates that AA, via complexation of Zr(IV) released at the anode, acts as a carrier species, enabling transport of Zr(IV) species through the solution to the counter-electrode for cathodic deposition. As increased competition for complexation of released Zr(IV) ions at higher AA concentrations leads to less anodic deposition of UiO-66 (vide supra), the concentration of dissolved zirconium species will evidently increase, eventually resulting in increased deposition at the cathode.


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Figure 4. SEM images of UiO-66 film after 30 min of cathodic deposition on zirconium foil in the presence of (a) 1 M and (b) 5 M acetic acid. Scale bars 2 µm. Comparison of the films deposited in the presence of 1 and 5 M acetic acid clearly shows that the effect of modulation on crystal size is similar to that observed for the anodic process. The film that is cathodically deposited in the presence of 5 M AA is thicker and the surface coverage higher than for the corresponding anodic film (Figure 2d). This confirms that an increase in modulator concentration can switch the deposition process from mainly anodic towards cathodic deposition. The most distinctive feature of cathodic deposition is that UiO-66 can be deposited on any conductive substrate by means of this approach. XRD (Figure 5) and ATR-FTIR (Figure s9) confirm that UiO-66 coatings were successfully formed on cathodes with different properties and compositions, such as metallic zirconium, metallic titanium and titanium nitride on top of a silicon wafer. Moreover, no diffraction peaks corresponding to zirconium (hydr)oxides are observed. While the films deposited on zirconium and titanium show well-resolved UiO-66 diffraction peaks, only a broad signal can be seen for the film deposited on the smooth titanium nitride-coated wafers (Figure 5). This might indicate the need for surface anchoring points or a degree of surface-specificity of the base generation reaction.

Figure 5. XRD of different substrates after UiO-66 cathodic deposition for 30 minutes in the presence of 1 M acetic acid (AA). Top to bottom: zirconium foil, titanium foil and titanium nitride thin film on silicon wafer. All peaks above 30° 2θ correspond to the respective substrates.

Figure 6. SEM images of UiO-66 films after Berkovich indenter scratching experiments. Top: ramp load profile and corresponding scratch images for (a) an anodically deposited film and (b) a cathodically deposited film. Bottom: 10 cycles pass-and-return wear test profile and corresponding scratch images for (c) an anodically deposited film and (d) a cathodically deposited film. Both films were deposited for 30 minutes (1 M AA). Scale bars 10 µm. Mechanical properties. Dissimilarity in mechanical properties for the anodically and cathodically deposited films is expected based on a distinct difference in microscopic appearance. While cathodically deposited films show mud cracking motives due to poor film cohesion during drying (enhanced by beam damage during SEM), this phenomenon was never observed for anodically deposited films. Scratching experiments with a Berkovich indenter tip on films deposited for 30 minutes in the presence of 1 M AA show a clear difference in mechanical response to an applied load (Figure 6). Anodically deposited films are compressed while staying attached to the substrate. For the cathodically deposited film, however, clear delamination accompanied by total detachment of the film is observed under identical test conditions. This difference in adhesion indicates that for the anodically deposited film, the zirconium oxide film functions as a bridging layer between the metallic substrate and the MOF film, thereby conferring improved interfacial mechanical strength. This result is most promising from a mechanical viewpoint,52 towards fabrication of damagetolerant MOF thin films to enable practical applications.



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Figure 7. Miniaturized sorbent trap for vapor sampling and concentration. (a) Exploded view of the custom-built vapor sampling device: (1) front cover with gas flow connections; (2) sorbent plate; (3) gasket with cutout heat-transfer liquid circuit; (4) gasket; (5) back cover with heat-transfer fluid connections. (b) Photograph of sorbent plate with anodically deposited UiO-66 film. (c) Detector signal during thermal desorption of toluene from the UiO-66 vapor sampling device. Desorption is initiated at td = 4 min. Black curves: heating supplied by integrated heater, blue curves: heating supplied by convection oven heating at a rate of 100 K min-1, grey: reference measurement without UiO-66 film. Applied temperature profiles for thermal desorption are represented by the dashed lines. (d) Toluene vapor adsorption isotherms measured at 308 K and 343 K on sorbent plate. The inset shows the decrease in adsorption capacity at feed concentration of the UiO66 film when heated from 308 K to 343 K. Miniaturized sorbent trap integration. UiO-66 was anodically deposited as a sorbent film in the meandering channels of a custom-designed cartridge for sampling of volatile organics from gas phase (Figure 7a). The cartridge was fixed in a tailor-made device provided with connections for gas flow through the meandering channel and an integrated heater (Figure 7b). The performance of this device in sampling and concentrating VOCs was evaluated using toluene as a model compound. In a first step, a He stream (10 ml min-1) containing toluene traces (200 ppmv) was passed through the device until equilibration. At a specific time, the device was quickly heated while maintaining the feed as the carrier gas stream, and the outlet stream was analyzed. This mode of operation, combining active online sampling with analytical thermal desorption, is widely used in sorbent trap and solid-phase extraction systems for vapor sampling.53 In a first experiment, thermal desorption was induced by placing the device in a fast-heating convection oven. Figure 7c (blue curve) shows the normalized toluene concentration in the outlet stream before and after a programmed temperature increase of 35 K at td= 4 min. The toluene enrichment in the outlet stream reaches a maximum concentration of 3.7 times the inlet concentration, or 740 ppmv, approximately 160 seconds after td. Integration of the enrichment peak however shows a net release of toluene corresponding to 510 detector counts during the first 15 minutes of desorption, indicating that the peak height can be significantly increased by improving the desorption kinetics. To increase the desorption rate, an integrated heater was used to induce the same 35 K temperature increase directly at the zirconium metal backside of the sorbent plate (Figure 7a). Enrichment of toluene in the outlet stream can be observed almost instantaneously at td (Figure 7c,

black curve). All other conditions being equal, these faster desorption kinetics can be attributed to the integration of the UiO-66-coated zirconium film with the integrated heater in the miniaturized system. An initial maximum toluene concentration of 2470 ppmv (13.7 times the inlet concentration) was observed. Integration of the enrichment peak shows a net release of toluene corresponding to 265 detector counts in the first minute of desorption. Further enhancement of this concentration factor, while beyond the scope of this paper, might be achieved by implementation of a downstream focusing trap or by further optimization of operative conditions such as e.g., the carrier gas stream (see supporting information) and the temperature profile during thermal desorption. Figure 7d shows adsorption isotherms measured for toluene on the sorbent plate at the working conditions of the thermal desorption experiments. The applied temperature increase of 35 K at 200 ppmv (= 0.2 mbar) leads towards a decrease in adsorption capacity at equilibrium from 0.83 µmol cm-2 to 0.39 µmol cm-2. This makes evident that further optimization of the temperature program towards full desorption has the potential to roughly double the performance of the device. Furthermore, the steeper slope of the isotherms at lower pressures indicates that relative enrichment in the material will increase towards even lower concentrations, once more underlining the potential of UiO-66 as a sorbent for sampling and concentration of traces of volatile organics. An approximate film coverage of 3.2-3.3 mg cm-2 was calculated from the comparison of the toluene adsorption isotherm for the sorbent trap and a UiO-66 powder sample (Figure S22). Taking into account the crystallographic density of UiO-66, this corresponds to a film thickness of approximately 27-28 µm. As the film consists of rather


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loosely stacked aggregates (vide supra) and because of the relatively high linear velocity (17 cm s-1) and strain forces due to thermal expansion and contraction, gradual detachment of the adsorbent layer by the gas flow was initially anticipated. Nevertheless, it is striking to see that reproducibility tests showed consistent device performance over a large number of runs (Figure S24). The excellent adhesion of films deposited under anodic conditions can be attributed to the zirconium oxide bridging layer.

CONCLUSION The chemical window for both the anodic and cathodic electrochemical deposition of the highly stable Zr(IV) based MOF UiO-66 and its isoreticular analogues has been identified and elucidated in this work. Interestingly, synthesis modulation not only allows tuning of the crystallite size and film morphology, but at the same time provides control over the prevailing deposition mechanism. Whereas anodic deposition results in superior adhesion of the MOF layer onto the metallic zirconium substrate due to the formation of an oxide bridging layer, cathodic deposition has the advantage of broad substrate flexibility. The versatility of the electrochemical deposition method may lead towards new applications for MOFs based on high-valent metal ions. The possibility for integrating such materials in functional devices is demonstrated by the construction and operation of a miniaturized sorbent trap based on the selective adsorption characteristics of an electrochemically deposited UiO-66 coating. Our miniaturized sorbent trap demonstration shows that device integration, in this case permitted by the development of an electrochemical deposition method, strongly contributes to an increased functional material performance.

Policy Office (BELSPO) for support in IAP project 7/05 and to KU Leuven for CASAS Methusalem funding. R. A. thanks KU Leuven for a start-up grant. I. S. thanks Research Foundation – Flanders (FWO) for a Ph.D. fellowship. T. V. A. thanks IWT for a Ph.D. grant. The support of E. Gobechiya during xray diffraction experiments is much appreciated. We thank Imec Leuven for supplying TiN substrates.

ABBREVIATIONS AA, acetic acid; ATR-FTIR, attenuated total reflection Fourier transform infrared spectroscopy; BDC, 1,4benzenedicarboxylic acid; DMF, dimethylformamide; FID, flame ionization detector; HT-HP, high temperature, high pressure; ppmv, parts per million by volume; PEEK, polyether ether ketone; SEM, scanning electron microscopy; VOC, volatile organic compound; XRD, x-ray diffraction.

REFERENCES (1)

Furukawa, H.; Cordova, K. E.; O’Keeffe, M.; Yaghi, O. M. Science 2013, 341, 1230444.

(2)

Falcaro, P.; Ricco, R.; Doherty, C. M.; Liang, K.; Hill, A. J.; Styles, M. J. Chem. Soc. Rev. 2014, 43, 5513.

(3)

Bétard, A.; Fischer, R. A. Chem. Rev. 2012, 112, 1055.

(4)

Stavila, V.; Talin, A. A.; Allendorf, M. D. Chem. Soc. Rev. 2014, 43, 5994.

(5)

Kreno, L. E.; Leong, K.; Farha, O. K.; Allendorf, M.; Van Duyne, R. P.; Hupp, J. T. Chem. Rev. 2012, 112, 1105.

(6)

Allendorf, M. D.; Schwartzberg, A.; Stavila, V.; Talin, A. A. Chemistry 2011, 17, 11372.

(7)

Cavka, J. H.; Jakobsen, S.; Olsbye, U.; Guillou, N.; Lamberti, C.; Bordiga, S.; Lillerud, K. P. J. Am. Chem. Soc. 2008, 130, 13850.

(8)

Kandiah, M.; Nilsen, M. H.; Usseglio, S.; Jakobsen, S.; Olsbye, U.; Tilset, M.; Larabi, C.; Quadrelli, E. A.; Bonino, F.; Lillerud, K. P. Chem. Mater. 2010, 22, 6632.

(9)

Kim, M.; Cohen, S. M. CrystEngComm 2012, 14, 4096.

(10)

Katz, M. J.; Brown, Z. J.; Colón, Y. J.; Siu, P. W.; Scheidt, K. A.; Snurr, R. Q.; Hupp, J. T.; Farha, O. K. Chem. Commun. 2013, 49, 9449.

(11)

Ragon, F.; Horcajada, P.; Chevreau, H.; Hwang, Y. K.; Lee, U.-H.; Miller, S. R.; Devic, T.; Chang, J.-S.; Serre, C. Inorg. Chem. 2014, 53, 2491.

(12)

Schaate, A.; Roy, P.; Godt, A.; Lippke, J.; Waltz, F.; Wiebcke, M.; Behrens, P. Chemistry 2011, 17, 6643.

(13)

Zhu, L.; Zhang, D.; Xue, M.; Li, H.; Qiu, S. CrystEngComm 2013, 15, 9356.

ASSOCIATED CONTENT Supporting Information. Additional SEM images and XRD patterns; ATR-FTIR spectra; deposition of isoreticular MOFs; HT-HP deposition; nanoindenter scratching profiles; miniaturized sorbent trap experimental setup, toluene adsorption isotherms, film coverage calculation and sorbent trap repeated runs. This material is available free of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION Corresponding Author

* E-mail: [email protected] Author Contributions The manuscript was written through contributions of all authors.

Notes The authors declare no competing financial interest.

ACKNOWLEDGMENT The authors are grateful to the Agency of Innovation by Science and Technology Flanders (IWT) for support in SBO project MOFShape. D. D. V. is grateful to the Belgian Science



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(14)

Valenzano, L.; Civalleri, B.; Chavan, S.; Bordiga, S.; Nilsen, M. H.; Jakobsen, S.; Lillerud, K. P.; Lamberti, C. Chem. Mater. 2011, 23, 1700.

(15)

Vermoortele, F.; Vandichel, M.; Van de Voorde, B.; Ameloot, R.; Waroquier, M.; Van Speybroeck, V.; De Vos, D. E. Angew. Chem. Int. Ed. 2012, 51, 4887.

(16)

Gomes Silva, C.; Luz, I.; Llabrés i Xamena, F. X.; Corma, A.; García, H. Chemistry 2010, 16, 11133.

(17)

Choi, K. M.; Jeong, H. M.; Park, J. H.; Zhang, Y.-B.; Kang, J. K.; Yaghi, O. M. ACS Nano 2014, 8, 7451.

(18)

Ameloot, R.; Aubrey, M.; Wiers, B. M.; Gómora-Figueroa, A. P.; Patel, S. N.; Balsara, N. P.; Long, J. R. Chemistry 2013, 19, 5533.

(19)

(20)

(21)

(22)

(23)

Shang, H.-B.; Yang, C.-X.; Yan, X.-P. J. Chromatogr. A 2014, 1357, 165. Maza, W. A.; Ahrenholtz, S. R.; Epley, C. C.; Day, C. S.; Morris, A. J. J. Phys. Chem. C 2014, 118, 14200. Lu, G.; Cui, C.; Zhang, W.; Liu, Y.; Huo, F. Chem. Asian J. 2013, 8, 69. Long, J.; Wang, S.; Ding, Z.; Wang, S.; Zhou, Y.; Huang, L.; Wang, X. Chem. Commun. 2012, 48, 11656. Hod, I.; Bury, W.; Karlin, D. M.; Deria, P.; Kung, C.-W.; Katz, M. J.; So, M.; Klahr, B.; Jin, D.; Chung, Y.-W.; Odom, T. W.; Farha, O. K.; Hupp, J. T. Adv. Mater. 2014, 26, 6295.

Page 8 of 10

(33)

Campagnol, N.; Souza, E. R.; De Vos, D. E.; Binnemans, K.; Fransaer, J. Chem. Commun. 2014.

(34)

Cheng, K.-Y.; Wang, J.-C.; Lin, C.-Y.; Lin, W.-R.; Chen, Y.A.; Tsai, F.-J.; Chuang, Y.-C.; Lin, G.-Y.; Ni, C.-W.; Zeng, Y.T.; Ho, M.-L. Dalton Trans. 2014, 43, 6536.

(35)

Wang, Y.; Chu, T.; Yu, M.; Liu, H.; Yang, Y. RSC Adv. 2014, 4, 58178.

(36)

Liu, H.; Wang, H.; Chu, T.; Yu, M.; Yang, Y. J. Mater. Chem. C 2014, 2, 8683.

(37)

Kamada, K.; Mukai, M.; Matsumoto, Y. J. Mater. Sci. 2004, 39, 5779.

(38)

Stojilovic, N.; Bender, E. T.; Ramsier, R. D. Prog. Surf. Sci. 2005, 78, 101.

(39)

Nagano, H.; Kajimura, H.; Yamanaka, K. Mater. Sci. Eng. A 1995, 198, 127.

(40)

Stassen, I.; Campagnol, N.; Fransaer, J.; Vereecken, P.; De Vos, D.; Ameloot, R. CrystEngComm 2013, 15, 9308.

(41)

Okada, K.; Ricco, R.; Tokudome, Y.; Styles, M. J.; Hill, A. J.; Takahashi, M.; Falcaro, P. Adv. Funct. Mater. 2014, 24, 1969.

(42)

Reboul, J.; Furukawa, S.; Horike, N.; Tsotsalas, M.; Hirai, K.; Uehara, H.; Kondo, M.; Louvain, N.; Sakata, O.; Kitagawa, S. Nat. Mater. 2012, 11, 717.

(43)

Unpublished work.

(24)

Shekhah, O.; Liu, J.; Fischer, R. A.; Woll, C. Chem. Soc. Rev. 2011, 40, 1081.

(44)

Ol’khovik, V. K.; Pap, a. a.; Vasilevskii, V. a.; Galinovskii, N. a.; Tereshko, S. N. Russ. J. Org. Chem. 2008, 44, 1172.

(25)

Ameloot, R.; Stappers, L.; Fransaer, J.; Alaerts, L.; Sels, B. F.; De Vos, D. E. Chem. Mater. 2009, 21, 2580.

(45)

Bueken, B.; Reinsch, H.; Reimer, N.; Stassen, I.; Vermoortele, F.; Ameloot, R.; Stock, N.; Kirschhock, C. E. A.; De Vos, D. Chem. Commun. 2014, 50, 10055.

(26)

Campagnol, N.; Van Assche, T.; Stappers, L.; Denayer, J. F. M.; Binnemans, K.; De Vos, D. E.; Fransaer, J. ECS Trans. 2014, 61, 25.

(46)

Van Assche, T. R. C.; Denayer, J. F. M. Chem. Eng. Sci. 2013, 95, 65.

(47)

Wu, H.; Chua, Y. S.; Krungleviciute, V.; Tyagi, M.; Chen, P.; Yildirim, T.; Zhou, W. J. Am. Chem. Soc. 2013, 130628083629002.

(48)

Ross, S. D.; Finkelstein, M.; Petersen, R. C. J. Am. Chem. Soc. 1964, 86, 4139.

(49)

Nonaka, H.; Matsumura, Y. J. Electroanal. Chem. 2002, 520, 101.

(50)

Wißmann, G.; Schaate, A.; Lilienthal, S.; Bremer, I.; Schneider, A. M.; Behrens, P. Microporous Mesoporous Mater. 2012, 152, 64.

(51)

Tejland, P.; Langhammer, C.; Andrén, H.-O. J. Nucl. Mater. 2010, 400, 79.

(52)

Tan, J. C.; Cheetham, A. K. Chem. Soc. Rev. 2011, 40, 1059.

(27)

Li, M.; Dincă, M. J. Am. Chem. Soc. 2011, 133, 12926.

(28)

Li, M.; Dincă, M. Chem. Sci. 2014, 5, 107.

(29)

Van Assche, T. R. C.; Desmet, G.; Ameloot, R.; De Vos, D. E.; Terryn, H.; Denayer, J. F. M. Microporous Mesoporous Mater. 2012, 158, 209.

(30)

Martinez Joaristi, A.; Juan-Alcañiz, J.; Serra-Crespo, P.; Kapteijn, F.; Gascon, J. Cryst. Growth Des. 2012, 12, 3489.

(31)

Van de Voorde, B.; Ameloot, R.; Stassen, I.; Everaert, M.; De Vos, D.; Tan, J.-C. J. Mater. Chem. C 2013, 1, 7716.

(32)

Campagnol, N.; Van Assche, T.; Boudewijns, T.; Denayer, J.; Binnemans, K.; De Vos, D.; Fransaer, J. J. Mater. Chem. A 2013, 1, 5827.


Page 9 of 10 (53)

Chemistry of Materials Woolfenden, E. J. Chromatogr. A 2010, 1217, 2674.

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