Rendering High Surface Area, Mesoporous MetalâOrganic

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Rendering High Surface Area, Mesoporous MetalOrganic Frameworks Electronically Conductive Timothy C. Wang, Idan Hod, Cornelius O. Audu, Nicolaas A. Vermeulen, SonBinh T. Nguyen, Omar K. Farha, and Joseph T. Hupp ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b16834 • Publication Date (Web): 20 Mar 2017 Downloaded from http://pubs.acs.org on March 21, 2017

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ACS Applied Materials & Interfaces

Rendering High Surface Area, Mesoporous Metal-Organic Frameworks Electronically Conductive Timothy C. Wang,1 Idan Hod,2 Cornelius O. Audu,1 Nicolaas A. Vermeulen,1 SonBinh T. Nguyen,1 Omar K. Farha,*,1,3 and Joseph T. Hupp*,1 1Department

of Chemistry, Northwestern University, Evanston, Illinois 60208, United States of Chemistry, Ben-Gurion University of the Negev, Beer Sheva, 84105, Israel 3Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah 22254, Saudi Arabia Keywords: Metal-Organic Framework, Polythiophene, Electronic Conductivity, Electropolymerization, SolventAssisted Ligand Incorporation, QCM porosity measurement. 2Department

ABSTRACT: We report the design and synthesis of a MOF-polythiophene composite that has comparable electronic conductivity to reported conductive 3-D MOFs, but with display and retention of high porosity, including mesoporosity. A robust zirconium MOF, NU-1000, was rendered electronically conductive by first incorporating, via solvent-assisted ligand incorporation (SALI), a carefully designed pentathiophene derivative at a density of one pentamer per hexa-zirconium node. Using a cast film of the intermediate composite (termed pentaSALI) on conductive glass, the incorporated oligothiophene was electrochemically polymerized to yield the conductive composite, Epoly. Depending on the doping level of the polythiophene in the composite, it can be tuned from an insulating state to a semiconduting state with conductivity of 1.3×10-7 (S cm-1), which is comparable to values reported for 3-D conductive MOFs. The porosity of the thin-film MOF-polythiophene composite was assessed using decane vapor uptake as determined by quartz crystal microgravimetry (QCM). The results indicate a porosity (pore volume) for Epoly essentially identical to that of bulk pentaSALI, and ~74% of that of unmodified NU-1000. PentaSALI, and by inference Epoly, displays both micro- and mesoporosity, and features a BET surface area of nearly 1,600 m2 g-1, i.e. substantially larger than yet reported for any other electronically conductive MOF.

INTRODUCTION Metal-Organic Frameworks (MOFs) are a class of porous, crystalline materials that are constructed using metal clusters (or ions) and organic linkers. 1-5 With careful selection of both components, often aided by computational simulation,6 the physical and chemical properties can be tuned for specific candidate applications7-8 such as gas storage9-10 and separation,11 catalysis,12-13 sensing,14-15 drug delivery16 and solar energy conversion.17 MOFs, however, usually have very limited electrical conductivity due to the absence of any low-energy pathway for charge transport. 18-23 This limits the use of MOFs in applications such as fuel cells,24-25 supercapacitors26, electrocatalytic solar fuel generation27-28 and resistive sensing.29 To overcome the inherent insulating properties of MOFs, recent developments on the formation of conductive MOFs19, 30 has utilized a number of different strategies, including: (i) non-continuous band structure, redox-based conductivity through charge hopping between isolated redox-active moieties (linkers, nodes, or postsynthetically appended moieties)31-34 (ii) formation of pi-stacked pathways within the MOF,35-36 (iii) decreasing the energy mismatch of

node-based metal ions and the oxygen- or nitrogenbased linkers by using sulfur-based ligands, that can facilitate charge delocalization,37-39 (iv) introducing guest molecules that bridge the metal nodes to create a through bond charge transport pathway,40 and (v) constructing 2-D structures that exhibit extended piconjugation.41 These ways of making conductive MOFs have shown some success and significantly increased the electrical conductivity, but none have BET surface areas higher than 1,000 m2/g, a number that can be easily exceeded by highly conductive, activated carbon.42 Since the porosity and accessible surface area of a given MOF are often strongly correlated with the material’s performance in applications, retaining both, while imparting electrical conductivity, would be highly desirable, if not essential. Conductive organic polymers, such as polythiophene or polypyrrole, have been investigated for decades.43 Furthermore, MOFs have been used as sacrificial templates to synthesize microporous conductive polymers44-46 and as confined spaces to investigate the inter- and intrachain electronics of polythiophene.47 For these studies, the aim is to fill the MOF micropores—which is necessarily concomitant with elimi-

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nation of porosity and internal surface area. In turn, MOF applications that rely upon both porosity and conductivity have not been feasible with existing polymer/MOF composites. (See, however, the recent report by Le Ouay, et al.48)49 Nevertheless, making use of conductive polymers to impart conductivity is an appealing strategy. We reasoned that by employing a high-area mesoporous MOF and assembling conducting polymers from well-defined and carefully sited building blocks, one could engender tunable electrical conductivity while preserving porosity and surface area. Herein, we propose forming structures comprising narrow strands of conductive polymer. The strands are formed post-synthetically from monodisperse oligomers that are precisely anchored on the inner surface of a wide-channel MOF. Strand formation creates candidate conduction pathways. Because the polymers are selectively sited on the walls of the channels, their formation leaves the bulk of the channel vacant and the overall pore structure and porosity intact (Scheme 1). The wide-channel MOF NU-1000 (31 Å diameter mesopores), a zirconium-based mesoporous MOF, was selected as the platform because it’s hexazirconium(IV)-oxo,hydroxo,aqua nodes render it both chemically robust and amenable to a great variety of post-synthetic modifications.50 By using solvent assisted ligand incorporation (SALI),51 the deprotonated form of p-thio acid, a pentathiophene molecule that has a carboxylate group on the flexible carbon chain can be grafted onto the nodes of NU-1000 in a selflimiting way. In principle, the anchored oligomer can then be subjected to oxidative electropolymerization to yield pore-immobilized polythiophene strands that collectively span the MOF crystallite and that feature the band structure needed to engender electronic conductivity. The self-limiting nature of the p-thio acid installation should ensure that the MOF channels do not overfill with conductive polymer and thereby compromise framework porosity. RESULTS AND DISCUSSION The oligomeric building block p-thio acid was carefully designed to match the interior dimensions and structure of NU-1000. The length of five consecutive thiophenes (17.6 Å) slightly exceeds the distance between nodes (~15 Å, center-to-center) along the MOF c-axis. Thus, the node-anchored oligomers should be capable of contacting each other and polymerizing. At the same time, the flexibility of the aliphatic chain

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should diminish the importance exact distance matching. p-thio acid was synthesized by Sonogashira coupling of 3-bromothiophene with methyl hex-5-ynoate, followed by hydrogenation to yield the center thiophene (Scheme S1). Next the central thiophene was brominated and Stille coupled with 2,2'-bithiophene to yield an ester-functionalized pentathiophene. Ester hydrolysis converted the oligomer to a form useful as a SALI reactant, i.e. p-thio acid. SALI installation of p-thio acid was accomplished by a previously described general procedure.50 NMR measurements of digested samples revealed installation of one p-thio acid per Zr6 node (Figure S11). The polythiophene-functionalized MOF, which we term pentaSALI, was further characterized by powder Xray diffraction (PXRD) and N2 adsorption, The former (Figure 1a) established that crystallinity of NU-1000 is retained; the latter indicates that about 75 % of the gravimetric pore volume and 75 % of the gravimetric BET surface area (S.A.; 1,570 m2g-1 vs. 2,100 m2g-1) are retained, with most of the decrease in each reflecting simply the increase in sample mass (24 %) upon p-thio installation. Notably, the step in the adsorption isotherm near P/P0 = 0.24, which is indicative of sample mesoporosity, is also retained. Consistent with this observation, pore-size-distribution analyses of experimental isotherms show that the diameter of the hexagonal channel in NU-1000 decreases by only a few angstroms upon conversion to pentaSALI. SEM-EDX line scans show that sulfur (and therefore, pentathiophene units) is uniformly distributed through the SALImodified material (Figure S12). Finally, the electronic absorption spectrum shows new features (shoulders at ~380 and ~480 nm) that are attributable to the incorporated oligomer (Figure 1d). To facilitate electropolymerization, suspensions of pentaSALI were spin-cast on conductive glass (fluorine-doped tin oxide (FTO)) to yield electrodesupported thin films of the functionalized MOF; see Supporting Information (SI), Section S5. The supported film was then mounted in a three-electrode electrochemical cell and subjected to cyclic voltammetry. As shown in Figure 2a, consistent with progressive electropolymerization, a gradual increase in current was observed – through about 40 voltammetric cycles.52 In contrast, scanning the unmodified NU-1000 film over the same potential range resulted in no apparent rise in current, consistent with the known absence of redoxactive MOF components over this range.


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Scheme 1. Simplified schematic representation of the synthesis of the proposed conductive polymer/ MOF composite. The scheme is not meant to imply strand alignment solely along the channel direction or to exclude the possibility of strand cross-linking.

Figure 1. a) XRD pattern measured on the thin films of NU-1000, pentaSALI, and Epoly. b) SEM-EDX line scan of the Epoly. The sulfur is evenly distributed throughout the crystal. c) Cross-sectional SEM image of the Epoly film. The thickness is roughly 4 µm. d) UV/Vis. absorption spectrum of the thin films. The absorption was red-shifted after each step.

Returning to the pentaSALI voltammetry, the final lineshape is consistent with the presence of polythiophene, and the existence of a MOF/polymer composite, Epoly, as proposed in Scheme 1. The oxidative current is ascribable to electrochemical doping of the polymer with holes and charge-compensating anions from the electrolyte solution. The excursions to increasingly positive potentials are also accompanied by a change of

film color to dark green—again characteristic of polythiophene doping; see Figure 2b. The electrochromism is reversible (green to brown) and occurs as the polymer is electrochemically de-doped by scanning toward less positive potentials. X-ray diffraction measurements of an Epoly film showed that the crystallinity of NU-1000 is retained (Figure 1a). SEM images show that MOF crystallite



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morphology is unchanged by polythiophene formation (Figure 1b and 1c), while EDS line scans establish polymerization leaves the distribution of sulfur uniform and unchanged (Figure 1b). Consistent with conversion of pentamers to polymers, the electronic absorption spectrum of the composite displays a modest bathochromic shift, (Figure 1d). Electrochemical impedance spectroscopy (EIS; standard three-electrode cell) was used to gauge the electrical conductivity of Epoly, data for Nyquist plots of quadrature (Z”) versus in-phase (Z’) impedance (Figure 3a and 3b) were acquired at various DC potentials (0.5-1.0V vs. Ag/AgCl) based on a small sinusoidal voltage perturbation (10 mV) over a range of the frequencies spanning 300 kHz to 0.03 Hz. Prior to the onset potential at ~ 0.55 V,, the Nyquist plots consist of a single large semi-circle and are essentially the same. This signal is tentatively attributed to the diffusion of the electrolyte (a Warburg component of the impedance) since the polythiophene is in its insulating state and should not contribute to the charge transfer resistance (Rct). As the potential becomes more positive than 0.5 V (and consequently more oxidizing toward the MOF-installed polythiophene), a charge-transfer

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resistance semi-circle starts to appear and the Nyquist plot eventually split into a semi-circle (Rct) and a linear portion (Warburg component), indicating decreased charge-transfer resistance (higher conductivity); see Figure 3, panels a and b. Fits of the EIS data to a simple Randles-type RC circuit yielded Rct values. As outlined in Section S7, potential-dependent conductivities of the thin film were derived from Rct values by considering film dimensions. The results are summarized in Figure 3, panels d. Briefly: a) Conductivity increases with increasing electrochemical doping (panel d). b) Starting from a bias of 0.55 V, where the Rct contribution starts to appear, the measured values of the conductivity of Epoly increase from ~10-9 Scm-1 up to 1.3×10-7 Scm-1 at 1 V (Figure 3d). The latter value is comparable to what has been reported various other electronically conductive MOFs.19 In contrast, over the same DC potentials window, the EIS spectrum of unmodified NU1000 film remains almost unchanged (Figure 3c) due to the lack of a path for electron or hole conduction. (At the most positive potentials, an Rct–like contribution starts to appear, and it may be due to the onset of conductivity via pyrene linker-based redox hopping.53)

Figure 2. a) (black) Cyclic voltammetry during the electropolymerization of pentaSALI to form EPoly. (red) Cyclic voltammetry of NU-1000 in the same potential window. (0.1 M TBAPF6 in CH2Cl2) , Scan rate: 50 mV/s) b) Photos of electrodesupported thin films (left to right): NU-1000, pentaSALI, Epoly (after 40 voltammetric cycles), Epoly (with dedoping; achieved by holding the electrode at 0 V vs. Ag/AgCl for 120 s).


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Figure 3. a) Nyquist plot of the Epoly with applied bias from 0.5V to 1.0 V (frequency range from 300 kHz to 0.03 Hz). b) Zoom-in to the high frequency portion of the Nyquist plot. c) Nyquist plots of the NU-1000 with applied bias from 0.5V to 1.0 V (frequency range from 300 kHz to 0.03 Hz). d) Plot of the log of the conductivity of Epoly versus electrode potential, together with a steady-state cyclic voltammogram of Epoly illustrating electrochemical doping and undoping. The slight displacement of the CV from the log conductivity plot is attributed to a small kinetic lag in doping at the sweep rate employed. Over the range 0.5-0.6 V, the plotted values of the conductivity (marked as hollow squares) may contain significant contributions from a Warburg impedance and therefore may overestimate the true electronic conductivity.

Figure 4. a) (left axis) N2 isotherm recorded at 77 K for NU-1000 and pentaSALI. (right axis) n-Decane isotherm measured at 298 K for NU-1000 and pentaSALI via dynamic vapor sorption (DVS) method. b) QCM trace after dipping into the chamber contains saturated decane. The curves have been staggered for viewing, and the orange bar indicates the time when the QCM crystal was introduced to the decane-saturated atmosphere. The decane uptake (cm3/g) is converted from the measured gravimetric uptake using the density of decane at room temperature (0.73 g/ cm3).



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Due to the small amount of material constituting the Epoly film samples, porosity assessment is not possible via conventional N2 sorption. We turned instead to quartz crystal microgravimetry (QCM)54, a technique with roughly nanogram sensitivity, and used uptake of n-decane (vapor) as a porosity probe. Decane uptake is detected by a shift in the oscillation frequency of a nominally 5 MHz gold-coated quartz crystal (piezoelectric crystal) on which the MOF film resides. Figure 4b shows plots of vapor uptake versus time for exposure of cast films of NU-1000, pentaSALI, and Epoly to saturated atmospheres of decane in air. Since the pore-filling of decane is rapidly happening in the saturated concentration atmosphere, the saturated uptake indicates the accessible pore volume. At saturation, the uptake of n-decane by NU-1000 in thin-film indicates a pore volume of 1.27 cm3g-1, while corresponding dynamic vapor sorption (DVS) measurements of n-decane uptake by bulk NU-1000 reach a very similar number as 1.32 cm3g-1; see Figure 4a. We conclude that the comparatively large alkane is able to access a slightly smaller fraction of the MOF pores than can the small N2 molecule. We also conclude conversion of the MOF from bulk powder to cast-film form preserves all but a few percent of NU-1000’s porosity. Thus the properties of the film appear to be reasonably predictable from the properties of bulk samples, and vice versa. Turning to pentaSALI, and Epoly, these display small but readily measurable decreases in moleculeaccessible pore volume, relative to the porosity of unmodified NU-1000. Versus unmodified, bulk NU1000, pentaSALI displays 73 % of the decane accessible pore volume. (As mentioned, this ratio was 76 % when assessing the pore volume by N2) Versus thinfilm NU-1000, the thin-film pentaSALI and Epoly display respectively, 78 and 75% of the decane-accessible pore volume. Table 1 summarizes the decane porosity results for several samples, relative to the N2-accessible porosity of bulk NU-1000. From the many porosity studies, the most salient findings overall are: a) conversion of the MOF from bulk microcrystalline to thin-film form has only a small effect upon molecule-accessible porosity – an important finding for anticipated applications of MOFs as thin films, b) installation of thiophene pentamers at a density of one pentamer per node translates into loss of only about a quarter of the gravimetric porosity, and c) electrochemical conversion of the channel-anchored oligomers to strands of polythiophene results in little or no additional change in MOF porosity – a similarly significant finding for anticipated applications of conductive MOFs. Table 1. Porosity measurements from the DVS and QCM method.

NU-1000 pentaSALI

Pore volume (N2 @77K)

Pore volume (decane, DVS@ 298K)

Pore volume (decane, QCM@298K)

1.46 cm3g-1

1.32 cm3g-1

1.27 cm3g-1

1.11 cm3g-

0.96 cm3g-1

0.99 cm3g-1

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Epoly

-

-

0. 95cm3g-1 (±4 %)

CONCLUSIONS Electronic conductivity in the mesoporous MOF material, NU-1000, can be engendered by installing thiophene oligomers in limited and controlled fashion within the MOF channels. Carboxylate groups serve to anchor the oligomers to the MOF walls, leaving the channels largely open. For example, the diameter of the mesoporous channel in NU-1000 only marginally decreases, i.e. from 31 Å to 27 Å. The overall porosity, as gauged by measurements of molecule-accessible gravimetric pore volume and (N2 or n-decane) decreases by only about 25%, while the BET gravimetric surface area also decreases by similar amout. (a significant portion of which is attributable to the increase in sample mass with oligomer installation). With the appropriate choice of thiophene oligomer, the length of the oligomer closely matches the oligomer-center to oligomer-center separation distance – a circumstance that is ideal for oxidative linking of thiophene pentamers to form channel-anchored strands of polythiophene. Indeed, by making use of the functionalized MOF, pentaSALI, in electrode-supported, thinfilm form, the desired conversion of oligomer to polymer can be both initiated and followed electrochemically. The resulting composite displays potentialdependent (doping-dependent) electronic conductivity that reaches its maximum at the most positive electrode potential examined, +1.0 V vs. Ag/AgCl. Most importantly, the conductivity is attained without substantial sacrifice of porosity and surface area, a problem that until now has been difficult to circumvent. Indeed, the BET surface area of pentaSALI and, by inference, Epoly is 1,560 m2g-1, i.e. significantly greater than observed for the vast majority of MOF materials and on par with many porous (conductive) carbon materials. We suggest that the approach demonstrated here for engendering MOF electronic conductivity should be applicable to related mesoporous MOFs. The availability of MOF electronic conductivity should open up (or expand) opportunities for application of MOFs as chemo-resistive sensors, high-density electrocatalysts, and pseudo-capacitance based energy storage compounds.36

EXPERIMENTAL SECTION Materials and Methods NU-1000 was synthesized according to a method reported in the literature.50 3-bromothiophene (SigmaAldrich), methyl hex-5-ynoate (GFS Chemicals), CuI (Sigma-Aldrich), PdCl2(PPh3)2 (Strem), Pd/C (Strem), NBS (Sigma-Aldrich), 2,2'-bithiophene (SigmaAldrich), tetrabutylammonium hexafluorophosphate (TCI) was purchased from vendors and used without purification. All solvents and reagents not specified above are purchased from Sigma-Aldrich, and all deuterated solvents were from Cambridge Isotopes Laboratory. Deionized water was used throughout the work.


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All air sensitive reactions were performed using standard Schlenk line technique. Instrumentation Activation of MOF samples was performed on a Micromeritics SmartVacPrep and N2 adsorption isotherms were measured on a Micromeritics Tristar II 3020 at 77 K with the temperature held constant using liquid N2 bath. Thin film X-ray diffraction (PXRD) patterns were recorded on a Rigaku ATXG diffractometer equipped with an 18 kW Cu rotating anode, MLO monochromator, and a high-count-rate scintillation detector. Scanning electron microscopy (SEM) images and energy-dispersive X-ray spectroscopy (EDX) mapping were recorded on a Hitachi SU8030 SEM. NMR were measured on a Bruker Avance III 500 MHz system, equipped with DCH CryoProbe. All cyclic voltammetric (CV) experiments were performed on a CHI 660 electrochemical workstation (CH Instruments, Inc., USA). A three-electrode electrochemical setup was used, with a platinum mesh and Ag/AgCl/KCl (sat'd) electrode as the counter electrode and reference electrode, respectively. Electrochemical impedance spectroscopy (EIS) experiments were conducted on a ModuLab ECS potentiostat (Solartron Analytical) with the same threeelectrode setup to measure the current densitypotential (J-V) curves. UV/vis. absorption spectrum were measured on a Cary 5000 spectrophotometer (Varian). Dynamic vapor sorption (DVS) was measured on a Hiden Isochema Intelligent Gravimetric Analyzer (IGA-200) equipped with water bath at 298 K. All isotherms were recorded using IGASwin software (v1.06) that utilizes a linear driving force model and corrects all data point for the buoyancy effects; thus the adsorbed mass at a given relative pressure point was the difference of mass gain at that point relative to the mass recorded in dry N2 flow. Dry N2 was used as carrier gas and was mixed with decane vapor saturated N2 gas stream, generated by bubbling N2 gas through a decane reservoir at 298 K, at the required concentration or relative pressure; the total flow rate was 100 cc/min. QCM porosity measurements were conducted on a Research Quartz Crystal Microbalance (RQCM, Maxtekinc. Inc., CA) equipped with a 5 KΩ QCM polished gold electrode sensors (Maxtekinc. Inc., CA) that are fitted into a propylene QCM holder. QCM crystals were cleaned with acetone or methanol and dried over N2 flow. They were then placed into an 80 °C preheated oven prior for at least 1 hour and allowed to cool down to room temperature at which point the initial resonant frequencies were measured before sample was spin coated. Synthesis procedure for incorporating p-thio acid into NU-1000 (pentaSALI) NU-1000 (50 mg, 0.023 mmol) and p-thio acid (30 mg, 0.057 mmol) was added into a 6-dram vial, and DMF (4 mL) was added. The vial was sonicated briefly to dissolve the p-thio acid, and then the vial was incubated in a 60 °C oven for 1 d. The solid sample was collected by centrifugation. The solid was washed and soaked with fresh DMF for 3 times over a day, and then solvent was exchanged to acetone (3 times soaking over a day). The solid was dried under dynamic vacuum at 60 °C for 12 h, and subjected to N2 sorption measure-

ment. The sample needs to be stored in inert atmosphere if not immediately used. Preparation of thin films for electrochemical measurement pentaSALI (10 mg) or NU-1000 (10 mg) was suspended in 1.5 mL of acetone with the aid of sonication. FTO glass (1.25 cm × 2.5 cm) was placed on a spin coater and spun at 1500 rpm. 15 drops of the prepared suspension was slowly dropped onto the spinning FTO glass, and the spin rate was accelerated to 5000 rpm for additional 30 s. The freshly-casted samples need to be stored in inert atmosphere if not immediately used. The average thickness from this procedure is ~ 4 µm by cross-section SEM images.

ASSOCIATED CONTENT Supporting Information Detail information for synthesis of p-thio acid, additional characterization, and the calculation of the conductivity. This material is available free of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION Corresponding Authors [email protected]; [email protected]

ACKNOWLEDGMENTS We thank Dr. Chung-Wei Kung for helpful discussions. We gratefully acknowledge financial support from the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences (grant No. DE-FG02 87ER13808) and Northwestern University. C.O.A. thanks the U.S. National Science Foundation for an NSF Predoctoral Graduate Fellowship.

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30. Stavila, V.; Talin, A. A.; Allendorf, M. D., MOF-Based Electronic and Opto-Electronic Devices. Chem. Soc. Rev. 2014, 43 (16), 5994-6010. 31. Hod, I.; Bury, W.; Gardner, D. M.; Deria, P.; Roznyatovskiy, V.; Wasielewski, M. R.; Farha, O. K.; Hupp, J. T., Bias-Switchable Permselectivity and Redox Catalytic Activity of a Ferrocene-Functionalized, Thin-Film Metal–Organic Framework Compound. J. Phys. Chem. Lett. 2015, 6 (4), 586-591. 32. D'Alessandro, D. M., Exploiting Redox Activity in Metal-Organic Frameworks: Concepts, Trends and Perspectives. Chem. Commun. 2016, 52 (58), 8957-8971. 33. Maza, W. A.; Haring, A. J.; Ahrenholtz, S. R.; Epley, C. C.; Lin, S. Y.; Morris, A. J., Ruthenium(ii)-Polypyridyl Zirconium(iv) Metal-Organic Frameworks as a New Class of Sensitized Solar Cells. Chem. Sci. 2016, 7 (1), 719-727. 34. Fei, H.; Pullen, S.; Wagner, A.; Ott, S.; Cohen, S. M., Functionalization of Robust Zr(iv)-Based Metal-Organic Framework Films via a Postsynthetic Ligand Exchange. Chem. Commun. 2015, 51 (1), 66-69. 35. Narayan, T. C.; Miyakai, T.; Seki, S.; Dincă, M., High Charge Mobility in a Tetrathiafulvalene-Based Microporous Metal–Organic Framework. J. Am. Chem. Soc. 2012, 134 (31), 12932-12935. 36. Leong, C. F.; Chan, B.; Faust, T. B.; D'Alessandro, D. M., Controlling Charge Separation in a Novel Donor-Acceptor Metal-Organic Framework via Redox Modulation. Chem. Sci. 2014, 5 (12), 4724-4728. 37. Sun, L.; Miyakai, T.; Seki, S.; Dincă, M., Mn2(2,5disulfhydrylbenzene-1,4-dicarboxylate): A Microporous Metal– Organic Framework with Infinite (−Mn–S−)∞ Chains and High Intrinsic Charge Mobility. J. Am. Chem. Soc. 2013, 135 (22), 8185-8188. 38. Kobayashi, Y.; Jacobs, B.; Allendorf, M. D.; Long, J. R., Conductivity, Doping, and Redox Chemistry of a Microporous Dithiolene-Based Metal−Organic Framework. Chem. Mater. 2010, 22 (14), 4120-4122. 39. Takaishi, S.; Hosoda, M.; Kajiwara, T.; Miyasaka, H.; Yamashita, M.; Nakanishi, Y.; Kitagawa, Y.; Yamaguchi, K.; Kobayashi, A.; Kitagawa, H., Electroconductive Porous Coordination Polymer Cu[Cu(pdt)2] Composed of Donor and Acceptor Building Units. Inorg. Chem. 2009, 48 (19), 90489050. 40. Talin, A. A.; Centrone, A.; Ford, A. C.; Foster, M. E.; Stavila, V.; Haney, P.; Kinney, R. A.; Szalai, V.; El Gabaly, F.; Yoon, H. P.; Léonard, F.; Allendorf, M. D., Tunable Electrical Conductivity in Metal-Organic Framework Thin-Film Devices. Science 2014, 343 (6166), 66-69. 41. Sheberla, D.; Sun, L.; Blood-Forsythe, M. A.; Er, S.; Wade, C. R.; Brozek, C. K.; Aspuru-Guzik, A.; Dincă, M., High Electrical Conductivity in Ni3(2,3,6,7,10,11hexaiminotriphenylene)2, a Semiconducting Metal–Organic Graphene Analogue. J. Am. Chem. Soc. 2014, 136 (25), 88598862. 42. Hu, Z.; Srinivasan, M. P.; Ni, Y., Preparation of Mesoporous High-Surface-Area Activated Carbon. Adv. Mater. 2000, 12 (1), 62-65. 43. Nalwa, H. S., Conductive Polymers: Transport, Photophysics and Applications. Wiley: London, 1997. 44. Lu, C.; Ben, T.; Xu, S.; Qiu, S., Electrochemical Synthesis of a Microporous Conductive Polymer Based on a Metal–Organic Framework Thin Film. Angew. Chem., Int. Ed. 2014, 53 (25), 6454-6458. 45. Wang, L.; Feng, X.; Ren, L.; Piao, Q.; Zhong, J.; Wang, Y.; Li, H.; Chen, Y.; Wang, B., Flexible Solid-State Supercapacitor Based on a Metal–Organic Framework Interwoven by Electrochemically-Deposited PANI. J. Am. Chem. Soc. 2015, 137 (15), 4920-4923. 46. Mulzer, C. R.; Shen, L.; Bisbey, R. P.; McKone, J. R.; Zhang, N.; Abruña, H. D.; Dichtel, W. R., Superior Charge Storage and Power Density of a Conducting Polymer-Modified Covalent Organic Framework. ACS Cent. Sci. 2016, 2 (9), 667-673. 47. MacLean, M. W. A.; Kitao, T.; Suga, T.; Mizuno, M.; Seki, S.; Uemura, T.; Kitagawa, S., Unraveling Inter- and Intrachain Electronics in Polythiophene Assemblies Mediated by Coordination Nanospaces. Angew. Chem., Int. Ed. 2016, 55 (2), 708-713.


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48. Le Ouay, B.; Boudot, M.; Kitao, T.; Yanagida, T.; Kitagawa, S.; Uemura, T., Nanostructuration of PEDOT in Porous Coordination Polymers for Tunable Porosity and Conductivity. J. Am. Chem. Soc. 2016, 138 (32), 10088-10091. 49. While this manuscript was being prepared, an example of using controlled loading of conductive polymer in MOF to enhance electrical conductivity is reported by Kitagawa et. al (ref. 48). Our composite has achieved comparable conductivity as the aforementioned work, if one would look into the measured conductivity for the polythiophene composite in the supplementary information instead of the PEDOT composite that is reported in the main text. However, due to our improved way of introducing the monomer in the parent MOF, we could achieved more even distribution of the monomer, thus forming longer continuous polymer chain with less incorporation of thiophene monomers. 50. Wang, T. C.; Vermeulen, N. A.; Kim, I. S.; Martinson, A. B. F.; Stoddart, J. F.; Hupp, J. T.; Farha, O. K., Scalable Synthesis and Post-Modification of a Mesoporous Metal-Organic Framework Called NU-1000. Nat. Protocols 2016, 11 (1), 149162. 51. Deria, P.; Mondloch, J. E.; Tylianakis, E.; Ghosh, P.; Bury, W.; Snurr, R. Q.; Hupp, J. T.; Farha, O. K., Perfluoroalkane Functionalization of NU-1000 via Solvent-Assisted Ligand

Incorporation: Synthesis and CO2 Adsorption Studies. J. Am. Chem. Soc. 2013, 135 (45), 16801-16804. 52. Based on comparisons of the magnitude of charge passed in cyclic voltammetric measurements of films of EPoly (Figure 2a) versus NU-1000 (Figure S13), we conclude that the majority of MOF-installed pentathiophene units, including units in the MOF interior, are electropolymerized. For NU-1000, the observed current is due to reversible oxidation of the MOF linkers. We have previously observed that, within experimental error, all of the pyrene linkers in films of NU-1000 are electrochemically addressable (ref 53). 53. 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., Directed Growth of Electroactive MetalOrganic Framework Thin Films Using Electrophoretic Deposition. Adv. Mater. 2014, 26 (36), 6295-6300. 54. Wannapaiboon, S.; Tu, M.; Sumida, K.; Khaletskaya, K.; Furukawa, S.; Kitagawa, S.; Fischer, R. A., Hierarchical Structuring of Metal-Organic Framework Thin-Films on Quartz Crystal Microbalance (QCM) Substrates for Selective Adsorption Applications. J. Mater. Chem. A 2015, 3 (46), 23385-23394.



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