SUPPLEMENTARY INFORMATION

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1 Supplementary information for Gas detection by structural variations of fluorescent guest molecules in flexible coordination nanopores Nobuhiro Yanai, Koji Kitayama, Yuh Hijikata, Hiroshi Sato, Ryotaro Matsuda, Yoshiki Kubota, Masaki Takata, Motohiro Mizuno, Takashi Uemura*, and Susumu Kitagawa* * To whom corresponding should be addressed. uemura@sbchem.kyoto-u.ac.jp; kitagawa@icems.kyoto-u.ac.jp NATURE MATERIALS 1

2 Measurements. X-ray powder diffraction (XRPD) data were collected on a Rigaku RINT 2000 Ultima diffractometer with Cu Kα radiation. Scanning electron microscope (SEM) measurement was performed by use of a Hitachi S-3000N at an accelerating voltage of 5 kv. Samples were put on a conducting carbon tape attached by SEM grid, and then coated with platinum. Elemental analysis was performed on a Flash EA 1112 series (Thermo Finnigan instrument). The sorption isotherms of N 2, Ar, and CO 2 were measured with a Quantachrome Autosorb-1 volumetric adsorption instrument. N 2, Ar, and CO 2 gas of high purity ( %) was used. The sorption isotherm for MeCN was recorded on a BELSORP18-Plus volumetric adsorption instrument. Prior to the adsorption measurements, the sample was treated under reduced pressure (<10-2 Pa) at 373 K for 5 h. Differential scanning calorimetry (DSC) was carried out with Seiko Instruments DSC 6220 under N 2 atmosphere. The Raman measurements were carried at room temperature with the Raman spectrometer HORIBA Jobin Yvon LabRam HR800. The excitation light source was a semiconductor laser of nm wavelength. Thermogravimetric analysis (TGA) was performed at 10 K/min with a Rigaku Instrument Thermo plus TG 8120 in a nitrogen atmosphere. Solid-state CPMAS 13 C NMR was measured by JEOL JNM-LA300WB spectrometer operated at 75.6 MHz. Solid-state 2 H NMR spectra were measured by a Varian Chemagnetics CMX-300 spectrometer at 45.8 MHz with a quadrupole echo pulse sequence. Simulated spectra were produced with FORTRAN programs written by us. For infrared (IR) spectroscopy, thin wafers of the samples were prepared and degassed at 373 K for 1 h in vacuo and cooled to the measurement temperature (298 K for acetonitrile and 195 K for CO 2 ) inside an Oxford cryostat MicrostatN, which allowed in situ sample activation, gas dosage and temperature control. IR spectra were recorded on a JASCO model FT/IR-4200 Fourier transform infrared spectrometer. Fluorescence spectra were measured on Fluorolog-3 (HORIBA Jobin Yvon Inc.) with double-grating monochromators, 450-W xenon lamp, and R928 photomultiplier tube run in photon-counting mode. Fluorescence quantum yield was measured on a Fluorolog-3 with an integrating sphere. Fluorescence lifetimes were obtained by the time-correlated single-photon-counting method, using FluoroCube (HORIBA Jobin Yvon IBH) equipped with a nanosecond pulsed LED (λex = 333 nm). The monitor emission wavelength was set at 460 nm in each compound. Fluorescence lifetimes were fit with DAS6 (decay analysis software from HORIBA Jobin Yvon IBH). Synchrotron X-ray powder diffraction measurements and analysis. The powder samples were sealed in a silica glass capillary. XRPD patterns with good counting statistics were measured by the in situ synchrotron radiation XRPD experiment with the large Debye-Scherrer camera and imaging plate as detectors on the BL02B2 beam line at SPring-8. Indexing was carried out by the program DICVOL06. The crystal systems of the samples were found to be orthorhombic. Unit cell refinements were obtained by using the Le Bail fitting method. 2 NATURE MATERIALS

3 SUPPLEMENTARY INFORMATION Density functional calculations. Density functional calculations were performed with B3LYP/6-311+G** basis set. All calculations were carried out with Gaussian 03 revision E.01. The wavenumbers of the normal vibrations calculated by density functional theory (DFT) were multiplied by a scaling factor of Vibrational wavenumbers were calculated for the DSB molecule by varing the torsional angles θ, τ 1 and τ 2. The angle θ is defined as the torsional angle around the C=C bonds in the H-C=C-H linkage in the way similar to the definition in the literature. 1 The angles τ 1 and τ 2 are defined around the outer and inner C-phenyl bonds, respectively, in the C=C-C-C linkage. 1 Optimization of structural parameters was carried out with the structural symmetry of C i and prefixed value of the θ. IR spectra were obtained based on the optimized structures. NATURE MATERIALS 3

4 Figure S1. XRPD patterns for (a) 1, (b) 1ʹ DSB, (c) 1 [DSB + MeCN], (d) 1 DSB, and (e) the solid obtained after heating 1 DSB at 423 K. The host framework 1 shrunk to form the rhombic net structure 1ʹ by the incorporation of DSB. By exposing 1ʹ DSB to MeCN vapour, the host structure was changed from the deformed 1ʹ to the original 1, which generated the co-adsorption state, 1 [DSB + MeCN]. After the removal of MeCN from 1 [DSB + MeCN] by vacuuming at 273 K, the host structure remained undeformed, which provided the composite 1 DSB. The heating treatment upon 1 DSB induced the host structural change from the original 1 to the deformed 1ʹ. 4 NATURE MATERIALS

5 SUPPLEMENTARY INFORMATION Figure S2. SEM images of (a) 1, (b) 1ʹ DSB, (c) 1 DSB, and (d) bulk DSB. Scale bars = 5 µm. The crystal size and morphology of the host did not change during the loading process of DSB and the adsorption/desorption of MeCN. Contamination of bulk DSB crystals in the composites was undetected in the SEM pictures. NATURE MATERIALS 5

6 Figure S3. The results of the Le Bail fitting analysis for the synchrotron XRPD patterns of (a) 1ʹ DSB under vacuum and of (b) 1ʹ DSB at P/P 0 = 0.05 of MeCN vapour at 298 K. 6 NATURE MATERIALS

7 SUPPLEMENTARY INFORMATION Figure S4. IR spectra for 1, bulk DSB, and 1ʹ DSB. The IR spectrum of bulk DSB has a few peaks around 970 cm -1 that are assignable to a CH out-of-plane bending vibration of the CH=CH groups. 1 When DSB was incorporated into the nanochannels, these peaks clearly shifted to 954 cm -1. NATURE MATERIALS 7

8 Figure S5. a, Torsional angles θ, τ 1 and τ 2 for each optimized structures. b, Torsional angles dependency of the calculated IR spectrum for DSB. The IR band of the CH out-of-plane bending vibration shifts to lower wavenumbers with increasing the torsional angles. This result suggests that the DSB molecules in the bulk crystals are almost planar, in contrast, those in the rhombic channels of 1ʹ are twisted. 8 NATURE MATERIALS

9 SUPPLEMENTARY INFORMATION Figure S6. Raman spectra for 1, bulk DSB, 1 DSB, 1 [DSB + MeCN], and 1ʹ DSB. There are no bands with strong intensity in the region of the CH out-of-plane vibration of the CH=CH groups in the Raman spectra of bulk DSB, 1 [DSB + MeCN] and 1 DSB. In contrast, 1ʹ DSB clearly showed a Raman band at 954 cm -1. It has been reported that the CH out-of-plane vibration of a CH=CH group with a planar structure is Raman-inactive, but that with a twisted conformation turns into a Raman-active mode. 1 The DSB molecules embedded within bulk DSB, 1 [DSB + MeCN] and 1 DSB are almost planar, and those in the rhombic channels of 1ʹ are twisted. These findings are well consistent with the IR results. NATURE MATERIALS 9

10 Figure S7. Absorption spectra for the DSB solution (black) and 1ʹ DSB (red). The absorption band of the composite 1ʹ DSB significantly redshifted against DSB in solution. This shift is the consequence of the formation of J-aggregates of the DSB molecules in the nanochannels NATURE MATERIALS

11 SUPPLEMENTARY INFORMATION Figure S8. Excitation spectra (fluorescence at 460 nm) for 1ʹ DSB (black) and 1ʹ [DSB + CO 2 ] (P = 100 kpa) (blue). Although the conformational planarization usually extends the effective π-conjugation length of the molecules, the excitation spectra showed a slight blue shift after the CO 2 uptake. 5 This blue shift is probably because of the alteration of the aggregation structure of DSB. 3,4 NATURE MATERIALS 11

12 Figure S9. Fluorescence spectra (excitation at 340 nm) for 1ʹ DSB under vacuum (black), CO 2 (blue, P = 80 kpa), N 2 (red, P = 100 kpa), O 2 (purple, P = 100 kpa), and Ar (green, P = 100 kpa) at 195 K. The clear change of fluorescence was observed only under CO 2 atmosphere, which demonstrates the selective detection of CO 2 over other atmospheric gases. 12 NATURE MATERIALS

13 SUPPLEMENTARY INFORMATION Figure S10. Fluorescence spectra (excitation at 340 nm) for the composites of DSB with (a) LaBTB (MIL-103, BTB = 1,3,5-benzenetribenzoate) 6 and (b) Zr 6 O 4 (OH) 4 (BPDC) 12 (UiO-67, BPDC = 4,4 -biphenyldicarboxylate) 7 under vacuuum (black) and CO 2 (blue, P = 100 kpa). The DSB molecules were introduced into these rigid host frameworks by the sublimation method similar to the preparation of 1ʹ DSB. TGA data showed that the incorporation amount of DSB in MIL-103 and UiO-67 (weight of DSB/weight of host) are 0.16 and 0.21, respectively, where the DSB molecules occupy less than 60% of the total void volumes of these hosts. The DSB molecules form the planar conformation in these composites under vacuum as evidenced by IR bands at 967 cm -1 and 963 cm -1 for DSB in MIL-103 and UiO-67, respectively. These positions of the IR bands was not changed under CO 2 (P = 100 kpa). The structured fluorescence spectra were observed for these composites under vacuum because of the planar conformation of DSB. The fluorescence of DSB in these composite materials was not sensitive to CO 2, which highlights the importance of framework transformation for the fluorescence response to CO 2. NATURE MATERIALS 13

14 Figure S11. Adsorption isotherm of water for 1ʹ DSB at 298 K. It is necessary, from a practical standpoint, to take into account the effect of water vapour. The composite material did not show significant water uptake below P/P 0 = 0.68, probably due to the hydrophobic nature of the host framework and DSB molecules. This indicates that water would not interfere with the gas detection unless the humidity is very high (above 70%). 14 NATURE MATERIALS

15 SUPPLEMENTARY INFORMATION Figure S12. In situ fluorescence spectra (excitation at 340 nm) with increasing vapour pressure of water for 1ʹ DSB. No change in the fluorescence spectra was observed below P/P 0 = The further increase of vapour pressure to P/P 0 = 0.84 did not result in a large change in the fluorescence spectra. In addition, this fluorescence change took about 20 minutes, which is considerably slower than the response to gas molecules. Thus, the detection performance using 1ʹ DSB would not be influenced by water. NATURE MATERIALS 15

16 Figure S13. Schematic illustration for the reversible structural changes of the composite by co-adsorption of MeCN and heat treatment. The adsorption of MeCN on 1ʹ DSB induces host structural transformation and guest conformational changes, providing the co-adsorption state, 1 [DSB + MeCN]. The host structure and guest conformations are maintained after the removal of MeCN from 1 [DSB + MeCN]. The obtained composite 1 DSB is converted to 1ʹ DSB by the heat treatment. It is interesting that the composite material has a unique memory effect after the removal of MeCN. This memory effect was not observed after the removal of CO 2 from 1 [DSB + CO 2 ]. The origin of these different behaviours might be explained by the different DSB conformations in 1 [DSB + MeCN] and 1 [DSB + CO 2 ]. The IR measurements showed that the twisted conformation of DSB in 1ʹ DSB was not fully changed to the planar form during the CO 2 adsorption (Fig. 3c), and thus the subsequent removal of CO 2 might regenerated the twisted DSB conformation. However, MeCN uptake by 1ʹ DSB resulted in the complete conversion of the twisted conformation to the planar conformation (Fig. S19). The conformational twisting of this planar DSB molecule might require a certain activation energy. 8 In fact, the heat treatment of 1 DSB overcame the activation energy and produced the original composite 1ʹ DSB (Fig. S1). Furthermore, 1 DSB slowly relaxed to 1ʹ DSB at room temperature over several months (Fig. S24). 16 NATURE MATERIALS

17 SUPPLEMENTARY INFORMATION Figure S14. XRPD patterns for (a) 1ʹ DSB, the solid obtained after exposing 1ʹ DSB to vapours of (b) MeCN, (c) MeOH, (d) acetone, (e) CH 2 Cl 2, and (f) toluene, and (g) bulk DSB. By being exposed to the solvent vapours, the deformed host framework 1ʹ adsorbed the solvent molecules and was converted to the original form 1. When polar solvents such as MeCN, MeOH, and acetone were employed as the second guests, the peaks for bulk DSB were not observed in the XRPD patterns. However, when non-polar solvents such as CH 2 Cl 2 and toluene were used, the resulting XRPD patterns contained the peaks of the bulk DSB crystals at around 5 and 15. The polar molecules and DSB coexisted in nanochannels of 1, but DSB was replaced by the non-polar molecules. Therefore, we employed polar molecules as the second guests. NATURE MATERIALS 17

18 Figure S15. Fluorescence spectra (excitation at 340 nm) for the solid obtained after exposing 1ʹ DSB to vapours of MeCN (black), MeOH (red), and acetone (blue). 18 NATURE MATERIALS

19 SUPPLEMENTARY INFORMATION Figure S16. Adsorption isotherm of MeCN for 1ʹ DSB at 298 K. NATURE MATERIALS 19

20 Figure S17. In situ fluorescence spectra (excitation at 340 nm) with increasing vapour pressure of MeCN for 1ʹ DSB. The inset shows the vapour pressure dependence of fluorescence intensity at 440 nm of the composite. 20 NATURE MATERIALS

21 SUPPLEMENTARY INFORMATION Figure S18. Synchrotron XRPD patterns for for 1ʹ DSB at various pressures of MeCN. Schematic representation of the stepwise breathing phenomenon of the host framework is also shown. The first uptake of MeCN is associated with the structural transition to an intermediate form, as evident from the XRPD pattern obtained at P/P 0 = Further structural change was detected during the second step of adsorption, and the XRPD pattern at P/P 0 = 0.80 closely approximates that of the original host 1. The cell parameters of the intermediate phase could be determined by the Le Bail fitting analysis, which features the angle of 84 between sides of the 2-D net (Fig. S3, Table S1). Thus, the rhombic network structure of 1ʹ DSB returned to the original square form in the stepwise fashion during the MeCN sorption. After the adsorption of MeCN, the DSB molecules remained in the nanochannels of 1 (Fig. S14). NATURE MATERIALS 21

22 Figure S19. IR spectra for 1ʹ DSB under various pressures of MeCN and 1 DSB. The IR bands of CH out-of-plane bending vibration of the CH=CH groups gradually changed in the pressure region corresponding to the steps of the adsorption isotherm. The IR bands of 1 DSB were similar to those for 1 [DSB + MeCN], indicating that the DSB molecules still have the planar conformation after the removal of MeCN. 22 NATURE MATERIALS

23 SUPPLEMENTARY INFORMATION Figure S20. TGA profiles of 1ʹ DSB (black), 1 [DSB + MeCN] (red), 1 DSB (blue), and bulk DSB (green). The heating rate of the measurements was 10 K min -1. The observed weight loss of 17.6 % up to 423 K for 1 [DSB + MeCN] corresponds to release of MeCN from the composite, which is in good agreement with the saturated value of the adsorption isotherm of MeCN on 1ʹ DSB. No weight loss up to 423 K was observed for 1 DSB, which indicates that the vacuuming at 273 K of 1 [DSB + MeCN] resulted in the complete removal of MeCN from the composite. Sublimation of bulk DSB commences at 420 K, in contrast, the release of DSB and the decomposition of the host framework simultaneously occurred above 550 K. These observations point to the accommodation and stabilization of DSB in the nanochannels within the composites. NATURE MATERIALS 23

24 Figure S21. Solid-state CPMAS 13 C NMR spectra for 1ʹ DSB, 1 [DSB + MeCN], and 1 DSB. Asterisks mark spinning side bands. The peaks for MeCN were observed in the spectrum of 1 [DSB + MeCN], but these were absent in the spectrum of 1 DSB. We can conclude that the MeCN molecules were completely removed in 1 DSB. 24 NATURE MATERIALS

25 SUPPLEMENTARY INFORMATION Figure S22. Fluorescence spectra (excitation at 340 nm) for 1ʹ DSB (black), 1 [DSB + MeCN] (blue), 1 DSB (purple), and the solid obtained after heating 1 DSB at 423 K (red). The broad spectrum for 1ʹ DSB was changed to the structured one by the adsorption of MeCN. The subsequent removal of MeCN from 1 [DSB + MeCN] did not affect the fluorescence spectrum. After the heating treatment upon 1 DSB, the obtained solid showed the broad spectrum similar to that of 1ʹ DSB. Therefore, the DSB fluorescence was reversibly converted responding to the different host structures, which confirms the scenario that cooperative host-guest transformations play a key role in the fluorescence changes. NATURE MATERIALS 25

26 Figure S23. DSC heating curves of 1 DSB. The heating rate of the measurements was 10 K min NATURE MATERIALS

27 SUPPLEMENTARY INFORMATION Figure S24. XRPD patterns for (a) 1 DSB, the solid obtained after keeping 1 DSB at room temperature for (b) 1 month, (c) 4 month, and (d) 11 month, and (e) 1ʹ DSB. The peaks for 1ʹ DSB were not observed in 1 DSB, indicating 1 DSB is scarcely contaminated by 1ʹ DSB. After leaving 1 DSB at room temperature for several months, the host structure was gradually transformed to that of 1ʹ DSB. The kinetically stable phase 1 DSB was gradually relaxed into the thermodynamically stable phase 1ʹ DSB at room temperature. NATURE MATERIALS 27

28 Figure S25. Solid state 2 H NMR spectra of (a) 1ʹ DSB-d 12, (b) 1 DSB-d 12, and (c) bulk DSB-d 12. The simulation results are shown as red lines. Deuterated DSB-d 12 was incorporated into the channels of 1 to investigate the mobility of DSB by using solid-state 2 H NMR. We successfully carried out the spectral simulation for 1ʹ DSB-d 12 in the presence of 180 flip of the phenyl rings with rotation rates of s -1. The spectrum of bulk DSB-d 12 showed typical rigid limit line shape, indicating that the motional processes are slow and outside the sensitive range of the 2 H NMR experiments. The spectrum for 1 DSB-d 12 was significantly different from those for 1ʹ DSB-d 12 and bulk DSB-d 12. The spectral width for 1 DSB-d 12 was narrower than those for 1ʹ DSB-d 12 and bulk DSB-d 12. We succeeded in obtaining theoretical patterns for 1 DSB-d 12 on the basis of the free rotation model of the benzene rings, and clearly observed that the rotation frequency of DSB-d 12 in 1 is greater than those in 1ʹ and within bulk crystals. In addition, these results suggest that the DSB molecules of 1 DSB-d 12 are located in the nanochannels of 1 and do not form the bulk crystal outside the pores. 28 NATURE MATERIALS

29 SUPPLEMENTARY INFORMATION Table S1. The results of the Le Bail fitting analysis for the synchrotron XRPD patterns of 1ʹ DSB under vacuum and of 1ʹ DSB at P/P 0 = 0.05 of MeCN vapour at 298 K. The angles between sides of the 2-D net are 75 and 84 for 1ʹ DSB under vacuum and MeCN vapour, respectively. The volumes per dinuclear Zn 2 unit are 1078 Å 3 and 1128 Å 3 for 1ʹ DSB under vacuum and MeCN vapour, respectively. The cell parameters of 1ʹ DSB is close to those of the compound obtained by introducing benzene into 1. 9 The crystal structure of the benzene-included material is shown below the table. compound 1ʹ DSB 1ʹ DSB at P/P 0 = 0.05 of MeCN vapour a / Å (1) (3) b / Å (1) (2) c / Å (1) 9.623(1) α, β, γ / V / Å (6) (6) R wp NATURE MATERIALS 29

30 Table S2. Physical parameters and thermodynamic properties of CO 2 and C 2 H NATURE MATERIALS

31 SUPPLEMENTARY INFORMATION Supplementary References 1. Furuya, K., Kawato, K., Yokoyama, H., Sakamoto, A. & Tasumi, M. Molecular distortion of trans-stilbene and the Raman intensity of the in-phase CH out-of-plane wag of the central CH=CH group. J. Phys. Chem. A 107, (2003). 2. An, B.-K., Kwon, S.-K., Jung, S.-D. & Park, S. Y. Enhanced emission and its switching in fluorescent organic nanoparticles. J. Am. Chem. Soc. 124, (2002). 3. Oelkrug, D. et al. Towards highly luminescent phenylene vinylene films. Synth. Met. 83, (1996). 4. Kasha, M., Rawls, H. R. & El-Bayoumi, M. A. The exciton model in molecular spectroscopy. Pure Appl. Chem. 11, (1965). 5. Oelkrug, D. et al. Tuning of fluorescence in films and nanoparticles of oligophenylenevinylenes. J. Phys. Chem. B 102, (1998). 6. Devic, T., Serre, C., Audebrand, N., Marrot, J. & Férey, G. MIL-103, a 3-D lanthanide-based metal organic framework with large one-dimensional tunnels and a high surface area. J. Am. Chem. Soc. 127, (2005). 7. Cavka, J. H. et al. A new zirconium inorganic building brick forming metal organic frameworks with exceptional stability. J. Am. Chem. Soc. 130, (2008). 8. Tuncel, D., Ozsar, O., Tiftik, H. B. & Salih, B. Molecular switch based on a cucurbit[6]uril containing bistable [3]rotaxane. Chem. Commun (2007). 9. Dybtsev, D. N., Chun, H. & Kim, K. Rigid and flexible: A highly porous metal-organic framework with unusual guest-dependent dynamic behavior. Angew. Chem. Int. Ed. 43, (2004). NATURE MATERIALS 31