English

• INTRODUCTION

  Metal-organic frameworks (MOFs) materials^[1-4] constructed from metal ions (clusters) and organic ligands have been widely concerned, because of their diverse structures and fascinating potential of applications in broad fields of catalysis, ^{[5, 6]}adsorption/separation, ^[7-9] optical, ^{[10, 11]} energy storage^{[12, 13]} and so on. As a subclass of MOFs materials, chiral MOFs (chirMOFs)^{[14, 15]} have attracted great attention on the potential applications in asymmetric catalysis, ^{[16, 17]} enantioselective adsorption/separation^[18], nonlinear optics, ^{[19, 20]} and drug delivery^[21]. In order to meet the requirement of practical applications in many fields, recently chiral MOFs with the form of thin films or membranes have been realized to be advanced candidates for chiral recognition, ^{[22, 23]} enantiomers separation, ^[24] and photoelectronic applications.^{[25, 26]} Particularly liquid-phase epitaxial (LPE) layer-by-layer (lbl) growth approach^{[27, 28]} affords an advanced approach to grow high-quality MOF thin films on the substrate surfaces (also known as surface-coordinated MOFs, SURMOFs) which promote the resulting MOF thin films to have the advantages of controllable growth orientation, tunable thickness and highly-homogeneous surface, providing a promising thin film material for the study in fundamental research and the application on sensors and devices applications. Especially, the development of SURMOFs with chiral function (called chiral SURMOF, SURchirMOFs) is very important for chiral related applications but their preparation was rarely reported. The previous work showed that the pillar-layered homochiral MOFs M₂(D/Lcam)₂L (M = Zn or Cu; D/Lcam = camphoric acid; L = pillared ligands) could easily grow chiral SURMOFs using LPE lbl methods.^{[29, 30]}

  As the emerging chiroptical applications, circularly polarized luminescence (CPL)^[31-34] of chiral thin films has aroused great interest.^{[35, 36]} Supramolecular self-assembly, upconversion materials and liquid crystals have been reported to achieve CPL amplification of 1~2 orders of magnitude.^[37-39] However, the use of MOF thin films to study CPL amplification has not been reported yet. In addition, MOFs with chiral feature have diverse structures, ordered nanopores and tunable functionalities, providing excellent candidates for developing CPL materials by selecting both inorganic and organic components. Particularly, SURchirMOFs have homogeneous films and can have large surface, resulting in good candidates for CPL applications. So far, organic molecules/supramolecular^[40-42] and the related chiral thin films have been widely studied for CPL. Recently, developing the chiral SURMOF forpromising chiroptical devices and sensors applications has attracted great interest in CPL study. For example, the first chiral SURMOFs, Zn₂(D/Lcam)₂DAP^[43] constructed with chiral ligand and luminescent ligand zapyrene-based was prepared on quartz substrates for CPL. However, the assembly of chiral SURMOFs consisting of chiral and luminescent ligands directly is difficult and the prediction of CPL properties is also challenging. Therefore, developing an efficient method to achieve or improve CPL of chiral SURMOFs is significant to expand CPL applications.

  Scheme 1

  

  Scheme 1.  The assembly process of Zn₂(Dcam)₂Pr-NH₂ and Zn₂(Dcam)₂Pr-NH-FITC prepared by lbl grafting method.

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  Based on above considerations, in this work a new pillar-layered homochiral SURMOF Zn₂(D/Lcam)₂Pr-NH₂ grown successfully on the substrate surfaces is composed of chiral ligand D- or L-camphoric acid (D/Lcam) and pillared ligand aminopyrazine (Pr-NH₂) using LPE lbl dipping method. More importantly, the chiral SURMOFs with amino group can be post-modified with thiocyanate containing fluorescent dye molecule to enhance CPL. The prepared SURchirMOF Zn₂(D/Lcam)₂Pr-NH₂ with high orientation and homogeneous surface exhibits good enantioselective adsorption toward limonene enantiomers and strong chirality but weak CPL emission at 390 nm. By using lbl-modifying approach, the FITC with green emission can be grafted on SURchirMOF Zn₂(D/Lcam)₂Pr-NH₂ skeleton by the lbl polyurethane reaction, which fails to use direct post-modification method. The modified SURchirMOF Zn₂(D/Lcam)₂Pr-NH-FITC keeps the chirality and shows CPL emission at about 540 nm. The present work provides a facile strategy to develop the chiral MOF thin films for CPL improvement by using lbl grafting fluorescent molecules.

  RESULTS AND DISCUSSION

  SURchirMOF Zn₂(Dcam)₂Pr-NH₂. The hydroxyl functionalized substrates (quartz substrates and Au wafer) are chosen as the SURMOFs growth in this work. A new SURchirMOF assembled by aminopyrazine and Dcam = (1R, 3S)-(+)-camphorate or Lcam = (1S, 3R)-(-)-camphorate, is prepared on the substrates using a LPE lbl approach, named Zn₂(D/Lcam)₂Pr-NH₂. As the homochiral MOF with pillar-layered structure, Zn₂(D/Lcam)₂ acts as the 2D layer, while the Pr-NH₂ serves as the bridging pillar.^[44] X-ray diffraction (XRD) patterns for the SURchirMOF Zn₂(D/Lcam)₂Pr-NH₂ in an out-of-plane mode (Figure 1(b)) show diffraction peaks at 9.2 and 18.4°, corresponding to the (100) and (200) peaks of simulated MOF. The in-plane XRD patterns of the samples at 9.3, 13.2, 14.8, and 18.8° are in accord with the simulated XRD peaks at (011), (002), (021), and (022). The XRD patterns clearly demonstrate a preferentially oriented growth of SURchirMOF Zn₂(D/Lcam)₂Pr-NH₂ along the [100] orientation, revealing a good agreement with the simulated XRD pattern calculated from the structures of Zn₂(Dcam)₂Pr-NH₂ (Figure 1(a)). The scanning electron microscopy (SEM) images (Figure 1(c)) of Zn₂(Dcam)₂Pr-NH₂ show a highly homogeneous crystalline film of the obtained SURchirMOF and the cross-sectional SEM image displays the thickness to be ~500 nm when the LPE lbl dipping cycles are 30. The infrared (IR) spectra (Figure 1(d)) for Zn₂(Dcam)₂Pr-NH₂ show that the appearance of the band at 1538 cm^-1 corresponds to C-O stretching vibration, and those at 1613 and 2976 cm^-1 belong to the C=O and N-H groups, respectively. The chiral characteristic of the SURMOFs is characterized by circular dichroism (CD) (Figure 1(e)) spectrometer. The CD spectra show that Zn₂(D/Lcam)₂Pr-NH₂ has a strong and opposite CD signal at ~230 nm in Zn₂(Dcam)₂Pr-NH₂ and Zn₂(Lcam)₂Pr-NH₂, indicating the chiral MOF thin films with enantiomers. In order to study the SURchirMOFs on enantioselectivity of enantiomers, a gas phase quartz crystal microbalance (QCM) technique is used to monitor mass changes with pure argon by detecting the change of resonance frequency, which has been developed for investigating the enantioselectivity of homochiral MOF thin films.^[45-47] The Au coated QCM electrode is used as the growth substrate. By using the lbl dipping method, the SURchirMOF Zn₂(Dcam)₂Pr-NH₂ is prepared for further experiment. The QCM adsorption results (Figure 1(f)) show that the adsorption amount of(R)- or (S)-limonene for Zn₂(Dcam)₂Pr-NH₂ is 1.74 and 0.88 μg cm^-2, which exhibit an ee value^{[48, 49]} (32.8%). The Zn₂(Lcam)₂Pr-NH₂ adsorption results exhibit enantioselective adsorption for (S)-limonene over (R)-limonene (ee = 42.4%) with 2.25 and 0.91 μg cm^-2 (Figure S1, 2), respectively. In addition, the photoluminescent spectra show the SURchirMOF Zn₂(Dcam)₂Pr-NH₂ has photoluminescent emission (Figure 3(b(2))) at 390 nm, which is different from the ligand Pr-NH₂ (Figure S3) (370 nm).

  Figure 1

  

  Figure 1.  (a) The structural model of Zn₂(Dcam)₂Pr-NH₂; (b) Out-of-plane and in-plane XRD patterns of Zn₂(Dcam)₂Pr-NH₂; (c) Surface and cross-sectional SEM images of Zn₂(Dcam)₂Pr-NH₂; (d) IR spectra of Zn₂(Dcam)₂Pr-NH₂; (e) CD spectra of Zn₂(D/Lcam)₂Pr-NH₂; (f) Comparison of (R)- or (S)-limonene adsorption uptakes for Zn₂(Dcam)₂Pr-NH₂ measured by QCM technique with the histogram of ee%.

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  Figure 2

  

  Figure 2.  (a) XRD pattern of Zn₂(Dcam)₂Pr-NH-FITC; (b) Surface SEM images of Zn₂(Dcam)₂Pr-NH-FITC; (c) The IR spectra of Zn₂(Dcam)₂Pr-NH₂ and Zn₂(Dcam)₂Pr-NH-FITC; (d) Ethanol adsorption uptake for Zn₂(Dcam)₂-Pr-NH₂ and Zn₂(Dcam)₂Pr-NH-FITC measured by QCM technology.

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  Figure 3

  

  Figure 3.  (a) The CD spectra of Zn₂(D/Lcam)₂Pr-NH-FITC; (b) The photoluminescent emission spectra of FITC (1), Zn₂(Dcam)₂Pr-NH₂ (2) and Zn₂(Dcam)₂Pr-NH-FITC (3); (c) The CPL spectra of Zn₂(D/Lcam)₂Pr-NH₂ and Zn₂(D/Lcam)₂Pr-NH-FITC and CPL dissymmetric factor (g_lum) of Zn₂(D/Lcam)₂Pr-NH₂ and Zn₂(D/Lcam)₂Pr-NH-FITC.

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  SURchirMOF Zn₂(Dcam)₂Pr-NH-FITC. In order to improve the CPL property of SURchirMOF Zn₂(D/Lcam)₂Pr-NH₂, here we further introduce the amino containing fluorescent dye molecules FITC by liquid-phase epitaxial lbl modification method, which is named Zn₂(Dcam)₂Pr-NH-FITC. The lbl-modified chiral thin film was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), IR spectra and UV-vis spectra. From the XRD patterns (Figure 2(a) and S4), we can find that the chiral thin film still has the preferential growth orientation after the lbl modification of dye molecule. Compared with the as-prepared SURchir-MOF Zn₂(Dcam)₂Pr-NH₂, the SEM images (Figure 2(b)) of SURchirMOF Zn₂(Dcam)₂Pr-NH-FITC show the flat and uniform morphology with 30 LPE lbl dipping cycles, and the extra absorbance bands at 1456, 1702 and 2914 cm^-1 of IR spectra (Figure 2(c)), as well as the increased absorption intensity at ~500 nm in UV-vis spectra (Figure S5), which proves that SURchirMOF Zn₂(Dcam)₂Pr-NH-FITC is lbl-modified by FITC dye successfully. The QCM adsorption amount of ethanol with the lbl-modified chiral thin film is significantly reduced compared with the as-prepared SURchirMOF Zn₂(Dcam)₂Pr-NH₂ from 2.1 to 1.4 μg cm^-2 (Figure 2(d)). Similarly, the same QCM adsorption result of ethanol uptake is obtained when comparing with that of SURchirMOF Zn₂(Lcam)₂Pr-NH₂ and Zn₂(Lcam)₂Pr-NH-FITC (Figure S6).

  Chiroptical Properties. To investigate the chiroptical properties of lbl-modified SURchirMOF Zn₂(D/Lcam)₂Pr-NH-FITC, the CD absorption spectra of SURchirMOF Zn₂(Dcam)₂Pr-NH-FITC display one positive band at ~230 nm and Zn₂(Lcam)₂Pr-NH-FITC thin film exhibits mirror images of CD signal (Figure 3(a)). In the test, to demonstrate that the CD and CPL signals are not influenced by linear dichroism and birefringence, we get average signal of front and back from one sample.^[50] As a green fluorescent dye molecule, FITC has good fluorescence property (Figure 3(b(3) ) and S7), which can promote the photoluminescent intensity of Zn₂(Dcam)₂Pr-NH₂ (Figure 3(b(2)) and S8, 9). As shown in Figure 3 (b(1)) and S10, 11), the photoluminescent spectra of SURchirMOF Zn₂(D/Lcam)₂Pr-NH-FITC exhibit an intense green emission with bands located at ~540 nm, with excitation at ~340 nm. In addition, the SURchirMOF Zn₂(D/Lcam)₂Pr-NH-FITC has strong CD signal, which is similar to SURchirMOF Zn₂(D/Lcam)₂Pr-NH₂. This also reveals that the lbl-modification of the SURchirMOF does not affect the chiral signal.

  The CPL spectra with almost mirror images for the enantiomers Zn₂(D/Lcam)₂Pr-NH₂ and Zn₂(D/Lcam)₂Pr-NH-FITC are found that both of them have CPL signal. As shown in Figure 3(c), Zn₂(Dcam)₂Pr-NH₂ exhibits negative CPL sign at 390 nm, while Zn₂(Lcam)₂Pr-NH₂ also shows positive CPL sign, with g_lum of about ±0.0003. Compared with as-prepared SURchirMOF Zn₂(D/Lcam)₂Pr-NH₂, Zn₂(D/Lcam)₂Pr-NH-FITC has a stronger CPL signal at ~540 nm under excitation of ~340 nm, showing a mirror image of green emission with g_lum of about ±0.001. This preparation strategy can effectively achieve energy transfer between FITC and SURchirMOF, resulting in an amplification of CPL performance.^{[51, 52]}

  In order to demonstrate the feasibility of this lbl grafting strategy, the as-prepared SURchirMOF Zn₂(Dcam)₂Pr-NH₂ is immersed into FITC solution for post-modification of dye molecule FITC, which is named Zn₂(Dcam)₂Pr-NH~FITC. Unfortunately, such post-modification strategy is not available in this SURchirMOF, which is demonstrated by the unchanged XRD, SEM, and IR as well as QCM adsorption of ethanol. The unchanged XRD patterns (Figure S12) show the crystallinity of MOF is maintained, which can also be seen in the SEM image (Figure S13). The IR spectra (Figure S14) of Zn₂(Dcam)₂Pr-NH~FITC are similar to that of as-prepared SURchirMOF Zn₂(Dcam)₂Pr-NH₂, and the almost unchanged QCM adsorption of ethanol (Figure S15) demonstrates that the dye (FITC) does not enter into the cavity of SURchirMOF to modify the skeleton of NH₂-funcationalized MOF. As a result, due to the small pore size of the chiral Zn₂(Dcam)₂Pr-NH₂, such post-modification strategy is unsuccessful for CPL enhancement of the chiral thin film.

  CONCLUSION

  In summary, the proof-of-concept chiral MOF thin films (SURchirMOFs) with CPL amplification have been successfully fabricated by lbl grafting luminescent dye molecules onto the skeleton of chirMOF thin films. By using LPE lbl dipping method, homochiral MOFs thin film containing free-coordinated amino group is successfully grown on the OH-functionalized substrates. The obtained Zn₂(D/Lcam)₂Pr-NH₂ SURchirMOF shows weak CPL performance. By lbl modification growth approach with the carboxyl containing dye molecule, the lbl-modified SURchirMOFs Zn₂(D/Lcam)₂Pr-NH-FITC have strong chirality and intense luminescent emission. The CPL spectra show that Zn₂(D/Lcam)₂Pr-NH-FITC exhibits obvious improvement performance on CPL, which is ~7 times stronger CPL signal and more than ~3 times g_lum value than that of Zn₂(D/Lcam)₂Pr-NH₂, comparable to the performance of the reported materials. The lbl-modified chiral SURMOFs provide an effective and facile strategy to achieve the CPL amplification on the MOF thin film materials.

  EXPERIMENTAL

  Materials and Methods. All the chemical reagents employed in this work were commercially available. Zinc acetate dihydrate (Zn(OAc)₂∙2H₂O, Sinopharm Chemical), Dcam = (1R, 3S)-(+)-camphorate, Lcam = (1S, 3R)-(-)-camphorate (C₁₀H₁₆O₄, Sigma-Aldrich, 99%), Pr-NH₂ = aminopyrazine (C₄H₅N₃, Aladdin, 99%), (R)- or (S)-limonene (TCI, 98%) and ethanol (C₂H₅OH, Sinopharm Chemical, 99.7%).

  The samples grown on Au substrate were characterized with powder X-ray diffraction (PXRD) analysis performed on a MiniFlex2 X-ray diffractometer using Cu-Kα radiation (λ = 0.1542 nm). The samples grown on functionalized Au/SiO₂ wafer and quartz substrates were characterized by Flourier transformation infrared (FTIR) spectra and scanning electron microscope (SEM). Fluore-scence photoluminescent spectra for the samples were performed on an Edinburgh Analytical instrument FLS920. The bare quartz substrate was used as the reference for CD, LD and CPL measurements. Circularly polarized luminescence (CPL) spectra were obtained using JASCO CPL-300.

  Mass uptake results of (R)- or (S)-limonene and ethanol for the samples grown on Au-coated QCM electrodes were obtained by BELQCM instrument.

  Substrate Pretreatment. The quartz substrates were cleaned and treated with a mixture of sodium hydrate (1 mM) and hydrogen peroxide (30%) with a volume ratio 3:1 at 80 ℃ for 30 minutes, as well as the Au and Au-coated QCM electrodes were immersed into 11-mercapto-1-undecanol (MUD) ethanolic solution (20 μM) at room temperature for 2 days, then cleaned with deionized water or ethanol and dried under nitrogen flux to obtain OH-functionalized substrates for the next preparation.

  Synthesis of SURchirMOF Zn₂(D/Lcam)₂Pr-NH₂. The SURchir-MOF Zn₂(D/Lcam)₂Pr-NH₂ was grown by the layer-by-layer (lbl) automatic dipping method and fabricated with the following ethanolic solutions at 50 ℃: 1.0 mM zinc acetate (Zn(OAc)₂), 0.4 mM H₂Dcam/H₂Lcam and 0.4 mM aminopyrazine (Pr-NH₂) mixed solution. The amount of solution can be enough to cover the substrate. The detailed experimental steps: firstly, functionalized quartz substrate was immersed in a solution of Zn(OAc)₂ for 15 min, and then was immersed in a solution of equimolar H₂Dcam/H₂Lcam and a Pr-NH₂ mixed solution for 20 min. After each step, the sample was washed with pure ethanol for 2 min to remove residual reactants. The above details represent one growth cycle. The ChirMOF Zn₂(D/Lcam)₂Pr-NH₂ thin films were obtained by 30 growth cycles.

  Synthesis of SURchirMOF Zn₂(D/Lcam)₂Pr-NH-FITC. The SURchirMOF Zn₂(D/Lcam)₂Pr-NH-FITC was synthesized by the layer-by-layer automatic dipping method at 50 ℃. The functionalized quartz substrates were immersed in 1.0 mM Zn(OAc)₂, 0.4 mM equimolar H₂Dcam/H₂Lcam, Pr-NH₂ and 0.1 mM fluorescein isothiocyanate with the immersion time to be 20, 30, and 10 min, respectively. A total of 30 growth cycles are used for the Zn₂(D/Lcam)₂Pr-NH-FITC thin films.

  Quartz Crystal Microbalance Adsorption of the Thin Films. The quartz crystal microbalance (QCM) has been used to monitor the mass of probe species with good volatility in gas phase by monitoring the resonance frequency changes on the electrode thin film. The gold-coated QCM sensors used as substrates were functionalized by 11-mercapto-1-undecanol (MUD) SAMs. The 20 cycles SURchirMOF Zn₂(D/Lcam)₂Pr-NH₂ and Zn₂(D/Lcam)₂Pr-NH-FITC were prepared on the substrates using the same condition and growth procedure mentioned above. In this work, the pure argon was used for the baseline, (R)- or (S)-limonene and ethanol were chosen as the loading analyte.

  
  ACKNOWLEDGEMENTS: This work was supported by the National Natural Science Foundation of China (21872148), the Youth Innovation Promotion Association of the Chinese Academy of Sciences (2018339), and Fujian Science & Technology Innovation Laboratory for Optoelectronic Information of China (2021ZR131). COMPETING INTERESTS
  The authors declare no competing interests.
  For submission: https://www.editorialmanager.com/cjschem
  Supplementary information is available for this paper at http://manu30.magtech.com.cn/jghx/EN/10.14102/j.cnki.0254-5861.2022-0023.
  ADDITIONAL INFORMATION
  
• 1. [1]

     Wang, S. Z.; McGuirk, C. M.; d'Aquino, A.; Mason, J. A.; Mirkin, C. A. Metal-organic framework nanoparticles. Adv. Mater. 2018, 30, 1800202. doi: 10.1002/adma.201800202

  2. [2]

     Yuan, S.; Feng, L.; Wang, K. C.; Pang, J. D.; Bosch, M.; Lollar, C.; Sun, Y. J.; Qin, J. S.; Yang, X. Y.; Zhang, P.; Wang, Q.; Zou, L. F.; Zhang, Y. M.; Zhang, L. L.; Fang, Y.; Li, J. L.; Zhou, H. C. Stable metal-organic frameworks: design, synthesis and applications. Adv. Mater. 2018, 30, 1704303.

  3. [3]

     Li, H.; Eddaoudi, M.; O'Keeffe, M.; Yaghi, O. M. Design and synthesis of an exceptionally stable and highly porous metal-organic framework. Nature 1999, 402, 276-279.

  4. [4]

     Chae, H. K.; Eddaoudi, M.; Kim, J.; Hauck, S. I.; Hartwig, J. F.; O'Keeffe, M.; Yaghi, O. M. Tertiary building units: synthesis, structure, and porosity of a metal-organic dendrimer framework (MODF-1). J. Am. Chem. Soc. 2001, 123, 11482-11483. doi: 10.1021/ja011692+

  5. [5]

     Witters, D.; Vergauwe, N.; Ameloot, R.; Vermeir, S.; De Vos, D.; Puers, R.; Sels, B.; Lammertyn, J. Digital microfluidic high-throughput printing of single metal-organic framework crystals. Adv. Mater. 2012, 24, 1316-1320.

  6. [6]

     Zou, M. L.; Dai, W. L.; Mao, P.; Li, B.; Mao, J.; Zhang, S. Q.; Yang, L. X.; Luo, S. L.; Luo, X. B.; Zou, J. P. Integration of multifunctionalities on ionic liquid-anchored MIL-101(Cr): a robust and efficient heterogeneous catalyst for conversion of CO₂ into cyclic carbonates. Micropor. Mesopor. Mat. 2021, 312, 110750. doi: 10.1016/j.micromeso.2020.110750

  7. [7]

     Teufel, J.; Oh, H.; Hirscher, M.; Wahiduzzaman, M.; Zhechkov, L.; Kuc, A.; Heine, T.; Denysenko, D.; Volkmer, D. MFU-4-A metal-organic framework for highly effective H₂/D₂ separation. Adv. Mater. 2013, 25, 635-639.

  8. [8]

     Chen, R. Z.; Yao, J. F.; Gu, Q. F.; Smeets, S.; Baerlocher, C.; Gu, H. X.; Zhu, D. R.; Morris, W.; Yaghi, O. M.; Wang, H. T. A two-dimensional zeolitic imidazolate framework with a cushion-shaped cavity for CO₂ adsorption. Chem. Commun. 2013, 49, 9500-9502. doi: 10.1039/c3cc44342f

  9. [9]

     Li, G. P.; Li, Z. Z.; Xie, H. F.; Fu, Y. L.; Wang, Y. Y. Efficient C₂ hydrocarbons and CO₂ adsorption and separation in a multi-site functionalized MOF. Chin. J. Struct. Chem. 2021, 40, 1047-1054.

  10. [10]

      Yu, H. Y.; Liu, J. C.; Bao, S.; Gao, G. Y.; Zhu, H. Y.; Zhu, P. F.; Wang, G. F. Luminescent lanthanide single atom composite materials: tunable full-color single phosphor and applications in white LEDs. Chem. Eng. J. 2022, 430, 132782.

  11. [11]

      Qin, L.; Guan, X. G.; Yang, C.; Huang, J. S.; Che, C. M. Near-infrared phosphorescent supramolecular alkyl/aryl-iridium porphyrin assemblies by axial coordination. Chem. Eur. J. 2018, 24, 14400-14408.

  12. [12]

      Wu, D. F.; Guo, Z. Y.; Yin, X. B.; Pang, Q. Q.; Tu, B. B.; Zhang, L. J.; Wang, Y. G.; Li, Q. W. Metal-organic frameworks as cathode materials for Li-O-2 batteries. Adv. Mater. 2014, 26, 3258-3262.

  13. [13]

      Zhou, X. L.; Jin, H. Y.; Xia, B. Y.; Davey, K.; Zheng, Y.; Qiao, S. Z. Molecular cleavage of metal-organic frameworks and application to energy storage and conversion. Adv. Mater. 2021, 33, 2104341.

  14. [14]

      Wu, C. D.; Lin, W. B. A chiral porous 3D metal-organic framework with an unprecedented 4-connected network topology. Chem. Commun. 2005, 3673-3675.

  15. [15]

      Han, Z. S.; Shi, W.; Cheng, P. Synthetic strategies for chiral metal-organic frameworks. Chin. Chem. Lett. 2018, 29, 819-822.

  16. [16]

      Song, F. J.; Wang, C.; Lin, W. B. A chiral metal-organic framework for sequential asymmetric catalysis. Chem. Commun. 2011, 47, 8256-8258.

  17. [17]

      Zhang, H.; Lou, L. L.; Yu, K.; Liu, S. X. Advances in chiral metal-organic and covalent organic frameworks for asymmetric catalysis. Small 2021, 17, 20055686.

  18. [18]

      Das, S.; Xu, S. X.; Ben, T.; Qiu, S. L. Chiral recognition and separation by chirality-enriched metal-organic frameworks. Angew. Chem. Int. Ed. 2018, 57, 8629-8633.

  19. [19]

      He, Y. P.; Tan, Y. X.; Zhang, J. Gas sorption, second-order nonlinear optics, and luminescence properties of a multifunctional srs-type metal-organic framework built by tris(4-carboxylphenylduryl)amine. Inorg. Chem. 2015, 54, 6653-6656.

  20. [20]

      Qu, M.; Liu, M. M.; Liu, J.; Zhang, X. M. Tunable nonlinear optical property and photocatalytic activity on luminescent chiral lanthanide chains. Chin. J. Chem. 2014, 32, 1259-1266.

  21. [21]

      Sun, C. Y.; Qin, C.; Wang, C. G.; Su, Z. M.; Wang, S.; Wang, X. L.; Yang, G. S.; Shao, K. Z.; Lan, Y. Q.; Wang, E. B. Chiral nanoporous metal-organic frameworks with high porosity as materials for drug delivery. Adv. Mater. 2011, 23, 5629-5632.

  22. [22]

      Qu, X. L.; Yan, B. Zn(Ⅱ)/Cd(Ⅱ)-based metal-organic frameworks: crystal structures, Ln(Ⅲ)-functionalized luminescence and chemical sensing of dichloroaniline as a pesticide biomarker. J. Mater. Chem. C 2020, 8, 9427-9439.

  23. [23]

      Kuang, X.; Ye, S. J.; Li, X. Y.; Ma, Y.; Zhang, C. Y.; Tang, B. A new type of surface-enhanced raman scattering sensor for the enantioselective recognition of D/L-cysteine and D/L-asparagine based on a helically arranged Ag NPs@homochiral MOF. Chem. Commun. 2016, 52, 5432-5435.

  24. [24]

      Seo, J. S.; Whang, D.; Lee, H.; Jun, S. I.; Oh, J.; Jeon, Y. J.; Kim, K. A homochiral metal-organic porous material for enantioselective separation and catalysis. Nature 2000, 404, 982-986.

  25. [25]

      Li, D.; Liu, X. T.; Wu, W. T.; Peng, Y.; Zhao, S. G.; Li, L. N.; Hong, M. C.; Luo, J. H. Chiral lead-free hybrid perovskites for self-powered circularly polarized light detection. Angew. Chem. Int. Ed. 2021, 133, 8496-8499.

  26. [26]

      Chen, M.; Qin, A. J.; Lam, J. W. Y.; Tang, B. Z. Multifaceted functionalities constructed from pyrazine-based AIEgen system. Coord. Chem. Rev. 2020, 422, 213472.

  27. [27]

      Mandemaker, L. D. B.; Rivera-Torrente, M.; Geitner, D. R.; Vis, C. M.; Weckhuysen, B. M. In situ spectroscopy of calcium fluoride anchored metal-organic framework thin films during gas sorption. Angew. Chem. Int. Ed. 2020, 59, 19545-19552.

  28. [28]

      Kang, Z. X.; Fan, L. L.; Sun, D. F. Recent advances and challenges of metal-organic framework membranes for gas separation. J. Mater. Chem. A 2017, 5, 10073-10091.

  29. [29]

      Xiao, Y. H.; Gu, Z. G.; Zhang, J. Surface-coordinated metal-organic framework thin films (SURMOFs) for electrocatalytic applications. Nanoscale 2020, 12, 12712-12730.

  30. [30]

      Semrau, A. L.; Zhou, Z. Y.; Mukherjee, S.; Tu, M.; Li, W. J.; Fischer, R. A. Surface-mounted metal-organic frameworks: past, present and future perspectives. Langmuir 2021, 37, 6847-6863.

  31. [31]

      Zong, Z. H.; Zhang, P.; Qiao, H. W.; Hao, A. Y.; Xing, P. Y. Chiral toroids and tendril superstructures from integrated ternary species with consecutively tunable supramolecular chirality and circularly polarized luminescence. J. Mater. Chem. C 2020, 8, 16224-16233.

  32. [32]

      Zou, C.; Qu, D.; Jiang, H. J.; Lu, D.; Ma, X. T.; Zhao, Z. Y.; Xu, Y. Bacterial cellulose: a versatile chiral host for circularly polarized luminescence. Molecules 2019, 24, 1008.

  33. [33]

      Sang, Y.; Han, J.; Zhao, T.; Duan, P. F.; Liu, M. H. Circularly polarized luminescence in nanoassemblies: generation, amplification and application. Adv. Mater. 2020, 32, 1900110.

  34. [34]

      Albano, G.; Pescitelli, G.; Di Bari, L. Chiroptical properties in thin films of pi-conjugated systems. Chem. Rev. 2020, 120, 10145-10243.

  35. [35]

      Hirahara, T.; Yoshizawa-Fujita, M.; Takeoka, Y.; Rikukawa, M. Highly efficient circularly polarized light emission in the green region from chiral polyfluorene-thiophene thin films. Chem. Lett. 2012, 41, 905-907.

  36. [36]

      Pan, M.; Zhao, R.; Zhao, B.; Deng, J. P. Two chirality transfer channels assist handedness inversion and amplification of circularly polarized luminescence in chiral helical polyacetylene thin films. Macromolecules 2021, 54, 5043-5052.

  37. [37]

      Zheng, S.; Han, J.; Jin, X.; Ye, Q.; Zhou, J.; Duan, P.; Liu, M.; Halogen bonded chiral emitters: generation of chiral fractal architecture with amplified circularly polarized luminescence. Angew. Chem. Int. Ed. 2021, 60, 22711-22716.

  38. [38]

      Yang, X. F.; Han, J. L.; Wang, Y. F.; Duan, P. F. Photon-upconverting chiral liquid crystal: significantly amplified upconverted circularly polarized luminescence. Chem. Sci. 2019, 10, 172-178.

  39. [39]

      Chen, Y.; Lu, P.; Gui, Q.; Li, Z.; Yuan, Y.; Zhang, H. Preparation of chiral luminescent liquid crystal and manipulation of phase structures on circularly polarized luminescence property. J. Mater. Chem. C 2021, 9, 1279-1286.

  40. [40]

      Zhang, H. W.; Han, J. L.; Jin, X.; Duan, P. F. Improving the overall properties of circularly polarized luminescent materials through areneperfluoroarene interactions. Angew. Chem. Int. Ed. 2021, 60, 4575-4580.

  41. [41]

      Yang, Y.; da Costa, R. C.; Smilgies, D. M.; Campbell, A. J.; Fuchter, M. J. Induction of circularly polarized electroluminescence from an achiral light-emitting polymer via a chiral small molecule dopant. Adv. Mater. 2013, 25, 2624-2628.

  42. [42]

      Shi, N.; Tan, J. Y.; Wan, X. H.; Guan, Y.; Zhang, J. Induced saltresponsive circularly polarized luminescence of hybrid assemblies based on achiral Eu-containing polyoxometalates. Chem. Commun. 2017, 53, 4390-4393.

  43. [43]

      Chen, S. M.; Chang, L. M.; Yang, X. K.; Luo, T.; Xu, H.; Gu, Z. G.; Zhang, J. Liquid-phase epitaxial growth of azapyrene-based chiral metal-organic framework thin films for circularly polarized luminescence. ACS Appl. Mater. Interfaces 2019, 11, 31421-31426.

  44. [44]

      Rood, J. A.; Noll, B. C.; Henderson, K. W. A homochiral metal-organic framework with amino-functionalized pores. Main Group Chem. 2009, 8, 237-250.

  45. [45]

      Zhai, R.; Xiao, Y. H.; Gu, Z. G.; Zhang, J. Tunable chiroptical application by encapsulating achiral lanthanide complexes into chiral MOF thin films. Nano Res. 2022, 15, 1102-1108.

  46. [46]

      Li, C.; Heinke, L. Thin films of homochiral metal-organic frameworks for chiroptical spectroscopy and enantiomer separation. Symmetry-Basel 2020, 12, 686.

  47. [47]

      Chen, S. M.; Liu, M.; Gu, Z. G.; Fu, W. Q.; Zhang, J. Chiral chemistry of homochiral porous thin film with different growth orientations. ACS Appl. Mater. Interfaces 2016, 8, 27332-27338.

  48. [48]

      Zhao, J. S.; Li, H. W.; Han, Y. Z.; Li, R.; Ding, X. S.; Feng, X.; Wang, B. Chirality from substitution: enantiomer separation via a modified metal-organic framework. J. Mater. Chem. A 2015, 3, 12145-12148.

  49. [49]

      Lu, Y. Z. H.; Zhang, H. C.; Chan, J. Y.; Ou, R. W.; Zhu, H. J.; Forsyth, M.; Marijanovic, E. M.; Doherty, C. M.; Marriott, P. J.; Holl, M. M. B.; Wang, H. T. Homochiral MOF-polymer mixed matrix membranes for efficient separation of chiral molecules. Angew. Chem. Int. Ed. 2019, 58, 16928-16935.

  50. [50]

      Albano, G.; Salerno, F.; Portus, L.; Porzio, W.; Aronica, L. A.; DiBari, L. Outstanding chiroptical features of thin films of chiral oligothiophenes. ChemNanoMat 2018, 4, 1059-1070.

  51. [51]

      Zhang, C.; Yan, Z. P.; Dong, X. Y.; Han, Z.; Li, S.; Fu, T.; Zang, S. Q. Enantiomeric MOF crystals using helical channels as palettes with bright white circularly polarized luminescence. Adv. Mater. 2020, 32, 2002914.

  52. [52]

      Zhao, T.; Han, J.; Jin, X.; Zhou, M.; Liu, Y.; Duan, P. F.; Liu, M. H. Dual-mode induction of tunable circularly polarized luminescence from chiral metal-organic frameworks. Research 2020, 2020, 1-12.

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  Scheme 1  The assembly process of Zn₂(Dcam)₂Pr-NH₂ and Zn₂(Dcam)₂Pr-NH-FITC prepared by lbl grafting method.

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  Figure 1  (a) The structural model of Zn₂(Dcam)₂Pr-NH₂; (b) Out-of-plane and in-plane XRD patterns of Zn₂(Dcam)₂Pr-NH₂; (c) Surface and cross-sectional SEM images of Zn₂(Dcam)₂Pr-NH₂; (d) IR spectra of Zn₂(Dcam)₂Pr-NH₂; (e) CD spectra of Zn₂(D/Lcam)₂Pr-NH₂; (f) Comparison of (R)- or (S)-limonene adsorption uptakes for Zn₂(Dcam)₂Pr-NH₂ measured by QCM technique with the histogram of ee%.

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  Figure 2  (a) XRD pattern of Zn₂(Dcam)₂Pr-NH-FITC; (b) Surface SEM images of Zn₂(Dcam)₂Pr-NH-FITC; (c) The IR spectra of Zn₂(Dcam)₂Pr-NH₂ and Zn₂(Dcam)₂Pr-NH-FITC; (d) Ethanol adsorption uptake for Zn₂(Dcam)₂-Pr-NH₂ and Zn₂(Dcam)₂Pr-NH-FITC measured by QCM technology.

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  Figure 3  (a) The CD spectra of Zn₂(D/Lcam)₂Pr-NH-FITC; (b) The photoluminescent emission spectra of FITC (1), Zn₂(Dcam)₂Pr-NH₂ (2) and Zn₂(Dcam)₂Pr-NH-FITC (3); (c) The CPL spectra of Zn₂(D/Lcam)₂Pr-NH₂ and Zn₂(D/Lcam)₂Pr-NH-FITC and CPL dissymmetric factor (g_lum) of Zn₂(D/Lcam)₂Pr-NH₂ and Zn₂(D/Lcam)₂Pr-NH-FITC.

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