N₂H₄Zn(HC₃N₃O₃): exceptionally strong second harmonic generation and ultra-long phosphorescence

Abstract

The discovery and designed synthesis of multifunctional materials is a leading pursuit in materials science. Herein, we report a novel hydro-isocyanurate, N₂H₄Zn(HC₃N₃O₃), which combines strong second harmonic generation (SHG) and ultra-long room-temperature phosphorescence (RTP). The SHG intensity is the highest within the cyanurate system (13 × KDP), and RTP lifetime extends up to 448 ms, accompanied by a long-lasting afterglow visible to the naked eye for 1.2 s, surpassing most of the current metal–organic complexes. This advancement holds promise for the development of multifunctional optoelectronic devices, particularly leveraging second-harmonic generation (SHG) processes.

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Introduction

The field of nonlinear optical (NLO) materials has been at the forefront of materials science, driving innovation in frequency conversion technologies such as second harmonic generation (SHG), which find wide applications in everyday life and industry.^1–5 On the other hand, materials that exhibit long-lived room-temperature phosphorescence (RTP) have been a great challenge. The rarity of materials that can stably maintain ultra-long RTP alongside strong SHG properties is primarily attributed to the complex interplay required between structural asymmetry for SHG activity and the delicate balance of energy states necessary for long-lived phosphorescence.^6–11 This dual functionality is highly desirable for applications ranging from secure optical communication to precise bio-imaging.^12–15

Semi-organic NLO crystals emerge as a promising class of materials that combine the processability and tunability of organic components with the structural stability of their inorganic counterparts.^16–27 Herein, we report a novel semi-organic crystal, N₂H₄Zn(HC₃N₃O₃), exhibiting exceptionally strong SHG and ultra-long RTP. The design rationale was to exploit the synergistic combination of a SHG-active (HC₃N₃O₃)²⁻ building unit with the coordination tendency of Zn²⁺ and the unique neutral N₂H₄ ligand. This assembly not only results in a non-centrosymmetric (NCS) structure conducive to SHG activity but also facilitates efficient exciton transfer and intersystem crossing (ISC), essential for RTP. The SHG of N₂H₄Zn(HC₃N₃O₃) is the strongest among that of metal cyanurates to date, surpassing that of KDP by a factor of 13, and it has an RTP lifetime of 448 ms, which is exceptionally long for metal complexes. Moreover, the material exhibits a visibly bright blue and green afterglow for up to 1.2 s. N₂H₄Zn(HC₃N₃O₃) also shows a large bandgap of 5.38 eV, a thermal stability up to 250 °C, insensitivity to air, robust resistance to water as well as a notable birefringence (Δn) of 0.29 @ 546 nm, which further underscore its practicality. Finally, theoretical calculations and analyses are conducted to understand the observed phenomena, offering insights into the future design synthesis of multifunctional materials.

Results and discussion

Block-like single crystals of N₂H₄Zn(HC₃N₃O₃), measuring up to 5 × 2 × 1 mm³, were successfully synthesized using a hydrothermal stoichiometric reaction of CH₆N₄·HNO₃, ZnBr₂, C₃H₃N₃O₃, and H₂O (Fig. S1†). The purity of the product was confirmed by using the fully assigned experimental powder X-ray diffraction (PXRD) data, which agree well with the single-crystal X-ray diffraction (SC-XRD) refinement results (Fig. S2†).

N₂H₄Zn(HC₃N₃O₃) crystallizes in the monoclinic polar Cc space group (Tables S1–S4†). The CCDC number is 2331157. The structure of N₂H₄Zn(HC₃N₃O₃) is a novel one, in which the Zn-centered tetrahedra are connected in a diamond-like topological three-dimensional (3D) framework (Fig. 1a) via the infinite anionic chains of ([Zn²⁺(HC₃N₃O₃)²⁻]_∞) (Fig. 1b) extending along the c-axis that are interwoven with the infinite cationic chains of ([Zn(N₂H₄)]_∞²⁺) (Fig. 1c), together with hydrogen bonds (Table S5†). Within this network, the Zn–Zn distance (bridged by two (HC₃N₃O₃)²⁻ rings) is 5.71 Å or 4.33 Å (bridged by two [N₂H₄] molecules) (Fig. 1c). Each Zn1 atom is tetrahedrally coordinated to two distinct (HC₃N₃O₃)²⁻ 6-MRs (Zn1–N1/3 bond lengths range from 1.973 Å to 1.982 Å) and two [N₂H₄] molecules (Zn1–N4/5 bond lengths are in the range of 2.054 Å to 2.070 Å), resulting in the formation of the highly polarized [Zn(HC₃N₃O₃)₂(N₂H₄)₂] tetrahedron (Fig. 1d). The Zn–N bond coordinated to the neutral hydrazine groups is slightly longer than that to the (HC₃N₃O₃)²⁻ ring, which is mainly due to the mutual electrostatic attraction between Zn²⁺ and (HC₃N₃O₃)²⁻ ( and S3†). Considering the bond valence sum (BVS) calculation results (Table S6†) and the coordination environment of the Zn atom, the H atoms are added to N2 by geometry optimization, giving a hydro-isocyanuric anionic group, (HC₃N₃O₃)²⁻. Within the (HC₃N₃O₃)²⁻ group, the C–N bond lengths span a range from 1.357(4) to 1.374(4) Å. In contrast, the C–O bond varies in a slightly broader range, extending from 1.225(4) to 1.247(5) Å. Furthermore, the N–N bond within the [N₂H₄] molecule is 1.457(4) Å. These bond distances agree well with those reported.^28,29

Fig. 1 (a) Highly diamond-like topology for [Zn(HC₃N₃O₃)₂(N₂H₄)₂]. (b) [Zn²⁺(HC₃N₃O₃)²⁻]_∞ infinite chains. (c) [Zn(N₂H₄)]_∞²⁺ infinite chains. (d) The highly polarized [Zn(HC₃N₃O₃)₂(N₂H₄)₂] tetrahedron. (e) The spatial arrangement of the polarized [Zn(HC₃N₃O₃)₂(N₂H₄)₂] groups (the red dashed box represents [Zn²⁺(HC₃N₃O₃)²⁻]_∞ infinite chains, and the orange dashed box represents [Zn(N₂H₄)]_∞²⁺ infinite chains). (f) The spatial arrangement of the polarized [Zn(HC₃N₃O₃)₂(N₂H₄)₂] groups (obtained by rotating the f-diagram by 90°).

In this structure, two differently oriented π-conjugated delocalized (HC₃N₃O₃)²⁻ groups are present, and the dihedral angle between the two (HC₃N₃O₃)²⁻ groups is 40.9° (Fig. S4†), while the intersection angle between two [N₂H₄] molecules is 38° (Fig. S5†). The [Zn(HC₃N₃O₃)₂(N₂H₄)₂] tetrahedron is highly polarized and constructs the diamond-like 3D network (Fig. 1e and f). Due to the absence of an inversion center in the polar Cc space group, all the polarized [Zn(HC₃N₃O₃)₂(N₂H₄)₂] groups align uniformly facilitating significant anisotropy and effective superposition of 2nd nonlinear susceptibility.

The optical properties of N₂H₄Zn(HC₃N₃O₃) were measured through infrared (IR), ultraviolet-visible (UV-vis) and photoluminescence (PL) spectroscopies. The IR stretching vibrations between N–H nitrogen and N–H⋯O at 2700–3500 and 792 cm⁻¹ are observed. The vibrations at 1400–1700 cm⁻¹ are attributed to (HC₃N₃O₃)²⁻, and those at 1157 and 1374 cm⁻¹ are attributed to C–O and C–N, respectively. These are the typical spectral features for cyanurate and isocyanurate derivatives (Fig. S6†). The UV-vis spectrum reveals a cutoff edge at 217 nm (E_g = 5.38 eV), the shortest in the hydro-isocyanurate family (Fig. 2a).

Fig. 2 Optical properties of N₂H₄Zn(HC₃N₃O₃): (a) UV-vis diffuse reflectance spectrum; inset: the experimental band gap calculated with the Kubelka–Munk functional. (b) The calculated refractive indices. (c) Particle-size-dependent SHG intensity under 1064 nm laser irradiation (d) Oscilloscope traces of the SHG signals for polycrystalline samples with a particle size range of 180–280 μm.

The birefringence (Δn) properties of N₂H₄Zn(HC₃N₃O₃) were measured on an as-obtained crystal with a thickness of 4.71 μm by using a polarized optical microscope fitted with a Berek compensator, illuminated with a 589 nm monochromatic green light source. The extinction process, facilitated by optical compensation, yielded a retardation value of −1387.3 nm, giving a Δn_obv. of 0.294 (Fig. S7†). The Δn_cal. = 0.306 @ 589 nm in principle agrees well with this observation (Fig. 2b). The Δn_obv. is comparable with those of other cyanurates and isocyanurates, such as Pb₂Cd(HC₃N₃O₃)₂(OH)₂ (0.291@800 nm), LiRbHC₃N₃O₃·2H₂O (0.259@532 nm) and NaRb_0.84Cs_0.16HC₃N₃O₃·2H₂O (0.238@532 nm) (Table S7†).^29–34 The large Δn of the title compound N₂H₄Zn(HC₃N₃O₃) may arise mainly from the strong anisotropy and π–π conjugation interactions of the (HC₃N₃O₃)²⁻ rings.

The particle-size-dependent SHG responses were measured by the Kurtz–Perry powder method utilizing a 1064 nm fundamental laser with KDP as a reference. The SHG responses of polycrystalline N₂H₄Zn(HC₃N₃O₃) samples intensify with increasing particle size, reaching a plateau at approximately 180 μm, indicating a phase matching behavior (Fig. 2c). The maximal SHG response is 13 times that of KDP, the strongest intensity among cyanurates (Fig. 2d and Table S8†).^35–40

The thermal stability and water and air resistance were studied. Unlike many isocyanurates, N₂H₄Zn(HC₃N₃O₃) possesses an anhydrous 3D network structure and is thermally stable until 250 °C without undergoing decomposition (Fig. S8†). Moreover, after a six-month exposure to ambient air and humidity, the crystals remained unfazed, showing no signs of degradation or moisture absorption. As shown in Fig. 3, the color and weight of N₂H₄Zn(HC₃N₃O₃) crystals remained unchanged after immersion in water for 10 days, and their the XRD patterns show no change before and after the immersion (Fig. S2†). Such a water treatment does not influence the green SHG light (532 nm) emission (Fig. 3).

Fig. 3 Water resistance test of the as-synthesized N₂H₄Zn(HC₃N₃O₃) crystal (the crystal emits green light at 532 nm when irradiated by using a 1064 nm laser).

The room-temperature photoluminescence properties were investigated. The fluorescence displays a broad emission band peaking at approximately 360 nm, corresponding to an excitation wavelength of 310 nm (Fig. S9†). Subsequent phosphorescence spectroscopy (Fig. 4c) indicated a dynamic red-shift in the emission peak position as the excitation wavelength was incrementally varied from 290 to 410 nm. This shift was observed to transition from around 460 nm to a range between 460 and 565 nm, marking emission adaptability. Fig. 4 depicts the dual-color emission capability; with an excitation wavelength of 310 nm, the emission peak is situated at around 460 nm indicative of blue light, while at 365 nm, the peak red-shifts to approximately 500 nm, corresponding to green light. This bioluminescence is corroborated by the 1931 International Commission on Radiation (CIE) chromaticity diagram (Fig. 4d). The naked-eye can distinctly perceive a persistent blue and green phosphorescent glow for about 1.2 s post-irradiation (Fig. 5d). The luminescence decay curves (Fig. 5a and b) further elucidate the multi-exponential decay behavior. The phosphorescence lifetimes are measured to be 448 ms and 428 ms for excitation wavelengths of 310 nm and 365 nm, respectively, with an average lifetime exceeding 400 ms. This longevity is superior to most organic–Zn metal complexes (Table S9† and Fig. 5c).^41–47 Simultaneously, the temperature-dependent luminescence measurements have elucidated that the phosphorescence intensity of the sample escalates incrementally as the experimental temperature diminishes, corroborating the typical characteristics of phosphorescence phenomena (Fig. S10†).

Fig. 4 The phosphorescence spectra of N₂H₄Zn(HC₃N₃O₃). The emission spectra at (a) 310 nm; (b) 365 nm. (c) The emission spectrum from 290 to 410 nm. (d) CIE color chromaticity under excitation from 310 to 365 nm.

Fig. 5 The decay curves for N₂H₄Zn(HC₃N₃O₃) at (a) 310 nm and (b) 365 nm. (C) The comparison of the phosphorescence lifetime of 11 selected compounds: [Zn₄(HEDP)₂(TIMB)]·H₂O (1), (Ph₃S)₂ZnCl₄ (2), (Ph₃S)₂MnCl₄ (3), [NH₃Me]·[Zn₂(HEDP)(TPA)_0.5(H₂O)₂]·2H₂O (4), [Zn₅(BIPA)₄MIM(OH)₂(H₂O)₂] (5), [Zn₃(BIPA)₂(MIM)₃(OH)₂]·2H₂O (6), Zn(HCOO)₂(4,4′-bipy) (7), ZnCl₂·R-2-MP (8), ZnCl₂·S-2-MP (9), Na₂Zn₂(C₉H₃O₆)₂(H₂O)₈·3H₂O (10) and the title compound (11). (d) Photographs of N₂H₄Zn(HC₃N₃O₃) before and after removing the 310 and 365 nm UV lamp.

To elucidate the relationship between the structure and properties of N₂H₄Zn(HC₃N₃O₃), first-principles calculations were conducted using the CASTEP software package.⁴⁸ The electronic band structure indicates that the valence band maximum (VBM) is positioned at the A point, and the conduction band minimum (CBM) is located at the M point, signifying a direct band gap of 4.60 eV (Fig. S11†). Given the tendency for the band gap to be underestimated due to the discontinuity in the exchange-correlation energy functional, a scissor operator of 0.78 eV was employed for subsequent optical property calculations. The total and partial densities of states (DOS) reveal that the band gap is predominantly dictated by the interactions between C-2p and O-2p orbitals, as well as the C-2p and N-2p orbitals within the [HC₃N₃O₃]²⁻ anionic group. The band associated with Zn-4s, 3d, and 3p states, and the N-2p state within the [N₂H₄] group, are primarily located in the lower energy region ranging from −10 to −5 eV and contributes minimally around the Fermi level (Fig. S12†). The electron distribution curves of the VBM and CBM (Fig. 6a and d) suggest that the VBM is mainly composed of O-n states, while the CBM is mainly derived from the (HC₃N₃O₃)²⁻-π* states. Thus, the organic component (HC₃N₃O₃)²⁻ contributes to both the CBM and VBM by promoting n–π* leaps, which, according to the EI-Sayed rule, can effectively promote inter-system crossing (ISC) in favor of ultra-long room-temperature phosphorescence, which is consistent with the proposed organic emission mechanism.

Fig. 6 The electron distribution profiles of N₂H₄Zn(HC₃N₃O₃): the (a) VBM and (c) CBM. SHG weight factor analysis of the d₁₁ component of the N₂H₄Zn(HC₃N₃O₃) crystal (b) and (d).

Previous studies reveal that the N-2p orbitals in cyanuric 6-MRs can experience a down-shift in their band structure when the bridging N atoms coordinate with H or Zn atoms, leading to an enlarged band gap for Zn(H₂C₃N₃O₃)2·3H₂O.²⁸ In the case of the title N₂H₄Zn(HC₃N₃O₃) compound, one of the bridging N atoms forms a N–H bond, while the other two bridge N atoms coordinate with two distinct Zn atoms to form Zn–N bonds. This arrangement effectively diminishes the N-2p electronic states near the Fermi level, leading to a band gap of 5.38 eV.

The refractive index calculations revealed a distinct n_z – n_y < n_y – n_x relationship, characterizing N₂H₄Zn(HC₃N₃O₃) as a negative biaxial crystal. The calculated birefringence of 0.306@589 nm is in close agreement with the Δn_obv. = 0.294@589 nm. The real-space atom-cutting calculations indicate that the (HC₃N₃O₃)²⁻ anionic groups contribute primarily to the optical anisotropy with a substantial 0.340@589 nm. Meanwhile, Zn²⁺ and the [N₂H₄] molecule have non-negligible but small contributions of 0.079 and 0.049@589 nm, respectively (Table S10†).

Utilizing the Kleinman approximation for point group m, N₂H₄Zn(HC₃N₃O₃) has a set of five non-zero SHG tensors that were calculated to be d₁₂ = −7.6815 pm V⁻¹, d₁₃ = −1.652 pm V⁻¹, d₂₅ = −1.153 pm V⁻¹, d₃₆ = 0.12 pm V⁻¹, and d₁₁ = 8.017 pm V⁻¹. The dominant d₁₁ tensor is about 20-fold enhanced over the d₃₆ of KDP. The SHG-weighted electron density analysis focusing on the d₁₁ tensor was conducted to quantify the contributions from each structure building unit (Fig. 6). The SHG weight of the d₁₁ component in the N₂H₄Zn(HC₃N₃O₃) crystal (Fig. 6b and d) demonstrates that the virtual electron and virtual hole states are primarily driven by the (HC₃N₃O₃)²⁻ ring, with Zn²⁺ and [N₂H₄] contributing to a lesser extent.

The unoccupied molecular orbitals are attributed to the (HC₃N₃O₃)²⁻ ring and the nitrogen atoms in the [N₂H₄] molecule. This indicates that the SHG predominantly stems from the (HC₃N₃O₃)²⁻ rings, with non-negligible contributions from the Zn²⁺ and [N₂H₄] molecules, which contribute 79.60%, 10.50%, and 9.90% (Table S10†), respectively. This finding underscores the effective enhancement of the SHG responses in N₂H₄Zn(HC₃N₃O₃) through the synergistic action of multiple chromophores.

Conclusions

In summary, a novel hydro-isocyanurate N₂H₄Zn(HC₃N₃O₃) was discovered. This material exhibits an SHG response that is 13 × KDP, representing the strongest among cyanurates. The unique topological diamond-like framework not only achieves a short absorption edge at 217 nm and a large birefringence of Δn_obv. = 0.294@589 nm, but also facilitates an exceptionally high thermal stability, and strong water resistance. Moreover, such a topological diamond-like framework also displays tunable multicolor room-temperature phosphorescence and a long RTP lifetime of 448 ms, accompanied by a long-lasting afterglow visible to the naked eye for 1.2 s, which is the longest among SHG-based metal–organic complexes, highlighting the material's potential for diverse applications in optoelectronics and beyond.

Data availability

Data available in the ESI† include the experimental section and additional tables and figures.

Author contributions

Can Yang and Yuwei Kang synthesized and characterized the title compound, and completed the writing of this manuscript. Qi Wu and Ling Chen provided experimental ideas and revised the manuscript. Xuefei Wang and Jie Gou participated in the data analysis and discussion of the article. Yi Xiong provided assistance in the characterization of compounds. Zece Zhu provided a discussion of the testing and data analysis of phosphorescence. The manuscript was written through contributions of all authors.

Conflicts of interest

There are no conflicts to declare.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (no. 22275052). The authors would like to thank Chensheng Lin, Jun Zhang, Yuchao Li and Xingxing Jiang for their help in the theoretical calculations.

Notes and references

1. P. Becker, Adv. Mater., 1998, 10, 979–992.
2. D. Cyranoski, Nature, 2009, 457, 953–956.
3. D. F. Eaton, Science, 1991, 253, 281–287.
4. N. Savage, Nat. Photonics, 2007, 1, 83–85.
5. R. Ikuta, Y. Kusaka, T. Kitano, H. Kato, T. Yamamoto, M. Koashi and N. Imoto, Nat. Commun., 2011, 2, 537.
6. C. Wu, T. Wu, X. Jiang, Z. Wang, H. Sha, L. Lin, Z. Lin, Z. Huang, X. Long and M. G. Humphrey, J. Am. Chem. Soc., 2021, 143, 4138–4142.
7. H. Liu, H. Wu, Z. Hu, J. Wang, Y. Wu and H. Yu, J. Am. Chem. Soc., 2023, 145, 12691–12700.
8. Y. Yang, Y. Xiao, B. Li, Y.-G. Chen, P. Guo, B. Zhang and X.-M. Zhang, J. Am. Chem. Soc., 2023, 145, 22577–22583.
9. S. Fang, H. Li, Y. Xie, H. Li, Y. Wang and Y. Shi, Small, 2021, 17, 2103831.
10. Z. Zhu, L. Zeng, W. Li, W. Xu and D. Tian, ACS Sustainable Chem. Eng., 2022, 10, 16752–16759.
11. Z. Qi, B. Zhou and D. Yan, Mater. Chem. Front., 2023, 7, 3475–3493.
12. X. Kang and M. Zhu, Chem. Soc. Rev., 2019, 48, 2422–2457.
13. L. Chen, L. Yu, Y. Liu, H. Xu, W. Li, F. Wang, J. Zhu, K. Yi, L. Ma and H. Xiao, ACS Sens., 2023, 8, 3104–3115.
14. Z. Zhu, L. Zeng, W. Li, D. Tian and W. Xu, ACS Sustainable Chem. Eng., 2021, 9, 17420–17426.
15. S. Xu, R. Chen, C. Zheng and W. Huang, Adv. Mater., 2016, 28, 9920–9940.
16. J. Lu, X. Liu, M. Zhao, X. B. Deng and L. M. Wu, J. Am. Chem. Soc., 2021, 143, 3647–3654.
17. F. Ge, B.-H. Li, P. Cheng, G. Li, Z. Ren, J. Xu and X.-H. Bu, Angew. Chem., Int. Ed., 2022, 61, e202115024.
18. D. Lin, M. Luo, C. Lin, F. Xu and N. Ye, J. Am. Chem. Soc., 2019, 141, 3390–3394.
19. Y. Li, W. Huang, Y. Zhou, X. Song, J. Zheng, H. Wang, Y. Song, M. Li, J. Luo and S. Zhao, Angew. Chem., Int. Ed., 2023, 62, e202215145.
20. L. Liu, Z. Bai, L. Hu, D. Wei, Z. Lin and L. Zhang, J. Mater. Chem. C, 2021, 9, 7452–7457.
21. Y. Liu, Y. P. Gong, S. Geng, M. L. Feng, D. Manidaki, Z. Deng, C. C. Stoumpos, P. Canepa, Z. Xiao and W. X. Zhang, Angew. Chem., Int. Ed., 2022, 61, e202208875.
22. X. Meng, X. Zhang, Q. Liu, Z. Zhou, X. Jiang, Y. Wang, Z. Lin and M. Xia, Angew. Chem., 2023, 135, e202214848.
23. Y. Kang, C. Yang, J. Gou, Y. Zhu, Q. Zhu, W. Xu and Q. Wu, Angew. Chem., 2024, 136, e202402086.
24. K. Wan, B. Tian, Y. Zhai, Y. Liu, H. Wang, S. Liu, S. Li, W. Ye, Z. An and C. Li, Nat. Commun., 2022, 13, 5508.
25. H. Liu, Y. Gao, J. Cao, T. Li, Y. Wen, Y. Ge, L. Zhang, G. Pan, T. Zhou and B. Yang, Mater. Chem. Front., 2018, 2, 1853–1858.
26. J. Yu, H. Ma, W. Huang, Z. Liang, K. Zhou, A. Lv, X.-G. Li and Z. He, JACS Au, 2021, 1, 1694–1699.
27. H. Ma, Q. Peng, Z. An, W. Huang and Z. Shuai, J. Am. Chem. Soc., 2018, 141, 1010–1015.
28. D. Wang, X. Zhang, F. Liang, Z. Hu and Y. Wu, Dalton Trans., 2021, 50, 5617–5623.
29. D. Lin, M. Luo, C. Lin, F. Xu and N. Ye, J. Am. Chem. Soc., 2019, 141, 3390–3394.
30. J. Lu, Y.-K. Lian, L. Xiong, Q.-R. Wu, M. Zhao, K.-X. Shi, L. Chen and L.-M. Wu, J. Am. Chem. Soc., 2019, 141, 16151–16159.
31. N. Wang, F. Liang, Y. Yang, S. Zhang and Z. Lin, Dalton Trans., 2019, 48, 2271–2274.
32. X. Meng, F. Liang, K. Kang, J. Tang, T. Zeng, Z. Lin and M. Xia, Inorg. Chem., 2019, 58, 11289–11293.
33. X. Meng, K. Kang, F. Liang, J. Tang, Z. Lin, W. Yin and M. Xia, Dalton Trans., 2020, 49, 1370–1374.
34. X. Meng, K. Kang, F. Liang, J. Tang, W. Yin, Z. Lin and M. Xia, Inorg. Chem. Front., 2020, 7, 3674–3686.
35. M. Xia, M. Zhou, F. Liang, X. Meng, J. Yao, Z. Lin and R. Li, Inorg. Chem., 2018, 57, 32–36.
36. X. Meng, X. Zhang, Q. Liu, Z. Zhou, X. Jiang, Y. Wang, Z. Lin and M. Xia, Angew. Chem., 2023, 135, e202214848.
37. Y. Song, D. Lin, M. Luo, C. Lin, Q. Chen and N. Ye, Inorg. Chem. Front., 2020, 7, 150–156.
38. Y. Chen, C. Hu, Z. Fang and J. Mao, Inorg. Chem. Front., 2021, 8, 3547–3555.
39. M. Aibibula, L. Wang and S. Huang, ACS Omega, 2019, 4, 22197–22202.
40. X. Meng, F. Liang, J. Tang, K. Kang, Q. Huang, W. Yin, Z. Lin and M. Xia, Eur. J. Inorg. Chem., 2019, 2019, 2791–2795.
41. F.-Y. Cao, H.-H. Liu, Y. Mu, Z.-Z. Xue, J.-H. Li and G.-M. Wang, J. Phys. Chem. Lett., 2022, 13, 6975–6980.
42. Z. Luo, Y. Liu, Y. Liu, C. Li, Y. Li, Q. Li, Y. Wei, L. Zhang, B. Xu and X. Chang, Adv. Mater., 2022, 34, 2200607.
43. H. Liu, W. Ye, Y. Mu, H. Ma, A. Lv, S. Han, H. Shi, J. Li, Z. An and G. Wang, Adv. Mater., 2022, 34, 2107612.
44. D. Li, X. Yang and D. Yan, ACS Appl. Mater. Interfaces, 2018, 10, 34377–34384.
45. Y. J. Ma, X. Fang, G. Xiao and D. Yan, Angew. Chem., Int. Ed., 2022, 61, e202114100.
46. Y. Wang, C. Wang, M. Sun, P. Zhao, X. Fang, J. Zhang, Y. Guo and G. Zhao, Adv. Opt. Mater., 2024, 12, 2301843.
47. H. Zhang, Y. Yan, G. Qiao and J. Li, Inorg. Chem. Commun., 2019, 104, 119–123.
48. S. J. Clark, M. D. Segall, C. J. Pickard, P. J. Hasnip, M. I. Probert, K. Refson, M. C. Payne and Z. Krist, Cryst. Mater., 2005, 220, 567–570.

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Footnotes

† Electronic supplementary information (ESI) available. CCDC 2331157. For ESI and crystallographic data in CIF or other electronic format see DOI: https://doi.org/10.1039/d4sc04476b

‡ These authors contributed equally.

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