A Self-healing Epoxy Composite Coating Based on pH-responsive PCN-222 Smart Containers for Long-term Anticorrosion of Aluminum Alloy
一种基于pH响应PCN-222智能容器的铝合金长期防腐自修复环氧复合涂料

Shucheng Ren ^[a], Fandi Meng^*[a], Xiaoming Li^[b], Yu Cui^[c], Rui Liu ^[a], Yongli Liu ^[b], Xianwei Hu ^[d], Li Liu^*[a] and Fuhui Wang ^[a]
任淑成 ^[a] 、孟凡迪 ^*[a] 、李晓明 ^[b] 、崔宇 ^[c] 、刘瑞 ^[a] 、刘永立 ^[b] 、胡显伟 ^[d] 、刘 ^*[a 丽 ^] 、王 ^[a] 福辉

[a] Shenyang National Laboratory for Materials Science, Northeastern University, Shenyang, 110819, P.R. China.
[a] 东北大学沈阳材料科学国家实验室， 110819沈阳.

[b] Department of Materials Physics and Chemistry, School of Materials Science and Engineering, Northeastern University, Shenyang, Liaoning, 110819, PR China.
[b] 东北大学材料科学与工程学院材料物理与化学系， 110819辽宁沈阳.

[c] Shi-chang xu Innovation Center for Advanced Materials, Institute of Metal Research, Chinese Academy of Sciences, Wencui Road 62, Shenyang 110016, China.
[c] 中国科学院金属研究所徐世昌先进材料创新中心，中国沈阳110016文翠路62号。

[d] School of Metallurgy, Northeastern University, Shenyang 110819, China.
[d] 东北大学冶金学院， 沈阳110819.

* Fandi Meng - Shenyang National Laboratory for Materials Science, Northeastern University, Shenyang, 110819, P.R. China;
* Fandi Meng - 东北大学沈阳材料科学国家实验室，中国沈阳，110819;

Telephone: +15040140891.
电话： +15040140891.

E-mail: fandimeng@mail.neu.edu.cn.
电子邮件：fandimeng@mail.neu.edu.cn。

1. Chemicals and reagents.
1.化学品和试剂。

In our experiment, concentrated hydrochloric acid (GR), xylene (AR) and normal butanol (AR) were purchased by Sinopharm Chemical Reagent Co., Ltd., China. Other analytical (AR) reagents were purchased from Aladdin Reagent Co., Ltd., China. including N, N′-dimethylformamide (DMF), ZrCl₄, dichloroacetic acid, and ethanol. The tetrakis (4-carboxyphenyl) porphyrin (TCPP-H₂) was purchased from Shanghai kylpharm Co., Ltd. Epoxy resin (E44) and polyamide curing agent (650, amine value 220-240 KOH/g) were provided by Shanghai Macklin Biochemical Co., Ltd. The 5083 Al alloy was purchased from Shanghai Saimun Metal Material Co., Ltd, China, and its main chemical composition is Al (bal), Mg (4 wt.%), Mn (0.4-1 wt.%), Fe (0.4 wt.%), Si (0.4 wt.%), Cr (0.25 wt.%), Zn (0.25 wt.%), Ti (0.15 wt.%), and other elements (< 0.15 wt.%).
在我们的实验中，浓盐酸（GR）、二甲苯（AR）和正丁醇（AR）由中国国药集团化学试剂有限公司购买。其他分析（AR）试剂购自中国阿拉丁试剂有限公司。包括N，N′-二甲基甲酰胺（DMF）、ZrCl ₄ 、二氯乙酸和乙醇。四（4-羧基苯基）卟啉（TCPP-H ₂ ）购自上海凯普药业有限公司，环氧树脂（E44）和聚酰胺固化剂（650，胺值220-240 KOH/g）由上海麦克林生化有限公司提供。5083铝合金购自中国上海赛门金属材料有限公司，其主要化学成分为Al（bal）、Mg（4重量%）、Mn（0.4-1重量%）、Fe（0.4重量%）、Si（0.4重量%）、Cr（0.25重量%）、Zn（0.25重量%）、Ti（0.15重量%）和其他元素（<0.15重量%）。

5083 Al alloy with an exposed area of 25 cm² was grounded to 800# grit size using SiC papers and degreased with acetone and ethanol.
将暴露面积为25厘米 ² 的5083铝合金用碳化硅纸磨成800#粒度，并用丙酮和乙醇脱脂。

2. Preparation of PCN-222.
2.PCN-222的制备。

The PCN-222 sample was synthesized with slight modifications based on recent reports.[1] Typically, ZrCl₄ (650 mg) and TCPP-H₂ (130 mg) were dissolved in 160 mL of DMF and 5 mL of dichloroacetic acid, then stirred at 130 °C for 24 h in the 500 mL round-bottomed flask. The obtained mixture was separated by centrifugation and repeatedly washed with DMF and acetone, then dried overnight at 60 °C. Next, PCN-222 was activated with hydrochloric acid (HCl). The obtained PCN-222 powder was dispersed in the mixed solution of 50 mL DMF and 5 mL HCl (3 M), then stirred and refluxed at 130 °C for 24 hours. After centrifugation, the solid was washed with DMF and ethanol several times and dried at 90 °C overnight.
PCN-222样品是根据最近的报告进行轻微修改后合成的。[1] 通常，将 ZrCl ₄ （650 mg） 和 TCPP-H ₂ （130 mg） 溶解在 160 mL DMF 和 5 mL 二氯乙酸中，然后在 130 °C 下在 500 mL 圆底烧瓶中搅拌 24 小时。将所得混合物离心分离，并用DMF和丙酮反复洗涤，然后在60°C下干燥过夜。 接下来，用盐酸（HCl）活化PCN-222。将所得的PCN-222粉末分散在50 mL DMF和5 mL HCl（3 M）的混合溶液中，然后在130°C下搅拌回流24小时。离心后，将固体用DMF和乙醇洗涤数次，并在90°C下干燥过夜。

3. Preparation of 8-HQ@PCN-222.
3. 准备 8-HQ@PCN-222。

The 200 mg powders of activated PCN-222 were dispersed in 50 mL of ethanol solution containing 8-HQ (0.27 M). The suspension was stirred for 12 h under negative pressure in a vacuum reaction flask, in which the air in the flask was pumped every 2 h to maintain the negative pressure as much as possible. The solid was collected by centrifugation, washed three times with ethanol and deionized water, and finally obtained by freeze-drying.
将 200 mg 活化的 PCN-222 粉末分散在含有 8-HQ （0.27 M） 的 50 mL 乙醇溶液中。悬浮液在真空反应瓶中负压搅拌12小时，其中每2小时泵送一次烧瓶中的空气，以尽可能保持负压。将固体离心收集，用乙醇和去离子水洗涤三次，最后冷冻干燥制得。

4. Preparation of epoxy composite coating with 8-HQ@PCN-222.
4.用8-HQ@PCN-222制备环氧复合涂料。

Various epoxy composite coatings were prepared according to the typical procedure. Specifically, 3 g of epoxy resin was stirred for 30 min in the solution of 1.05 g of butyl alcohol and xylene (m₁:m₂ = 3:7) to ensure its complete dissolution. Then, 30 mg of 8-HQ@PCN-222 powder was added to the mixed solution and stirred for 2 h under sealing condition. Then, 2.4 g of polyamide curing agent was added, and the coating was cured by slow stirring for 20 min. The epoxy mixture was applied to the pre-treated 5083 Al alloy after ultrasonic de-airing, and cured in an oven at the following conditions: 40 °C for 4 h, 60 °C for 20 h, and room temperature for 7 days. Finally, the epoxy coating containing 1 wt.% 8-HQ@PCN-222 (by weight of epoxy resin) was obtained, called 8-HQ@PCN-222-1% coating. In addition, other epoxy composite coatings were prepared according to a similar procedure, except that the content of 8-HQ@PCN-222 was changed to 0 wt.%, 0.5 wt.%, and 3 wt.%, which were referred to the pure epoxy coating, 8-HQ@PCN-222-0.5% coating, and 8-HQ@PCN-222-3% coating, respectively. The thickness of all coatings was controlled to 100 ± 20 μm.
根据典型程序制备了各种环氧复合涂料。具体地，将3克环氧树脂在1.05克丁醇和二甲苯（m ₁ ：m ₂ =3：7）的溶液中搅拌30分钟，以确保其完全溶解。然后，将30 mg的8-HQ@PCN-222粉末加入混合溶液中，并在密封条件下搅拌2 h。然后加入聚酰胺固化剂2.4 g，缓慢搅拌20 min固化涂层。将环氧混合物涂在超声除气后预处理的5083铝合金上，并在以下条件下在烘箱中固化：40°C4 h，60 °C20 h，室温7 d。最后，得到含有1重量%的8-HQ@PCN-222（按环氧树脂重量计）的环氧涂层，称为8-HQ@PCN-222-1%涂层。此外，其他环氧复合涂料也按照类似的程序制备，只是8-HQ@PCN-222的含量分别为0重量%、0.5重量%和3重量%，分别称为纯环氧涂层、8-HQ@PCN-222-0.5%涂层和8-HQ@PCN-222-3%涂层。所有涂层的厚度控制在100±20μm。

The scratched coating was prepared based on the intact coating with 100 µm thickness. The scratch was prepared by a CNC machining milling machine (M5A850), programmed to produce scratches 0.2 mm wide and 10 µm deep each time, and the procedure was repeated 10-11 times to ensure that the coating was scratched through without damaging the substrate as much as possible.
基于厚度为100 μm的完整涂层制备划痕涂层。划痕由CNC加工铣床（M5A850）制备，每次编程为产生0.2毫米宽，10μm深的划痕，并重复该过程10-11次，以确保涂层被划穿，而不会尽可能损坏基材。

5. Characterization methods.
5.表征方法。

5.1 Powder sample characterization
5.1 粉末样品表征

In this work, we performed a series of characterizations on the powder samples PCN-222 and 8-HQ@PCN-222. The morphology of the samples was characterized by scanning electron microscopy (SEM, JEOL, SU-8000, and S4800) operating with 5 kV and 2 kV at 25 °C (room temperature). Transmission electron microscopy (TEM) and corresponding energy-dispersive X-ray spectroscopy (EDS) elemental mapping were performed on a JEM-2100F electron microscope operating with 200 kV at room temperature. The crystalline structure was examined by X-ray diffraction (XRD), using a Rigaku corporation SmartLab and diffractometer with Cu Kα radiation (λ = 0.154 nm). Fourier infrared spectroscopy (FT-IR) is used to obtain the chemical structure of the samples, adopting a Thermo Scientific Nicolet iS20 with a spectral region of 400-4000 cm^-1. The surface area and the porosity distribution of the as-prepared materials were calculated by the Brunauer-Emmett-Teller (BET) equation and the Barrett-Joyner-Halenda (BJH) equation, respectively (TriStar II 3020).
在这项工作中，我们对粉末样品 PCN-222 和 8-HQ@PCN-222 进行了一系列表征。通过扫描电子显微镜（SEM、JEOL、SU-8000和S4800）在25 °C（室温）下以5 kV和2 kV工作对样品的形貌进行了表征。透射电子显微镜（TEM）和相应的能量色散X射线光谱（EDS）元素映射在室温下以200 kV工作的JEM-2100F电子显微镜进行。通过X射线衍射（XRD）检查晶体结构，使用理学公司的SmartLab和具有Cu Kα辐射（λ = 0.154nm）的衍射仪。采用光谱区域为400-4000 cm ^-1 的Thermo Scientific Nicolet iS20，采用傅里叶红外光谱（FT-IR）获得样品的化学结构，分别采用Brunauer-Emmett-Teller（BET）方程和Barrett-Joyner-Halenda（BJH）方程计算了制备材料的表面积和孔隙率分布（TriStar II 3020）。

5.2. The release experiment of 8-HQ
5.2. 8-HQ的发布实验

The release experiment of 8-HQ was performed in 3.5 wt.% NaCl solution with different pH environments (pH = 3, 7, and 11). A 100 mg portion of 8-HQ@PCN-222 sample was added into 1000 mL of 3.5 wt.% NaCl solution and stirred rapidly to obtain a uniform suspension at room temperature. Then, approximately 2 mL of the suspension was removed at a given time and filtered through a 0.45 μm microporous membrane filter. The residual solutions were characterized by UV-VIS spectroscopy to confirm the concentration of 8-HQ at different intervals for 12 h. Standard concentration-absorbance equations of 8-HQ are established as the following[2]:
在不同pH环境（pH=3、7和11）的3.5 wt.% NaCl溶液中进行8-HQ的释放实验。将 100 mg 份量的 8-HQ@PCN-222 样品加入 1000 mL 3.5 wt.% NaCl 溶液中，并在室温下快速搅拌以获得均匀的悬浮液。然后，在给定时间除去约 2 mL 悬浮液，并通过 0.45 μm 微孔膜过滤器过滤。采用紫外-可见分光光度计对残余溶液进行表征，确认8-HQ在不同时间间隔内的浓度持续12 h。8-HQ的标准浓度-吸光度方程建立如下[2]：

(pH = 3) (S1)
（pH = 3）（小一）

(pH = 7) (S2)
（pH = 7）（小二）

(pH = 11) (S3)
（pH = 11）（小三）

where x indicates the solution concentration and y represents the UV absorbance intensity. The release of 8-HQ from 8-HQ@PCN-222 is calculated according to these equations.
其中 x 表示溶液浓度，y 表示紫外吸光度强度。根据这些公式计算8-HQ@PCN-222释放8-HQ。

5.3. The electrochemical impedance spectroscopy (EIS) test
5.3. 电化学阻抗谱（EIS）测试

The EIS tests of intact and scratched coatings were performed in 3.5 wt.% NaCl solution using an electrochemical workstation (PARSTAT 4000 A). For intact coatings, the traditional three-electrode system was used, in which a platinum sheet, a saturated calomel electrode, and a coated 5083Al alloy with an exposed area of 10 cm² were used as an auxiliary, reference, and working electrodes, respectively. For the scratched coatings, only the working electrodes were changed to samples with 0.5 cm artificial scratches. The working electrode was held at its open circuit potential (OCP) for 1200 s prior to the measurement to ensure that the OCP reached a steady state. EIS tests were performed over a frequency range of 0.01 Hz to 10⁵ Hz with alternating current signal amplitudes of 50 mV for intact coatings and 10 mV for scratched coatings, and all EIS data were fitted by the ZsimpWin software.
使用电化学工作站（PARSTAT 4000 A）在3.5 wt.%NaCl溶液中对完整和划痕涂层进行EIS测试。对于完整的涂层，使用传统的三电极系统，其中铂片、饱和甘汞电极和暴露面积为 10 cm ² 的涂层 5083Al 合金分别用作辅助电极、参比电极和工作电极。对于划痕涂层，仅将工作电极更改为具有0.5厘米人工划痕的样品。在测量之前，将工作电极保持在开路电位 （OCP） 下 1200 秒，以确保 OCP 达到稳定状态。EIS测试在0.01 Hz至10 ⁵ Hz的频率范围内进行，完整涂层的交流信号幅度为50 mV，划痕涂层的交流信号幅度为10 mV，所有EIS数据均由ZsimpWin软件拟合。

5.4. The neutral salt spray (NSS) test
5.4. 中性盐雾（NSS）测试

The NSS test was performed in a salt spray chamber at 30 °C in accordance with GB/T1771-91.[3] All coatings with artificial defects were exposed to a 5 wt.% NaCl neutral salt spray environment. Digital photographs of the scratches were taken after 25 days and 50 days, and the corrosion at the scratch area was further observed under a stereomicroscope after 50 days.
NSS试验按照GB/T1771-91标准在30°C盐雾室中进行。[3] 所有具有人工缺陷的涂层都暴露在 5 wt.% NaCl 中性盐雾环境中。在25天和50天后拍摄划痕的数码照片，并在50天后在立体显微镜下进一步观察划痕区域的腐蚀。

5.5. The scanning vibrating electrode technique (SVET) test
5.5. 扫描振动电极技术（SVET）测试

The SVET measurements were performed on the pure epoxy coating and 8-HQ@PCN-222-1% coatings based on a system from Applicable Electronics Inc. (USA). Prior to testing, an artificial defect was created on the surface of cubic samples (1×1×1 cm) with a size of about 3 mm in length and 0.1 mm in width. The prepared samples were immersed in 3.5 wt.% NaCl solution for 36 h, and the current densities were detected at 100 μm above their surface. The sample area was scanned every 1.5 h with an amplitude of 20 μm using the vibrating Pt-blackened electrode tip (20 μm diameter). All data were analyzed using Quikgrid software. The anodic zone is associated with the formation of metal cations in the anodic reaction, while the cathodic zone reflects the cathodic reaction.
SVET测量是在纯环氧树脂涂层和8-HQ@PCN-222-1%涂层上进行的，该涂层基于Applicable Electronics Inc.（美国）的系统。在测试之前，在长约3毫米、宽约0.1毫米的立方体样品（1×1×1厘米）表面产生人为缺陷。将制备的样品浸入3.5 wt.%NaCl溶液中36 h，并在其表面以上100 μm处检测电流密度。使用振动的 Pt 发黑电极尖端（直径 20 μm）每 1.5 小时扫描一次样品区域，振幅为 20 μm。所有数据均使用Quikgrid软件进行分析。阳极区与阳极反应中金属阳离子的形成有关，而阴极区则反映了阴极反应。

6. Computational methods.
6.计算方法。

To further determine the binding modes between the 8-HQ and PCN-222 in an ethanol solution, density functional theory (DFT) calculations were performed. This work focused mainly on the interactions of 8-HQ with porphyrin and Zr₆ clusters of PCN-222.
为了进一步确定8-HQ和PCN-222在乙醇溶液中的结合模式，进行了密度泛函理论（DFT）计算。本研究主要关注8-HQ与PCN-222卟啉和Zr ₆ 簇的相互作用。

6.1. Conformational search
6.1. 构象搜索

The Zr₆-based nodes of PCN-222 adopted the type of a staggered mixed proton topology to match experimental results, namely [Zr₆(m₃-O)₄(m₃-OH)₄(OH)₄(H₂O)₄]⁸⁺, which was demonstrated by C. J. Cramer by IR spectroscopy and structurally elucidated in their DFT study.[4] In each cluster, four of the six Zr atoms were assigned to a water molecule and a terminal hydroxyl group and formed intramolecular hydrogen bonds, creating the most stable configuration. Moreover, eight benzoate groups (PhCOO^–) were introduced to maintain an overall neutral charge, and their distribution and orientation remained consistent with PCN-222. Then, the positions of all H atoms were further refined by performing constrained geometry optimizations, while all other atoms were fixed. Finally, Zr₆-based nodes and carboxyl groups were allowed to relax in the presence of the fixed linker fragments. The obtained configurations are shown in Figure. S6a.
PCN-222的Zr ₆ 基节点采用交错混合质子拓扑类型来匹配实验结果，即[Zr ₆ （m ₃ -O） ₄ （m ₃ -OH） ₄ （OH） ₄ （H ₂ O） ₄ ] ⁸⁺ ，C. J. Cramer通过红外光谱证明了这一点，并在DFT研究中进行了结构阐明。[4] 在每个团簇中，六个 Zr 原子中的四个被分配到一个水分子和一个末端羟基，并形成分子内氢键，从而形成最稳定的构型。此外，引入了8个苯甲酸酯基团（PhCOO ^– ）以保持整体中性电荷，其分布和取向与PCN-222保持一致。然后，通过执行约束几何优化进一步细化所有H原子的位置，而所有其他原子都是固定的。最后，允许基于Zr ₆ 的节点和羧基在固定连接子片段存在下松弛。得到的配置如图所示。S6a。

The initial structure of 8-HQ and porphyrin was obtained by Chemdraw software. The obtained configuration after structure optimization is shown in Figures. S6b and 6c, respectively.
8-HQ和卟啉的初始结构由Chemdraw软件获得。结构优化后得到的配置如图所示。分别为 S6b 和 6c。

6.2. DFT calculation
6.2. DFT计算

All DFT calculations were performed with the PBE0 density of the Gaussian 09 software package.[5, 6] The geometry optimization was carried out at the PBE0-D3 (BJ)/def2SVP level.[7-9] Meanwhile, the continuum solvation model PCM was performed.[10, 11] Moreover, the spin multiplicity of Zr₆ clusters was fully considered. The PBE0-D3(BJ))/def2-TZVPD level was used in the single-point calculation,[12-17] and the SMD model was applied for the solvation with ethanol.[18] The def2-TZVPD obtained from the basis set exchange python library could automatically endow the full electronic basis set for the pseudo-potential basis set for Zr. The binding energy (BE) values could describe the binding stability of different fragments in a compound. Thus, BE with energy correction is calculated to evaluate binding affinities, and the formulas are as follows [19]:
所有DFT计算均使用Gaussian 09软件包的PBE0密度进行。[5, 6]几何优化在PBE0-D3（BJ）/def2SVP级别进行。[7-9] 同时，进行了连续介质溶剂化模型 PCM。[10, 11]此外，还充分考虑了Zr ₆ 团簇的自旋多重性。单点计算采用PBE0-D3（BJ））/def2-TZVPD水平[12-17]，并采用SMD模型进行乙醇溶剂化反应。[18] 从基集交换 python 库获得的 def2-TZVPD 可以自动为 Zr 的伪势基集提供完整的电子基集。结合能（BE）值可以描述化合物中不同片段的结合稳定性。因此，计算具有能量校正的BE来评估结合亲和力，其公式如下[19]：

E_(Zr-quin) = EIC_{(Zr-quinoline)} – E_(Zr) – E_(quin) + E_(correction) (S4)
E _(Zr-quin) = EIC _{(Zr-quinoline)} – E _(Zr) – E _(quin) + E _(correction) （S4）

E_(porph-quin) = EIC_(porph-quin) – E_(porph) – E_(quin) + E_(correction) (S5)
E _(porph-quin) = EIC _(porph-quin) – E _(porph) – E _(quin) + E _(correction) （S5）

where EIC refers to the energy of the interacting complex; E_(Zr), E_(quin), and E_(porph) represent the energy of the Zr₆ cluster, 8-HQ and porphyrin, respectively.
其中EIC是指相互作用的复合物的能量;E _(Zr) 、E _(quin) 和E _(porph) 分别代表Zr ₆ 团簇、8-HQ和卟啉的能量。

In addition, the independent gradient model based on Hirshfeld partition (IGMH) was used to intuitively analyze the interaction mode between different fragments.[20] All isosurface maps were rendered by the VMD 1.9.3 program based on the output of Multiwfn 3.8.[21, 22]
此外，利用基于Hirshfeld分区（IGMH）的独立梯度模型直观地分析了不同片段之间的交互模式。[20] 所有等值面图均由 VMD 1.9.3 程序根据 Multiwfn 3.8 的输出绘制。[21, 22]

7. Characterization results.
7.表征结果。

Figure. S1. Structure map of 8-HQ@PCN-222, consisting of 8-HQ, TCPP-H₂ linker and Zr-based unit.
数字。S1 中。8-HQ@PCN-222的结构图，由8-HQ、TCPP-H ₂ 连接物和Zr基单元组成。

Figure. S2. SEM top images of (a) pure epoxy coating, (b) 8-HQ@PCN-222-0.5% coating, (c) 8-HQ@PCN-222-1% coating, and (d) 8-HQ@PCN-222-3% coating.
数字。S2 中。（a）纯环氧涂层，（b）8-HQ@PCN-222-0.5%涂层，（c）8-HQ@PCN-222-1%涂层和（d）8-HQ@PCN-222-3%涂层的SEM顶部图像。

Figure. S3. Schematic mechanism of the reaction of porphyrin in the PCN-222 with epoxy groups. The covalent reaction of (a) tertiary amine，(b) secondary amine with epoxy groups.
数字。S3 中。PCN-222中卟啉与环氧基团反应机理示意图。（a）叔胺，（b）仲胺与环氧基团的共价反应。

8. Results of EIS tests.
8. EIS测试结果。

Figure. S4. The equivalent electric circuit models of (a)R(QR) and (b) R(Q(R(QR))) are employed to fit the impedance data in 3.5 wt.% NaCl solution at different immersion time.
数字。S4 中。采用（a）R（QR）和（b）R（Q（R（QR）））等效电路模型，拟合3.5 wt.% NaCl溶液中不同浸泡时间的阻抗数据。

The equivalent electrical circuit model of R(QR) is used to fit the impedance data of 8-HQ@PCN-222-1% coating at the initial stage of immersion (Figure. S4a). Meanwhile, the other impedance data are fitted by the equivalent electrical circuit model in Figure. S4b. The above equivalent electrical circuits involve solution resistance (R_s), coating resistance (R_c), charge transfer resistance (R_ct), coating constant phase element (CPE_c), and double layer constant phase element (CPE_dl).
使用R（QR）的等效电路模型拟合8-HQ@PCN-222-1%涂层在浸入初始阶段的阻抗数据（图1）。S4a）。同时，其他阻抗数据由图中的等效电路模型拟合。S4b的。上述等效电路包括溶液电阻（R _s ）、涂层电阻（R _c ）、电荷转移电阻（R _ct ）、涂层恒相元件（CPE _c ）和双层恒相元件（CPE _dl ）。

A constant phase element (CPE) is used instead of a capacitor due to the deviation from the ideal capacitance behavior, and it was evaluated based on Brug’s formula[23, 24]:
由于偏离理想电容行为，使用恒相元件（CPE）代替电容器，并根据Brug公式[23,24]进行评估：

(S6)
（中六）

(S7)
（S7）

Where Z is the impedance; Y₀ refers to the admittance; j² = −1 is the imaginary unit; ω represents the angular frequency (rad s⁻¹); n is the CPE exponent (0 < n ≤ 1); represents the effective capacitance; and R_e represents resistance (either R_c or R_ct).
其中 Z 是阻抗;Y ₀ 是指准入;j ² = −1 是虚数单位;ω 表示角频率 （rad s ⁻¹ ）;n 是 CPE 指数 （0 < n ≤ 1）;表示有效电容;R _e 表示电阻（R _c 或 R _ct ）。

Figure. S5. The equivalent electrical circuits model of (a) R(Q(R(QR))), (b) R(Q(R(QR)(QR))) are applied to fit impedance data of the different scratched coatings in 3.5 wt.% NaCl solution.
数字。S5.应用（a） R（Q（R（QR）））、（b） R（Q（R（QR）（QR）））的等效电路模型来拟合3.5 wt.% NaCl溶液中不同划痕涂层的阻抗数据。

The equivalent electrical circuit of R(Q(R(QR))) is selected to analyze the scratched pure epoxy coating and the initial immersion stage of scratched coatings with fillers (Figure. S5a). Meanwhile, the other impedance data are fitted by the equivalent electrical circuit of R(Q(R(QR)(QR))) (Figure. S5b).[2] In the above equivalent electrical circuits, R_s is the solution resistance; R_c and CPE_c represent the resistance and constant phase element of the coating, respectively; R_ct and CPE_dl is the charge transfer resistance, and electric double layer constant phase element, respectively; R_film and CPE_film represent the resistance and constant phase element of inhibitor film forming on the exposed Al substrate, respectively. A constant phase element (CPE) is used instead of the capacitor in all fittings due to the deviation from the ideal capacitance.
选取R（Q（R（QR）））的等效电路，分析划痕纯环氧涂层和填料划痕涂层的初始浸泡阶段（图1）。S5a）。同时，其他阻抗数据由等效电路 R（Q（R（QR）（QR））） 拟合 （图.S5b）。[2] 在上述等效电路中，R _s 是溶液电阻;R _c 和 CPE _c 分别表示涂层的电阻和恒定相位元件;R _ct 和CPE _dl 分别为电荷转移电阻和双电层恒相元件;R _film 和CPE _film 分别表示在暴露的Al衬底上形成的抑制剂薄膜的电阻和恒定相位元件。由于偏离理想电容，所有配件都使用恒定相位元件 （CPE） 代替电容器。

Table S1. The parameters obtained by fitting the EIS data of four intact coatings.
表 S1.通过拟合四种完整涂层的EIS数据获得的参数。

Table S2. The parameters obtained by fitting the EIS data of four scratched coatings.
表 S2.通过拟合四块划痕涂层的EIS数据获得的参数。

9. Computational results.
9. 计算结果。

Figure. S6. The optimized geometries of (a) Zr₆ cluster, (b) 8-HQ, and (c) porphyrin. The geometry optimization is carried out at the PBE0-D3 (BJ) /def2SVP level.
数字。S6 中。（a）Zr ₆ 团簇、（b）8-HQ和（c）卟啉的优化几何形状。几何优化在 PBE0-D3 （BJ） /def2SVP 级别进行。

Figure. S7. The initial geometries for the coordination of 8-HQ to porphyrin and Zr₆ in PCN-222.
数字。S7.PCN-222中8-HQ与卟啉和Zr ₆ 配位的初始几何形状。

Figure. S8. Optimized geometries of 8-HQ coordinated to (a) porphyrin, and (b-c) Zr₆ cluster. The N, Zr, C, H, and O atoms are represented by dark blue, gray, blue, white, and red spheres, respectively. Geometry optimization is carried out at the PBE0-D3 (BJ)/def2SVP level.
数字。S8 中。优化的 8-HQ 几何形状与 （a） 卟啉和 （b-c） Zr ₆ 簇配位。N、Zr、C、H 和 O 原子分别用深蓝色、灰色、蓝色、白色和红色球体表示。几何优化在 PBE0-D3 （BJ）/def2SVP 级别进行。

To study the interaction between 8-HQ and porphyrin, the π cloud and hydrogen bonding are considered as binding modes between the two (Figure S7a and S7b). After the geometry optimization, the result indicates that π cloud is the only binding mode between 8-HQ and porphyrin, which is attributed to the strong conjugated ability provided by the large electron-rich aromatic ring in porphyrin. The final optimized geometry, namely Model I, is shown in Figure. S8a. In addition, three binding modes are used to study the interaction of 8-HQ with Zr₆ clusters, which are proposed based on the sites of Zr₆ clusters that could form hydrogen bonds and π interactions with 8-HQ, such as the -OH, -H₂O, -μ₃-OH and benzoate groups (Figure S7c-7d). The optimized geometries are shown in Figures. S8 b-d, which are referred to as Model II, III and IV, respectively. The three models use different types of hydroxyl sites in the Zr₆ cluster to form hydrogen bonds with 8-HQ, where Model II corresponds to the -μ₃-OH and -H₂O groups in the Zr₆ cluster, Model III to the -μ₃-OH and -OH groups, and Model IV to the -OH and -H₂O groups.
为了研究8-HQ和卟啉之间的相互作用，π云和氢键被认为是两者之间的结合模式（图S7a和S7b）。经过几何优化，结果表明π云是8-HQ与卟啉之间唯一的结合模式，这归因于卟啉中大的富电子芳环提供了强大的共轭能力。最终优化的几何形状，即模型 I，如图所示。S8a的。此外，还利用3种结合模式研究了8-HQ与Zr ₆ 团簇的相互作用，基于Zr ₆ 团簇的位点可以形成氢键，并与8-HQ π相互作用，如-OH、-H ₂ O、- ₃ μ-OH和苯甲酸酯基团（图S7c-7d）。优化后的几何形状如图所示。S8 b-d，分别称为II型、III型和IV型。这三种模型使用Zr ₆ 团簇中不同类型的羟基位点与8-HQ形成氢键，其中模型II对应于Zr ₆ 团簇中的- ₃ μ-OH和-H ₂ O基团，模型III对应于- ₃ μ-OH和-OH基团，模型IV对应于-OH和-H ₂ O基团。

Table S3. The energy results obtained from single-point calculations.
表 S3.从单点计算中获得的能量结果。

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