Design of Nacre-Inspired 2D-MoS₂ Nanosheets Assembled with Mesoporous Covalent Organic Frameworks (COFs) for Smart Coatings

Abstract

High loading capacity and smart release of inhibitors are the first and foremost characteristics of nanocontainers, which play a pivotal role in metal active corrosion protection. The present work explores the development of novel protective nanocontainers based on recently emerged covalent organic frameworks (COFs). These highly porous frameworks with large surface area, outstanding thermomechanical properties, low density, and ease of functionalization are used as nanocontainers. On the other hand, molybdenum disulfide (MoS2), a state-of-the-art 2D layered compound with a sheetlike structure, was utilized thanks to its excellent barrier properties. However, these lamellar structures suffer a high agglomeration tendency in polymeric matrices. Therefore, we developed a novel hybrid nanocontainer, inspired by natural nacre, by an in situ growth of COF on MoS2 to improve the stability and provide a high inhibitor loading capacity. The porous and nitrogen-rich structure of COF made it a good carrier to adsorb europium cations as inorganic inhibitors and release them on demand by pH changes to suppress the electrochemical reactions. The as-synthesized nanoplatforms were used as pH-responsive fillers in the epoxy resin. The nanocomposite coatings showed almost 50 kΩ cm2 total resistance and high impedance values (1011 Ω cm2) even after 77 days of immersion. Moreover, salt spray analysis depicted the smallest amount of rust and corrosion product after 31 days in the filled nanocomposite coating. Cathodic delamination and pull-off outcomes denoted that the filled coatings with the as-synthesized nanofiller showed the smallest cathodic delamination radius (3.41 mm) and lowest adhesion loss (24%) compared to the neat epoxy (7.55 mm and 46.7%). As such, the highly porous modified MoS2 nanosheets are considered promising alternatives in a wide range of applications with anticorrosion properties.

Eco-Friendly Fumed Nanosilica@Nanodiamond Hybrid Nanoparticles with Dual Sustainable Self-Healing and Barrier Anticorrosive Performances in Epoxy Coating

“…The more negative the OCP values are, the more diffusion of corrosion agents there is in the coating. 48 The OCP values of the EP/FSiO 2 coating after 10 weeks of immersion are greatly reduced, indicating the penetration of electrolytes into the coating, consistent with the other EIS data presented above. For the EP/FSiO 2 @sND coating, the OCP values always have the highest value at all immersion times among the coatings, which indicates the high protection of the coating against the penetration of corrosive ions from 3.5% NaCl solution to the substrate/coating interface.…”

“…Figure j shows the OCP values versus immersion times. The more negative the OCP values are, the more diffusion of corrosion agents there is in the coating . The OCP values of the EP/FSiO 2 coating after 10 weeks of immersion are greatly reduced, indicating the penetration of electrolytes into the coating, consistent with the other EIS data presented above.…”

“…According to Figure , APTES improves compatibility between the epoxy coating and hybrid nanoparticles by creating interactions between its free amine and silanol groups and the epoxide groups of resin through a ring-opening mechanism (increasing cross-link density), leading to a denser epoxy matrix. Meanwhile, free silanol and amine groups of APTES increase the adhesion of the coating to the MS by creating bonds with the OH groups of MS. ,,, Moreover, FSiO 2 can enhance the adhesion of the coating to the MS substrate . Furthermore, the presence of ND in the nanohybrid structure makes the coating hydrophobic, and its carboxylate groups on the surface can get involved in the epoxy curing reaction by opening epoxide groups (see Figure ), resulting in a higher cross-link density of the epoxy matrix (Figure ).…”

Engineering Active-Site-Induced Homogeneous Growth of Polydopamine Nanocontainers on Loading-Enhanced Ultrathin Graphene for Smart Self-Healing Anticorrosion Coatings

“…The changes in both Tafel’s anodic and cathodic slopes represent the mixed corrosion inhibition by PDA and BTA in UG-BP, which can be adsorbed on electrodes to delay the corrosion process. Besides, the anodic Tafel slope has been greatly increased, indicating that anodic protection predominantly controls the metal corrosion. − It means that the adsorption of inhibitor in the anodic region has been more effective compared to that in the cathodic areas, as reported in previous studies . The corresponding inhibition efficiencies of UG-BP and RG-BP are calculated as 66.02 and 45.10%.…”

High-Performance Trimethylamine Sensor Based on an Imine Covalent Organic Framework

“…33,34 Another peak between 23 and 25°, representing the (002) crystal plane, illustrates the amorphous character of the synthesized COF. 35 Additionally, to better understand the bond formation and local bonding modes of the three materials, we used FTIR spectroscopy to examine the functional groups contained in the materials. Figure 3b clearly shows the presence of imine C�N and C−C�N−C stretching bands at 1617 and 1279 cm −1 , respectively, and the above peaks prove the successful synthesis of imine COFs.…”