Metal organic frameworks (MOFs) as multifunctional nanoplatform for anticorrosion surfaces and coatings

A Phosphate-Modified Aqueous Acrylic-Alkyd Resin for Protective Technology to Prevent Corrosion of Iron Substrates

Iron corrosion is very common in our daily life, and its effective protection can extend its service life. As a small molecule monomer, 2-hydroxyethyl methacrylate phosphate (HEMAP) has a phosphate group that can effectively chelate with iron ions to form a passivation layer (iron phosphate), thus slowing down the corrosion rate of iron. This study synthesized HEMAP-modified acrylic-alkyd resin copolymers with variable concentrations using free radical polymerization. The addition of HEMAP not only increases the cross-linking density of the resin, but it also further strengthens the adhesion between the resins and the iron substrate, which prevents corrosive substances from penetrating the resin. According to electrochemical studies, adding 2% mass fraction of HEMAP to the resin could greatly increase its resistance to corrosion. This study reveals HEMAP's capacity to enhance the protection of coatings on iron substrates and lengthen the metal's service life.

Extraction of lignin from lignocellulosic biomass (bagasse) as a green corrosion inhibitor and its potential application of composite metal framework organics in the field of metal corrosion protection

With increasing awareness of environmental protection, additional attention has been given to environmentally friendly metal anticorrosion research. In this paper, the green organic corrosion inhibitor sodium lignosulfonate (SLS) was extracted from bagasse waste, and a Ce-MOF@SLS smart anticorrosive film containing the inhibitor was prepared on the surface of an aluminum alloy by in situ electrodeposition. The material was characterized by SEM, EDS, FT-IR, XRD and XPS, and its corrosion resistance was tested with EIS and neutral salt spray tests. The electrochemical data showed that the Ce-MOF@SLS film reached a corrosion current density of 3.36 × 10-8 A/cm2, and no corrosion spots appeared after 105 days of salt spray experiments, indicating that the smart film provided long-lasting protection for aluminum alloys. The antiseptic mechanism of the Ce-MOF@SLS smart film was verified by quantum chemical calculations and molecular dynamics simulations. The research result not only provide a new method for the study of green intelligent anti-corrosion films for aluminum alloys, but also offer a novel approach to the treatment of domestic waste.

TiO2-Modified Graphene Oxide Fillers Strengthen Acrylic Coated Samples Corrosion and Weathering Resistance on Q235 Steel

As an exceptional 2D nanofiller, graphene oxide (GO) is extensively employed to amplify the protective properties of coatings. The dispersion of GO significantly influences the protective efficacy of the coatings. Here, a surface modification of GO through the integration of nanosized titanium dioxide (TiO2) was employed, thereby facilitating the synthesis of an FGO-TiO2 nanoparticle characterized by a substantial interlayer spacing (0.91 nm). Subsequently, FGO-TiO2 nanofiller was incorporated into an acrylic coating matrix, resulting in an advanced acrylic coated sample that simultaneously exhibits both corrosion resistance and UV protection properties. EIS analysis revealed that, after 350 h of immersion, the low-frequency impedance modulus of the FGO-TiO2/acrylic coated sample reached 1.028 GΩ·cm2, a significant increase compared to the pure acrylic coated sample (0.017 GΩ·cm2). This improvement suggests the enhanced dispersion of FGO-TiO2 in the acrylic coating, which effectively lengthens the diffusion path for corrosive agents, and it is anticipated to replace the conventional primer-topcoat composite coating system.

A Fabrication Strategy for Durable Slippery Organic Coating toward Antifouling and Anticorrosion via Digital Light Processing

The slippery liquid-infused porous surfaces (SLIPS) have recently attracted significant interest in marine antifouling and corrosion protection. Nevertheless, the insufficient durability and corrosion resistance of SLIPS considerably affect their application potential. In this work, a preparation strategy for ultradurable slippery organic coating was proposed to combat biofouling and corrosion. Digital light processing (DLP) was first employed to fabricate organic protective coatings with gradient porous structures to improve the stability and durability of the SLIPS. The structure with a smaller pore size in the upper segment relative to the basal area was designed to concurrently enhance the lubricant's storage and retention capabilities. The antifouling experiment demonstrated excellent antifouling performance, with a bacterial colonization of merely 2.08% after immersion in a Pseudomonas aeruginosa solution for 28 days. The antialgae assessment demonstrated that the surface antifouling efficacy of the gradient SLIPS coating was enhanced by 99.75% after a 10-day immersion period. The EIS results indicated that the SLIPS coating with a gradient porous structure exhibited remarkable corrosion resistance, as evidenced by a |Z|0.01 Hz value of 2.93 × 1010 Ω·cm2 after 60 days of immersion. The gradient porous structure effectively resolves the intrinsic dilemma between the storage and depletion of lubricant, which greatly improves the stability and durability of the SLIPS coating. The ultradurable slippery organic coating with facile preparation and controllable structure exhibits exceptional long-term antifouling and anticorrosion properties, thereby making it highly promising for potential application.

Long-lasting anti-corrosion direct-to-metal polyurethane NP-GLIDE coatings based on the coordination effect and dual cross-linking of polyphenol

Aluminum and its alloys have been widely used in our lives. However, Aluminum and its alloys is prone to corrosion, especially in harsh environment. In recent years, hydrophobic coatings were used in the corrosion protection of metal. But, the low surface tension of resins made them have a worse wettability on metal which had high surface tension, resulting in a worse adhesion of these coatings. Herein, we developed a long-lasting anti-corrosion direct-to-metal polyurethane NP-Glide coating based on the coordination effect of polyphenol and dual cross-linking. In comparative evaluation, the corrosion protection and anti-contamination performances of direct-to-metal polyurethane NP-Glide coating are significantly improved by the introduction of functional monomer dopamine methacrylamide (DMA) and TEMAc-8. The PU coatings with 10 wt% TEMAc-8 possesses high impedance value (|Z|0.01Hz > 109 Ω•cm2) after 40 days of immersion in 3.5 wt% NaCl solution, exhibiting a great pull-off adhesion both in dry and wet coating, and a long-term anti-corrosion performance for aluminum alloy protection.

Enhancing the corrosion resistance of waterborne epoxy coatings with functionalized biochar

This study utilizes discarded tree leaves as a substrate to synthesize biomass porous carbon nanosheets (PCNS) through high-temperature carbonization and pore-forming treatment, followed by functional modification using carboxymethyl chitosan (CMCS) and the corrosion inhibitor 8-hydroxyquinoline (8-HQ). The functionalized PCNS fillers were incorporated into water-based epoxy (WEP) coatings to enhance corrosion resistance. Electrochemical impedance spectroscopy (EIS) testing showed that after 60 days, WEP/PCNS@CMCS@8-HQ exhibited a low-frequency impedance of 1.7 × 109 Ω cm2 at the lowest frequency, with significantly improved salt spray corrosion performance compared to WEP. The study demonstrates that CMCS effectively captures Cl- and acts as a repair agent, working synergistically with the external corrosion inhibitor 8-HQ to improve the dispersion of PCNS within the WEP matrix and enhance corrosion resistance. These findings indicate that green-modified PCNS offers a promising approach to improving the corrosion resistance of coatings.

Constructing dual-ligand Ce-MOF on graphene oxide modified with polydopamine endowing polyurethane coating with long-term smart anti-corrosion and mechanical robustness

Traditional mono-functional anti-corrosion coatings are unable to meet the long-term corrosion resistance requirements of metal materials, therefore developing multifunctional anti-corrosion coatings have broad application prospects. In this work, long-lasting anti-corrosion coatings with superhydrophobic and self-healing properties were successfully prepared by in-situ growth of dual-ligand cerium-based metal-organic framework (Ce-MOF) on the surface of graphene oxide (GO), followed by chemical modification with polydopamine (PDA), resulting in 5B level of adhesion and excellent mechanical robustness. The superhydrophobic surface, as the external armor of the coating, can effectively block the penetrating path of corrosive media. Meanwhile, the MOF structure formed by the coordination of 2-mercaptobenzimidazole (2-M) with cerium ions endows the coating with smart self-healing properties and long-lasting corrosion resistance. Electrochemical tests showed that the low-frequency impedance modulus value of the superhydrophobic coating still reached 3.82 × 108 Ω cm2 after 30 days salt immersion. Due to the formation of protective films and insoluble precipitates at the defect site by 2-M and cerium ions, the scratches on the coating were significantly reduced after 40 days salt spray experiment, demonstrating the self-healing ability of the coating. This multifunctional anti-corrosion coating provides a new approach for preparing coatings with long-term effective corrosion resistance.

Slippery Liquid-Infused Porous Surfaces Containing UiO-66 Incorporated with 8-Hydroxyquinoline for Excellent Corrosion Protection of AZ31 Mg Alloys

The conventional slippery liquid-infused porous surfaces (SLIPSs) provide relatively limited corrosion protection and self-healing performance for AZ31 Mg alloys. To this end, 8-hydroxyquinoline (8-HQ) was incorporated into a zirconium-based metal-organic framework UiO-66 through coordination (8-HQ@UiO-66), which was then dispersed into silicone oil to fabricate nanoparticle-enhanced-SLIPSs (8-HQ@UiO-66-SLIPSs). Especially, the influences of 8-HQ@UiO-66 concentration on the surface morphology, surface hydrophobicity, and corrosion resistance were studied. It was found that the surface hydrophobicity first increased and then decreased with increasing concentration, showing the highest water contact angle of 121.2° at a concentration of 1 mg mL-1 (8-HQ@UiO-66-SLIPS-1). This was attributed to the development of well-constructed hierarchical micro/nanostructures. Moreover, it also exhibited the best anticorrosion property, with the lowest corrosion current density of 1.24 × 10-10 A cm-2 and the highest impedance modulus of 9.88 × 108 Ω cm2 at 0.01 Hz, primarily associated with the synergistic interaction of 8-HQ and UiO-66. Further, the self-healing performance was evaluated using the scanning vibration electrode technique (SVET), verifying the superior self-healing performance of 8-HQ@UiO-66-SLIPS-1. Hence, the nanoparticle-enhanced-SLIPSs exhibit considerable potential in the corrosion protection of Mg alloys, thereby accelerating their extensive applications in industry.

Research progress on chitosan and its derivatives in the fields of corrosion inhibition and antimicrobial activity

Chitosan stands out as the only known polysaccharide of its kind, second only to cellulose. As the second-largest biopolymer globally, chitosan and its derivatives are extensively used in diverse areas such as metal anti-corrosion prevention, food production, and medical fields. Its benefits include environmental friendliness, non-toxicity, cost-effectiveness, and biodegradability. Notably, the use of chitosan and its derivatives has gained substantial attention and has been extensively researched in the fields of metal anti-corrosion prevention and antibacterial applications. By means of chemical modification or synergistic action, the inherent limitations of chitosan can be substantially improved, thereby enhancing its biological and physicochemical properties to meet a wider range of applications and more demanding application requirements. This article offers a comprehensive review of chitosan and its modified composite materials, focusing on the enhancement of their anticorrosion and antibacterial properties, as well as the mechanisms by which they serve as anticorrosion and antibacterial agents. Additionally, it summarizes the synthesis routes of various modification methods of chitosan and their applications in different fields, aiming to contribute to the interdisciplinary development and potential applications of chitosan in various areas.

Ultralong-Term Durable Anticorrosive Coatings by Integration of Double-Layered Transfer Self-Healing Ability, Fe Ion-Responsive Ability, and Active/Passive Functional Partitioning

The application of self-healing polymers in corrosion protection is often limited by their slow and nonautonomous healing ability and poor long-term durability. In this paper, we propose a double-layered transfer self-healing coating constructed by soft and rigid polymer layers. The soft polymer has a fast self-healing rate of 10 min to repair, which was found to accelerate the self-healing of the upper rigid layer. The rigid polymer provided relatively high barrier ability while preserving certain self-healing ability owing to the shear-thinning effect. In this way, the double-layered coating combined rapid self-healing (∼1 h) and high impedance modulus |Z|f-0.01 Hz of 2.58 × 1010 Ω·cm2. Furthermore, the introduction of pyridine groups in B-PEA and polyacrylate-grafted-polydimethylsiloxane (PEA-g-PDMS) induced the Fe ion-responsive ability and shortened the self-healing time to 40 min (100 ppm Fe). Finally, barrier and anode sacrificed layers were introduced to produce multilayered architecture with active/passive anticorrosion performance. In the presence of scratches, the |Z|f-0.01 Hz can be preserved at 1.03 × 1010 Ω·cm2 after 200 days. The created anticorrosive coating technology combines long-term durability with room temperature autonomous rapid self-healing capability, providing a broad prospect for anticorrosive applications.

Advanced materials for smart protective coatings: Unleashing the potential of metal/covalent organic frameworks, 2D nanomaterials and carbonaceous structures

The detrimental impact of corrosion on metallic materials remains a pressing concern across industries. Recently, intelligent anti-corrosive coatings for safeguarding metal infrastructures have garnered significant interest. These coatings are equipped with micro/nano carriers that store corrosion inhibitors and release them when triggered by external stimuli. These advanced coatings have the capability to elevate the electrochemical impedance values of steel by 2-3 orders of magnitude compared to the blank coating. However, achieving intelligent, durable, and reliable anti-corrosive coatings requires careful consideration in the design of these micro/nano carriers. This review paper primarily focuses on investigating the corrosion inhibition mechanism of various nano/micro carriers/barriers and identifying the challenges associated with using them for achieving desired properties in anti-corrosive coatings. Furthermore, the fundamental aspects required for nano/micro carriers, including compatibility with the coating matrix, high specific surface area, stability in different environments, stimuli-responsive behavior, and facile synthesis were investigated. To achieve this aim, we explored the properties of micro/nanocarriers based on oxide nanoparticles, carbonaceous and two-dimensional (2D) nanomaterials. Finally, we reviewed recent literature on the application of state-of the art nanocarriers based on metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs). We believe that the outcomes of this review paper offer valuable insights for researchers in selecting appropriate materials that can effectively enhance the corrosion resistance of coatings.

Dual-Functional Eu-Metal-Organic Framework with Ratiometric Fluorescent Broad-Spectrum Sensing of Benzophenone-like Ultraviolet Filters and High Proton Conduction

The construction of attractive dual-functional lanthanide-based metal-organic frameworks (Ln-MOFs) with ratiometric fluorescent detection and proton conductivity is significant and challenging. Herein, a three-dimensional (3D) Eu-MOF, namely, [Eu4(HL)2(SBA)4(H2O)6]·9H2O, has been hydrothermally synthesized with a dual-ligand strategy, using (4-carboxypiperidyl)-N-methylenephosphonic acid (H3L = H2O3PCH2-NC5H9-COOH) and 4-sulfobenzoic acid monopotassium salt (KHSBA = KO3SC6H4COOH) as organic linkers. Eu-MOF showed ratiometric fluorescent broad-spectrum sensing of benzophenone-like ultraviolet filters (BP-like UVFs) with satisfactory sensitivity, selectivity, and low limits of detection in water/ethanol (1:1, v/v) solutions and real urine systems. A portable test paper was prepared for the convenience of actual detection. The potential sensing mechanisms were thoroughly analyzed by diversified experiments. The synergistic effect of the forbidden energy transfer from the ligand to Eu3+, the internal filtration effect (IFE), the formation of a complex, and weak interactions between the KHSBA ligand and BP-like UVFs is responsible for the ratiometric sensing effect. Meanwhile, Eu-MOF displayed relatively high proton conductivity of 2.60 × 10-4 S cm-1 at 368 K and 95% relative humidity (RH), making it a potential material for proton conduction. This work provides valuable guidance for the facile and effective design and construction of multifunctional Ln-MOFs with promising performance.

Review: Synthesis of metal organic framework-based composites for application as immunosensors in food safety

Ensuring food safety continues to be one of the major global challenges. For effective food safety monitoring, fast, sensitive, portable, and efficient food safety detection strategies must be devised. Metal organic frameworks (MOFs) are porous crystalline materials that have attracted attention for use in high-performance sensors for food safety detection owing to their advantages such as high porosity, large specific surface area, adjustable structure, and easy surface functional modification. Immunoassay strategies based on antigen-antibody specific binding are one of the important means for accurate and rapid detection of trace contaminants in food. Emerging MOFs and their composites with excellent properties are being synthesized, providing new ideas for immunoassays. This article summarizes the synthesis strategies of MOFs and MOF-based composites and their applications in the immunoassays of food contaminants. The challenges and prospects of the preparation and immunoassay applications of MOF-based composites are also presented. The findings of this study will contribute to the development and application of novel MOF-based composites with excellent properties and provide insights into advanced and efficient strategies for developing immunoassays.

CuI nanoparticle-immobilized on a hybrid material composed of IRMOF-3 and a sulfonamide-based porous organic polymer as an efficient nanocatalyst for one-pot synthesis of 2,4-diaryl-quinolines

As a significant class of synthetic and natural products with multiple biological activities, quinolines are used in medical and electronic devices. In this study, a novel method is presented to synthesize 2,4-diarylquinoline derivatives via a simple one-pot multicomponent reaction between phenylacetylenes, aniline derivatives, and aldehydes in CH₃CN using IRMOF-3/PSTA/Cu. Notably, polymer/MOF is stabilized through a reaction between a sulfonamide-triazine-based porous organic polymer [poly (sulfonamide-triazine)](PSTA) and an amino-functionalized zinc metal-organic framework (IRMOF-3). Next, the prepared nanocomposites (IRMOF-3/PSTA) are modified using copper iodide nanoparticles (CuI NPs). Overall, the high product yields, facile recovery of nanocatalysts, short reaction times, and broad substrate range make this process environmentally friendly, practical, and economically justified.