TA/Fe(III) anti-chloride coating to protect concrete

Recent Progress in Membrane Technologies Based on Metal–Phenolic Networks: A Review

“…Polyphenols, the nontoxic phenolic substances, are abundantly present in plants. , They have plentiful fascinating physicochemical properties, such as metal chelation, radical scavenging, hydrogen bonding, and antioxidant. ,− Tannic acid (TA) with the chemical formula of C 76 H 52 O 46 is the most commonly used natural polyphenol in the field of the advanced material science and engineering, due to its numerous fascinating properties. TA, the weak natural organic acid (p K a around 10) whose molecule contains five constituents of hydrophilic digalloyl esters which are covalently bonded to a central hydrophobic core as shown in Figure , is amphipathic due to its strong affinity to both polar and nonpolar substances. ,, …”

“…Moreover, due to being a polydentate ligand substance, TA can undergo coordination reactions with metal ions to form porous supramolecular complexes, ,,, which are interesting advanced nanomaterials that can be applied in numerous technological fields. During MPN-complex formation through coordination interaction, catechol or galloyl hydroxyl oxygen atoms contained in TA molecules usually serve as the metal chelating sites to form covalent and noncovalent bonds with central metal cations. , …”

“…The constituent MPN-building blocks or the supramolecular physical appearances are mainly used to classify the materials. Based on the type and singularity or multiplicity of the MPN-building blocks, there are monometal–monoligand MPNs, ,, multimetal–monoligand MPNs, monometal–multiligand MPNs, and multimetal–multiligand MPNs . Since each MPN-building block has certain intrinsic characteristics, appropriate types of metal cations or phenolic ligands can be mixed to fabricate supramolecular materials with improved multifunctional properties, such as MPN particles (microcapsules), , MPN films, ,,, and MPN bulk materials …”

“…MPNs can encapsulate commonly used inorganic nanomaterials and reduce their natural aggregation in catalytic reactions, owing to their recyclability and tunable porosity. ,, Also, MPN capsules can serve as microreactors in microprocesses. , In addition, due to the acidity-dependent disassembly, MPN capsules can be used for drug delivery, biosensing, and bioimaging. ,,,, MPN films, mixed or unmixed with other organic or inorganic materials, can be applied on various surfaces for diverse applications, for instance, membranes for liquid filtration improvements, ,− base metals, or base metal containing structures for corrosion prevention . MPN bulk materials, due to having strong sticking ability, can serve as mechanical adhesive agents .…”

“…The multistep MPN-film formation involves the alternation of the submergence of a substrate between the two separate MPN-building block solutions, one containing organic ligands and the other containing inorganic cross-linkers, with an intermediate rinsing to remove unadsorbed species from the substrate to avoid unwanted MPN aggregate formation in the two solutions, ,,,,,, as illustrated in Figure . In the multistep MPN-film formation, the film thickness normally grows discretely on a substrate surface when the quantity of the deposited materials increases as the acidity decreases. , Thus, the ultimate MPN-film thickness is determined by the level of acidity of the coating solutions.…”