A one-step assembly method using coordination complexes of natural polyphenols and Fe(III) ions is reported for the conformal coating of various substrates to produce versatile thin films and particles. The method involves the adsorption of tannic acid (TA) and Fe(III) ions in water, with film formation directed by pH-dependent, multivalent coordination bonding. The technique allows rapid production of structurally diverse, disassembling films and capsules on a wide range of substrates, including planar and particulate templates. The process is simple, low-cost, and scalable, with pH-responsiveness and negligible cytotoxicity, making it suitable for biomedical and environmental applications. The natural polyphenol TA and Fe(III) ions are used as organic ligands and inorganic cross-linkers, respectively. Film deposition occurs upon mixing TA and Fe(III) in water at ambient temperature. The resulting films are highly uniform and can be used to create hollow capsules by dissolving the templates. These capsules have applications in drug delivery, catalysis, biosensing, and microreactors. The films are confirmed to contain Fe and TA, and their properties are analyzed using various microscopy and spectroscopy techniques. The thickness and morphology of the films are influenced by the concentrations of TA and Fe(III). The films are found to be more stable at higher pH values and disassemble in response to pH changes. The method is versatile, as it can be applied to various substrates, including glass, gold, PDMS, PLGA, and biological materials. The films are also pH-responsive, with disassembly occurring at low pH values. The films are non-toxic and have potential biomedical applications due to their pH-sensitive disassembly profile. The method is further demonstrated using different metals and polyphenols, showing its general applicability. The films are simple to prepare and have biologically relevant physicochemical properties, making them suitable for advanced material engineering.A one-step assembly method using coordination complexes of natural polyphenols and Fe(III) ions is reported for the conformal coating of various substrates to produce versatile thin films and particles. The method involves the adsorption of tannic acid (TA) and Fe(III) ions in water, with film formation directed by pH-dependent, multivalent coordination bonding. The technique allows rapid production of structurally diverse, disassembling films and capsules on a wide range of substrates, including planar and particulate templates. The process is simple, low-cost, and scalable, with pH-responsiveness and negligible cytotoxicity, making it suitable for biomedical and environmental applications. The natural polyphenol TA and Fe(III) ions are used as organic ligands and inorganic cross-linkers, respectively. Film deposition occurs upon mixing TA and Fe(III) in water at ambient temperature. The resulting films are highly uniform and can be used to create hollow capsules by dissolving the templates. These capsules have applications in drug delivery, catalysis, biosensing, and microreactors. The films are confirmed to contain Fe and TA, and their properties are analyzed using various microscopy and spectroscopy techniques. The thickness and morphology of the films are influenced by the concentrations of TA and Fe(III). The films are found to be more stable at higher pH values and disassemble in response to pH changes. The method is versatile, as it can be applied to various substrates, including glass, gold, PDMS, PLGA, and biological materials. The films are also pH-responsive, with disassembly occurring at low pH values. The films are non-toxic and have potential biomedical applications due to their pH-sensitive disassembly profile. The method is further demonstrated using different metals and polyphenols, showing its general applicability. The films are simple to prepare and have biologically relevant physicochemical properties, making them suitable for advanced material engineering.