{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,5]],"date-time":"2026-05-05T13:35:07Z","timestamp":1777988107533,"version":"3.51.4"},"reference-count":32,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2025,3,6]],"date-time":"2025-03-06T00:00:00Z","timestamp":1741219200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Tunisian Ministry of Higher Education and Scientific Research"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Solids"],"abstract":"<jats:p>With the rapid increase in polyethylene terephthalate (PET) usage in recent years, recycling has become indispensable in mitigating environmental damage and safeguarding natural resources. In this context, this study presents a methodology for valorizing PET waste through phase transfer catalytic hydrolysis conducted at a low temperature (80 \u00b0C) and atmospheric pressure, with the goal of recovering the terephthalic acid (TPA) monomer. The recovered TPA monomer was subsequently utilized as a precursor for the synthesis of metal\u2013organic frameworks (MOFs). Tributylhexadecyl phosphonium bromide (3Bu6DPB) was selected as the phase transfer catalyst due to its efficiency and sustainability. The process parameters, including the concentration of NaOH, the wt.% of catalyst to PET, and the concentration of PET in the solution, were varied to optimize the hydrolysis reaction. The Taguchi design methodology with an L9 (3^3) orthogonal array was employed to analyze the influence of these factors on the depolymerization time. The analysis of variance (ANOVA) results revealed that the concentration of NaOH was the most significant factor, contributing to 93.3% of the process efficiency, followed by the wt.% of the catalyst to PET (6.5%). The findings also demonstrated that the concentration of NaOH had the greatest impact (\u0394 = 4.27, rank = 1), while the concentration of PET had the smallest effect (\u0394 = 0.16, rank = 3). The optimal conditions for PET depolymerization were achieved in 75 min with 20 g\/100 mL of NaOH, 12 wt.% of catalyst to PET, and 5 g\/100 mL of PET. The recovered TPA monomer was further employed as an organic ligand to synthesize Fe(III)-TPA MOFs under mild conditions (80 \u00b0C for 24 h). The X-ray diffraction (XRD) analysis revealed the simultaneous formation of MOF-235(Fe) and MIL-101(Fe), two multifunctional materials with diverse properties and applications. This study highlights an efficient approach for producing low-cost MOFs while promoting urban waste recycling, contributing to an integrated strategy for PET recycling and resource valorization.<\/jats:p>","DOI":"10.3390\/solids6010010","type":"journal-article","created":{"date-parts":[[2025,3,6]],"date-time":"2025-03-06T04:55:08Z","timestamp":1741236908000},"page":"10","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["Taguchi Robust Design of Phase Transfer Catalytic Hydrolysis of Polyethylene Terephthalate (PET) Waste in Mild Conditions: Application for the Preparation of Metal\u2013Organic Frameworks"],"prefix":"10.3390","volume":"6","author":[{"given":"Asma","family":"Nouira","sequence":"first","affiliation":[{"name":"Renewable Energies Chair, Polo da Mitra da Universidade de \u00c9vora, P\u00f3lo da Mitra, Apartado 94, 7006-554 \u00c9vora, Portugal"},{"name":"Laboratory of Composite Materials and Clay Minerals (LMCMA), CNRSM-Technopole Borj C\u00e9dria, Universiy of Carthage, BP 73, Soliman 8027, Tunisia"},{"name":"Faculty of Sciences of Tunis, University of Tunis El Manar, Rue de Tol\u00e8de, Tunis 2092, Tunisia"}]},{"given":"Imene","family":"Bekri-Abbes","sequence":"additional","affiliation":[{"name":"Laboratory of Composite Materials and Clay Minerals (LMCMA), CNRSM-Technopole Borj C\u00e9dria, Universiy of Carthage, BP 73, Soliman 8027, Tunisia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2085-9157","authenticated-orcid":false,"given":"Isabel Pestana","family":"Paix\u00e3o Cansado","sequence":"additional","affiliation":[{"name":"Departamento de Qu\u00edmica e Bioqu\u00edmica, Escola de Ci\u00eancias e Tecnologia, MED\u2014Mediterranean Institute for Agriculture, Environment and Development & Change\u2013Global Change and Sustainability Institute, Universidade de \u00c9vora, Rua Rom\u00e3o Ramalho n\u00ba 59, 7000-671 \u00c9vora, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3634-2390","authenticated-orcid":false,"given":"Paulo Alexandre Mira","family":"Mour\u00e3o","sequence":"additional","affiliation":[{"name":"Departamento de Qu\u00edmica e Bioqu\u00edmica, Escola de Ci\u00eancias e Tecnologia, MED\u2014Mediterranean Institute for Agriculture, Environment and Development & Change\u2013Global Change and Sustainability Institute, Universidade de \u00c9vora, Rua Rom\u00e3o Ramalho n\u00ba 59, 7000-671 \u00c9vora, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2025,3,6]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1146\/annurev-environ-102016-060700","article-title":"Plastic as a persistent marine pollutant","volume":"42","author":"Worm","year":"2017","journal-title":"Annu. Rev. Environ. Resour."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"77","DOI":"10.5802\/crchim.214","article-title":"Valorisation of plastic waste from the beverage industry through its transformation into adsorbent and solid fuel materials","volume":"26","author":"Nouira","year":"2022","journal-title":"Comptes Rendus. Chim."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"41","DOI":"10.1007\/s10965-024-03883-y","article-title":"A study on microwave-assisted chemical recycling of polyethylene terephthalate (PET) waste","volume":"31","author":"Allaf","year":"2024","journal-title":"J. Polym. Res."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1893","DOI":"10.1039\/D2PY01520J","article-title":"Thermo-responsive polymer catalysts for polyester recycling processes: Switching from homogeneous catalysis to heterogeneous separations","volume":"14","author":"Stumpf","year":"2023","journal-title":"Polym. Chem."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"2651","DOI":"10.1002\/pen.26406","article-title":"A focused review on recycling and hydrolysis techniques of polyethylene terephthalate","volume":"63","author":"Abedsoltan","year":"2023","journal-title":"Polym. Eng. Sci."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"7609","DOI":"10.1016\/j.polymer.2003.09.062","article-title":"Simultaneous glycolysis and hydrolysis of polyethylene terephthalate and characterization of products by differential scanning calorimetry","volume":"44","author":"Orbay","year":"2003","journal-title":"Polymer"},{"key":"ref_7","unstructured":"Rosen, B.I. (1992). Preparation of Purified Terephthalic Acid from Waste Polyethylene Terephthalate. (5,095,145), U.S. Patent."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Aguado, J., and Serrano, D. (1999). Recycling of Plastic Wastes, University of York.","DOI":"10.1039\/9781847550804"},{"key":"ref_9","unstructured":"Nikolaevich, L., Vladimirovna, I., and Zulfatovich, M. (2017). Method for Waste Pet Alkaline Hydrolysis with Terephthalic Acid Production. (RU2616299C1), RU Patent."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"640","DOI":"10.1002\/1439-2054(20011001)286:10<640::AID-MAME640>3.0.CO;2-1","article-title":"Poly (ethylene terephthalate) recycling and recovery of pure terephthalic acid. Kinetics of a phase transfer catalyzed alkaline hydrolysis","volume":"286","author":"Kosmidis","year":"2001","journal-title":"Macromol. Mater. Eng."},{"key":"ref_11","first-page":"511","article-title":"Chemical recycling of PET by alkaline hydrolysis in the presence of quaternary phosphonium and ammonium salts as phase transfer catalysts","volume":"109","year":"2008","journal-title":"WIT Trans. Ecol. Environ."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"145453","DOI":"10.1016\/j.cej.2023.145453","article-title":"A sustainable chrome-free tanning approach based on Zr-MOFs functionalized with different metals through post-synthetic modification","volume":"474","author":"Chen","year":"2023","journal-title":"Chem. Eng. J."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"135263","DOI":"10.1016\/j.jclepro.2022.135263","article-title":"An eco-friendly metal-less tanning process: Zr-based metal-organic frameworks as novel chrome-free tanning agent","volume":"382","author":"Chen","year":"2023","journal-title":"J. Clean. Prod."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Manousi, N., Zachariadis, G., Deliyanni, E., and Samanidou, V. (2018). Applications of metal-organic frameworks infood sample preparation. Molecules, 23.","DOI":"10.3390\/molecules23112896"},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Giliopoulos, D., Zamboulis, A., Giannakoudakis, D., Bikiaris, D., and Triantafyllidis, K. (2020). Polymer\/Metal OrganicFramework (MOF) Nanocompositesfor biomedical applications. Molecules, 25.","DOI":"10.3390\/molecules25010185"},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Kampouraki, Z., Giannakoudakis, D., Nair, V., Hosseini-Bandegharaei, A., Colmenares, J., and Deliyanni, E. (2019). Metal organic frameworks as desulfurization adsorbents of dbt and 4,6-dmdbt from fuels. Molecules, 24.","DOI":"10.3390\/molecules24244525"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"2497","DOI":"10.1021\/acsami.3c15669","article-title":"Ultrarapid and sustainable synthesis of trimetallic-based mof (crnife-mof) from stainless steel and disodium terephthalate-derived PET wastes","volume":"16","author":"Boukayouht","year":"2024","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Zhang, F., Chen, S., Nie, S., Luo, J., Lin, S., Wang, Y., and Yang, H. (2019). Waste PET as a reactant for lanthanide MOF synthesis and application in sensing of picric acid. Polymers, 11.","DOI":"10.3390\/polym11122015"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"2998","DOI":"10.1021\/ic050064g","article-title":"Metal-organic frameworks based on trigonal prismatic building blocks and the new \u201cacs\u201d topology","volume":"44","author":"Sudik","year":"2005","journal-title":"Inorg. Chem."},{"key":"ref_20","unstructured":"Unal, R., and Dean, E.B. (1991, January 1). Taguchi approach to design optimization for quality and cost: An overview. Proceedings of the 1991 Annual Conference of the International Society of Parametric Analysts, NASA Langley Research Center, Hampton, VA, USA."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"109823","DOI":"10.1016\/j.jece.2023.109823","article-title":"Chemical recycling of monolayer PET tray waste by alkaline hydrolysis","volume":"11","author":"Barredo","year":"2023","journal-title":"J. Environ. Chem. Eng."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"3404","DOI":"10.3390\/ma6083404","article-title":"Optimization of microwave-based heating of cellulosic biomass using Taguchi method","volume":"6","author":"Tseng","year":"2013","journal-title":"Materials"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"30","DOI":"10.1002\/masy.201400269","article-title":"Characterization of Terephthalic Acid Monomer Recycled from Post-Consumer PET Polymer Bottles","volume":"361","author":"Ravichandran","year":"2016","journal-title":"Macromol. Symp."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Chinglenthoiba, C., Mahadevan, G., Zuo, J., Prathyumnan, T., and Valiyaveettil, S. (2024). Conversion of PET Bottle Waste into a Terephthalic Acid-Based Metal-Organic Framework for Removing Plastic Nanoparticles from Water. Nanomaterials, 14.","DOI":"10.3390\/nano14030257"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"113","DOI":"10.1080\/07370652.2015.1005773","article-title":"Determination of the Thermal Decomposition Products of Terephthalic Acid by Using Curie-Point Pyrolyzer","volume":"34","author":"Kimyonok","year":"2016","journal-title":"J. Energetic Mater."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"100393","DOI":"10.1016\/j.dwt.2024.100393","article-title":"Iron terephthalate metal-organic framework (MOF-235) modified with zinc as an efficient adsorbent for removal of tetracycline from aqueous solution","volume":"318","author":"Salem","year":"2024","journal-title":"Desalination Water Treat."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"4035075","DOI":"10.1155\/2019\/4035075","article-title":"An Effective Microwave-Assisted Synthesis of MOF235 with Excellent Adsorption of Acid Chrome Blue","volume":"2019","author":"Ge","year":"2019","journal-title":"J. Nanomater."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"16395","DOI":"10.1039\/C5RA24915E","article-title":"Facile synthesis of MOF 235 and its superior photocatalytic capability under visible light irradiation","volume":"6","author":"Li","year":"2016","journal-title":"RSC Adv."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"121150","DOI":"10.1016\/j.jssc.2019.121150","article-title":"Synthesis of MIL-101(Fe)\/SiO2 composites with improved catalytic activity for reduction of nitroaromatic compounds","volume":"283","author":"Huang","year":"2020","journal-title":"J. Solid State Chem."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"4976","DOI":"10.1039\/D0DT04341A","article-title":"Experimental investigations into the irregular synthesis of iron(III) terephthalate metal\u2013organic frameworks MOF-235 and MIL-101","volume":"50","author":"Simonsson","year":"2021","journal-title":"Dalton Trans."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"5565","DOI":"10.1007\/s11581-020-03735-x","article-title":"Facile synthesis of Fe-based metal-organic framework and graphene composite as an anode material for K-ion batteries","volume":"26","author":"Deng","year":"2020","journal-title":"Ionics"},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Villarroel-Rocha, D., Garc\u00eda-Carvajal, C., Amaya-Roncancio, S., Villarroel-Rocha, J., Torres-Ceron, D.A., Restrepo-Parra, E., and Sapag, K. (2024). MIL-101(Fe)@ceramic-monolith for arsenic removal in aqueous solutions. Sci. Rep., 14.","DOI":"10.1038\/s41598-024-80400-7"}],"container-title":["Solids"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2673-6497\/6\/1\/10\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,9]],"date-time":"2025-10-09T16:48:06Z","timestamp":1760028486000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2673-6497\/6\/1\/10"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,3,6]]},"references-count":32,"journal-issue":{"issue":"1","published-online":{"date-parts":[[2025,3]]}},"alternative-id":["solids6010010"],"URL":"https:\/\/doi.org\/10.3390\/solids6010010","relation":{"is-referenced-by":[{"id-type":"doi","id":"10.1007\/s10853-026-12679-y","asserted-by":"object"}]},"ISSN":["2673-6497"],"issn-type":[{"value":"2673-6497","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,3,6]]}}}