title: Robust Multifunctional Yttrium-Based Metal-Organic Frameworks with Breathing Effect.
abstract: Phosphonate- and yttrium-based metal-organic frameworks (MOFs), formulated as [Y(H5btp)]·5.5H2O (1), [Y(H5btp)]·2.5H2O (2), (H3O)[Y2(H5btp)(H4btp)]·H2O (3), and [Y(H5btp)]·H2O·0.5(MeOH) (4), were prepared using a "green" microwave-assisted synthesis methodology which promoted the self-assembly of the tetraphosphonic organic linker [1,1'-biphenyl]-3,3',5,5'-tetrayltetrakis(phosphonic acid) (H8btp) with Y3+cations. This new family of functional materials, isolated in bulk quantities, exhibits a remarkable breathing effect. Structural flexibility was thoroughly studied by means of X-ray crystallography, thermogravimetry, variable-temperature X-ray diffraction, and dehydration and rehydration processes, ultimately evidencing a remarkable reversible single-crystal to single-crystal (SC-SC) transformation solely through the loss and gain of crystallization solvent molecules. Topologically, frameworks remained unaltered throughout this interconversion mechanism, with all compounds being binodal 6,6-connected network with a Schäfli symbol of {413.62}{48.66.8}. Results show that this is one of the most stable and thermally robust families of tetraphosphonate-based MOFs synthesized reported to date. Porous materials 2 and 3 were further studied to ascertain their performance as heterogeneous catalysts and proton conductors, respectively, with outstanding results being registered for both materials. Compound 2 showed a 94% conversion of benzaldehyde into (dimethoxymethyl)benzene after just 1 h of reaction, among the best results registered to date for MOF materials. On the other hand, the protonic conductivity of compound 3 at 98% of relative humidity (2.58 × 10-2S cm-1) was among the highest registered among MOFs, with the great advantage of the material to be prepared using a simpler and sustainable synthesis methodology, as well as exhibiting a good stability at ambient conditions (temperature and humidity) over time when compared to others.
authors.affiliation: Department of Chemistry, CICECO-Aveiro Institute of Materials, University of Aveiro , 3810-193 Aveiro, Portugal.|Department of Chemistry, QOPNA, University of Aveiro , 3810-193 Aveiro, Portugal.
authors.forename: Ana D G
authors.initials: AD
authors.lastname: Firmino
authors.affiliation: Department of Chemistry, CICECO-Aveiro Institute of Materials, University of Aveiro , 3810-193 Aveiro, Portugal.
authors.forename: Ricardo F
authors.initials: RF
authors.lastname: Mendes
authors.affiliation: Department of Chemistry, CICECO-Aveiro Institute of Materials, University of Aveiro , 3810-193 Aveiro, Portugal.
authors.forename: Margarida M
authors.initials: MM
authors.lastname: Antunes
authors.affiliation: Department of Materials & Ceramic Engineering, CICECO - Aveiro Institute of Materials, University of Aveiro , 3810-193 Aveiro, Portugal.
authors.forename: Paula C
authors.identifier: http://orcid.org/0000-0002-6983-2329
authors.initials: PC
authors.lastname: Barbosa
authors.affiliation: Department of Chemistry, CICECO-Aveiro Institute of Materials, University of Aveiro , 3810-193 Aveiro, Portugal.|Department of Chemistry, QOPNA, University of Aveiro , 3810-193 Aveiro, Portugal.
authors.forename: Sérgio M F
authors.initials: SM
authors.lastname: Vilela
authors.affiliation: Department of Chemistry, CICECO-Aveiro Institute of Materials, University of Aveiro , 3810-193 Aveiro, Portugal.
authors.forename: Anabela A
authors.initials: AA
authors.lastname: Valente
authors.affiliation: Department of Materials & Ceramic Engineering, CICECO - Aveiro Institute of Materials, University of Aveiro , 3810-193 Aveiro, Portugal.
authors.forename: Filipe M L
authors.initials: FM
authors.lastname: Figueiredo
authors.affiliation: Department of Chemistry, QOPNA, University of Aveiro , 3810-193 Aveiro, Portugal.|Centro de Química Estrutural, Instituto Superior Técnico, University of Lisbon , Avenida Rovisco Pais, 1049-001 Lisbon, Portugal.
authors.forename: João P C
authors.initials: JP
authors.lastname: Tomé
authors.affiliation: Department of Chemistry, CICECO-Aveiro Institute of Materials, University of Aveiro , 3810-193 Aveiro, Portugal.
authors.forename: Filipe A Almeida
authors.identifier: http://orcid.org/0000-0003-2051-5645
authors.initials: FA
authors.lastname: Paz