Robust Multifunctional Yttrium-Based Metal–Organic Frameworks with Breathing Effect

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• 作者：Ana D. G. Firmino ; Ricardo F. Mendes ; Margarida M. Antunes ; Paula C. BarbosaSérgio M. F. Vilela ; Anabela A. Valente ; Filipe M. L. Figueiredo ; João P. C. Tomé ; Filipe A. Almeida Paz
• 刊名：Inorganic Chemistry
• 出版年：2017
• 出版时间：February 6, 2017
• 年：2017
• 卷：56
• 期：3
• 页码：1193-1208
• 全文大小：857K
• ISSN：1520-510X

文摘

Phosphonate- and yttrium-based metal–organic frameworks (MOFs), formulated as [Y(Hb>5b>btp)]·5.5Hb>2b>O (<b>1b>), [Y(Hb>5b>btp)]·2.5Hb>2b>O (<b>2b>), (Hb>3b>O)[Yb>2b>(Hb>5b>btp)(Hb>4b>btp)]·Hb>2b>O (<b>3b>), and [Y(Hb>5b>btp)]·Hb>2b>O·0.5(MeOH) (<b>4b>), 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) (Hb>8b>btp) 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 <b>2b> and <b>3b> were further studied to ascertain their performance as heterogeneous catalysts and proton conductors, respectively, with outstanding results being registered for both materials. Compound <b>2b> 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 <b>3b> at 98% of relative humidity (2.58 × 10^–2 S 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.