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The one-pot reaction of Cd(NO)·4HO and 5-(6-(hydroxymethyl)pyridin-3-yl)isophthalic acid (HL) in DMF/HO (DMF = N,N-dimethylformamide) produced a two-dimensional (2D) metal-organic framework (MOF) of [Cd(L)(HO)] (A) bearing aqua-bridged Cd centers, accompanied by two three-dimensional (3D) MOFs [Cd(L)(DMF)] (B) and [Cd(L)] (C). Removing the bridging aqua molecules of A by heating led to the formation of an additional 3D MOF of [Cd(L)] (D) in a single-crystal to single-crystal (SCSC) manner. The search for the preceding compound that could convert to A resulted in the isolation of a 2D MOF [Cd(L)(DMF)] (E) that readily converted to A in water, but with the loss of single crystallinity. Upon excitation at 350 nm, A, D, E, and the ligand HL fluoresced at 460 nm, 468 nm, 475 nm, and 411 nm, respectively. The fluorescence of A could be used for the selective detection of Fe in water down to 0.58 ppm. This quenching was not affected by the presence of other common metal ions.

What is the most significant result of this study?We demonstrated the isolation of emissive zwitterions that are intermediates in the metal-organic framework assembly process. These simple zwitterions are structurally interesting (for another paper on the isolation of transition-metal-based zwitterions, see: RSC Adv. 2015, 5,4 2978). We also showed, for the first time, that pyridine alcohol/carboxylate hybrid ligands are suitable for construction of apotentially diverse class of porous materials.

This article uses investigations into two villages to scrutinise the politics of space and visuality in the top-down development of nostalgia tourism across the Chinese countryside engineered by the government since 2014. It goes beyond the debate between the representational and non-representational approaches in tourist landscape studies and proposes the concept of ‘embodied scopic regimes’ as a more nuanced framework of analysis. It is argued that the landscape production in the current development of nostalgia tourism in China is featured by the coexistence and entanglement of three different embodied scopic regimes: ‘stop/gaze regime’, ‘flâneur/glance regime’ and ‘choraster/spectacle regime’. Each regime produces a unique fashion of visual pleasure and distinct mode of physical movements, manifested and afforded by different sets of cultural technologies. The operation of these multiple regimes also diversifies the meanings of nostalgia that these tourist sites claim to represent, which allows the overlapping between ‘reflective nostalgia’ and ‘restorative nostalgia’ in the same space. Based on this unique case, the article engages with the ‘landscape debate’ in critical tourist studies and extends the common ground between the two seemingly oppositional approaches.

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