-3) were realized by double stimulation of temperature and solvent, which were accomplished by single-crystal to single-crystal (SC-SC) reaction.

Three coordination polymers, namely, {[Co(L 1 )(HBTC)]•0.5L 1 , have been synthesized based on three semi-rigid nitrogen-containing ligands (L 1 = 4,4'-(2,5-dimethoxy-1,4-phenylene)dipyridine; L 2 = 4,4'-(2,5-diethoxy-1,4-phenylene)dipyridine; L 3 = 4,4'-(2,5-dibutoxy-1,4-phenylene)dipyridine) and 1,3,5-benzenetricarboxylic acid (H 3 BTC). Both I and II are a 4-connected uninodal sql net with point symbol {4 4 •6 2 }, III is a 6-connected uninodal rob net with point symbol {4 8 •6 6 •8}. The complexes were characterized by X-ray single-crystal diffraction (CIF files CCDC nos. 2034103 (II), 2034104 (III)), PXRD, IR spectra and TGA. Interestingly, the structural diversity of these complexes derived from the length of substituents on L n (n = 1, 2, 3) ligands.

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Precise construction of stimuli-responsive MOF (SRMOF) materials with excellent catalytic properties is a daunting challenge. Herein, two flexible ligands 4,4′,4″-(nitrilotris(methylene))tribenzoic acid (H3L) and 1,4-bis((1H-imidazol-1-yl)methyl)benzene (BMB) have been used to construct a Cd-MOF (AQNU-5, AQNU named Anqing Normal University) containing three-dimensional pores and rod SBUs. Due to the flexible ligand-induced dynamic framework, AQNU-5 exhibits structural flexibility with stimuli-responsive properties in photocatalytic CO2 reduction, which depends on both temperature and solvent. The results showed that the CO2-to-CO reduction rate reached an optimum of 56.2 μmol g–1 h–1 at 150 °C without the addition of any photosensitizer. Interestingly, this dynamic response is reversible, with the skeleton remaining unchanged from the parent structure before and after the catalytic reaction. The strategy of using flexible ligands in this work may provide a unique opportunity to obtain novel crystal framework materials with desirable properties.

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