| In this paper,we propose a design strategy for assembly of metal-coordinated calix[4]resorcinarene cavitands and cages by tuning of the ancillary linkers.A series of metal-coordinated cavitands and cages constructed from calix[4]resorcinarene,Zn?II?ions and different isophthatic acids analogs have been synthesized under solvothermal conditions.They were characterized by X-ray diffraction,powder X-ray diffraction spectra?PXRD?,thermogravimetric analysis?TGA?,element analyses and infrared spectra?IR?.The synthesis conditions,crystal stuctures and influences of ancillary linkers with different angular and size on the structure of final products have been investigated.According to the structural feature and stability,the adsorption properties have also been studied in detail.1.Three cavitand compounds 1a,1b and 1c were constructed from calix[4]resorcinarene,Zn?II?ions and isophthatic acids analogs under solvothermal conditions.[Zn4?Me-TPC4R??L1?4]·6DMF·2H2O?1a?[Zn4?Me-TPC4R??L2?4]·3DMF·H2O?1b?[Zn4?Me-TPC4R??L3?4]·5DMF?1c??H2L1=5-aminoisophthalic acid,H2L2=5-hydroxyisophthalic acid,H2L3=5-?pyridin-4-yl?isophthalic acid,DMF=N,N'-dimethylformamide?.1a,1b and 1c are isostructural.Remarkably,they exhibit high structural flexibilities,reversibly transforming between the open-pore and the narrow-pore structures,upon removal and sorption of guest molecules,as evidenced by diffraction and gas adsorption measurements.By combining experimental studies with density functional theory?DFT?calculations,we thoroughly elucidated the mechanism of the structural transformations in response to external stimuli.2.Inspired and motivated by the successful preparation of the metal-coordinated cavitands,we envision that tetracarboxylic acid analogs with appropriate spacers between two isophthalic acids may link two cavitands into tunable cages in the presence of Zn?II?ions.Three tetracarboxylic acid analogs H4L4?H4L5 and H4L6 were synthesized.A family of nanoscale calix[4]resorcinarene-based cages 2a,2b and 2c were synthesized by joining two metal-coordinated calix[4]resorcinarene cavitands.[Zn8?Me-TPC4R?2?L4?4]·5DMF·20H2O?2a?[Zn8?Pen-TPC4R?2?L5?4]·7DMF?2b?[Zn8?Pen-TPC4R?2?L6?4]·6DMF?2c?H4L4=5,5'-methylene-bis?oxy?diisophthalic acid,H4L5=5,5'-?1,3-phenylenebis?methylene??bis?oxy?diisophthalic acidH4L6=5,5'-?1,4-phenylenebis?methylene??bis?oxy?diisophthalic acidWe performed detailed gas adsorption measurements,using 2a as a representative.N2 adsorption isotherm at 77 K indicates that 2a has a permanent porosity with a fully reversible type-I behavior.The maximum N2 uptake is320cm3·g-1?In addition,the high-pressure CO2 and CH4 adsorption capacities of 2a have also been investigated,the CO2 and CH4 adsorption of 2a can reach a maximum uptake of 257 cm3?STP?/g and 157 cm3?STP?/g,respectively,showing the potential of2a as a promising supramolecular porous material for CH4 storage.3.Two octahedral cages were constructed from calix[4]resorcinarene,Zn?II?and rigid tetracarboxylic acid analogs H4L7and H4L8under solvothermal condition.[Zn24?Pen-TPC4R?6?L7?12]·Xsolvents?3a?[Zn24?Pen-TPC4R?6?L8?12]·Xsolvents?3b?H4L7=3,3',5,5'-azobenzenetetracarboxylic acidH4L8=p-Terphenyl-3,3'',5,5''-tetracarboxylic acidUnlike the cages in our preliminary work,the volumes of 3a and 3b are considerable.The structures of 3a and 3b contain 6 calix[4]resorcinarene ligands,24Zn?II?ions,and 12 rigid tetracarboxylic acids.Activated 3a has the ability to adsorb iodine vapor.The iodine vapor adsorption of 3a can reach a maximum uptake of142wt%at 75?.Furthermore,3a can also remove iodine from normal hexane solution,a nanocage of 3a can accommodate 12.2 iodine guest molecules. |
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