Crystalline Porous Organic Frameworks Based on Multiple Dynamic Linkages.

A novel class of crystalline porous materials has been developed utilizing multilevel dynamic linkages, including covalent B-O, dative B←N and hydrogen bonds. Typically, boronic acids undergo in situ condensation to afford B3O3-based units, which further extend to molecular complexes or chains via B←N bonds. The obtained superstructures are subsequently interconnected via hydrogen bonds and π-π interactions, producing crystalline porous organic frameworks (CPOFs). The CPOFs display excellent solution processability, allowing dissolution and subsequent crystallization to their original structures, independent of recrystallization conditions, possibly due to the diverse bond energies of the involved interactions. Significantly, the CPOFs can be synthesized on a gram-scale using cost-effective monomers. In addition, the numerous acidic sites endow the CPOFs with high NH3 capacity, surpassing most porous organic materials and commercial materials.

Two Robust In(III)-Based Metal-Organic Frameworks with Higher Gas Separation, Efficient Carbon Dioxide Conversion, and Rapid Detection of Antibiotics.

With the aid of a pyridyl tetracarboxylate ligand, 2,5-bis(2',5'-dicarboxylphenyl)pyridine (H4L), two indium-organic frameworks, [In2(L)(OH)2]·2DMF·2H2O (1) and [Me2NH2][In(L)]·2.5NMF·4H2O (2), with (6,8)- and (4,4)-connected nets have been constructed in different solvent systems. Both 1 and 2 exhibit high thermal and chemical stability. Gas sorption behavior of 1 and 2 for N2, C2H2, C2H4, CO2, and CH4 indicate excellent separation selectivities of C2Hx/CH4 and CO2/CH4. Furthermore, 1 possesses a high density of Brønsted sites and shows efficient catalytic conversion for CO2 cycloaddition with epoxides. Meanwhile, luminescence investigations reveal that 2 can detect nitrofurazone efficiently.

Two Stable Terbium-Organic Frameworks Based on Predesigned Functionalized Ligands: Selective Sensing of Fe3+ Ions and C2H2/CH4 Separation.

To construct desired metal-organic framework (MOF) sensors, the predesigned functionalized ligands 2,5-bis(2',5'-dicarboxylphenyl)pyridine (L-N) and 2,5-bis(2',5'-dicarboxylphenyl)difluorobenzene (L-F) with pyridine- and fluorine-decorated tetracarboxylic acids were used, and two stable terbium-organic frameworks, H3O[(Tb(L-N)(H2O)2]·2H2O (Tb-N) and [Tb3(L-F)2(HCOO)(H2O)4]·6H2O (Tb-F), have been synthesized. The structures of Tb-N and Tb-F contain 1D open channels, which are functionalized by pyridine N or F atoms, respectively. Both of them show intense fluorescence in water and exhibit excellent selectivity and sensitivity to Fe3+ ions. The effects of different functional group sites on the stability and fluorescence sensing performance of MOFs have also been studied. In addition, a gas adsorption study demonstrates that Tb-N is capable of adsorbing C2H2 over CH4 selectively.

Sieving Effect for the Separation of C2 H2 /C2 H4 in an Ultrastable Ultramicroporous Zinc-Organic Framework.

The separation of C2 H2 from C2 H4 is one of the most challenging tasks due to the similarity of their physical properties. In addition, green synthetic protocol and adsorbent's stability are also the major concerns during the separation. Herein, under hydrothermal green synthesis conditions, an ultrastable ultramicroporous Zn-MOF was designed and synthesized with a high yield. The pore diameter of the Zn-MOF is 3.6 Å, which lies in between the diameters of C2 H2 (3.3 Å) and C2 H4 (4.2 Å) molecules, leading to an efficient separation of the C2 H2 /C2 H4 mixtures by the sieving effect. The practical separation performance of C2 H2 /C2 H4 was confirmed by the dynamic breakthrough experiments. Moreover, the high stability enables the adsorption capacity of the Zn-MOF to C2 H2 , which can be maintained under a wide range of pH (1-13). Molecular simulations were also performed to identify the different C2 H2 - and C2 H4 -binding sites in Zn-MOF.