R-Substituent induced structural diversity, synergistic effect and highly selective luminescence sensing for Fe3+ detection by post-synthetically modified Cd-MOFs. Issue 22 (22nd May 2020) - Liu, Qing
Abstract : Six Cd2 (OCO)2 cluster based MOFs involving 5-substituted isophthalic acid and n -TPT ligands have been characterized. Cd-MOF- 4 can be functionalized by Eu 3+ ions by PSMs, which shows highly selective and sensitive to Fe 3+ ion in aqueous solution. Abstract : The self-assembly of 5-substituted isophthalic acid (R-H2 BDC, R = H, NO2, Me, OH and t Bu), Cd II ions and 2, 4, 6-tris(3-pyridyl)-1, 3, 5-triazine (3-TPT) or 2, 4, 6-tris(4-pyridyl)-1, 3, 5-triazine (4-TPT) under solvothermal conditions yields six Cd-MOFs: {[Cd(BDC)(4-TPT)]·1.5H2 O} n (Cd-MOF- 1 ), {[Cd(NO2 -BDC)(4-TPT)]·2H2 O} n (Cd-MOF- 2 ), {[Cd(Me-BDC)(4-TPT)]·2H2 O} n (Cd-MOF- 3 ), {[Cd(OH-BDC)(4-TPT)]·2.5H2 O} n (Cd-MOF- 4 ), {[Cd( t Bu-BDC)(4-TPT)2/3 ]·DMF} n (Cd-MOF- 5 ), and {[Cd(BDC)(3-TPT)2/3 ]·3H2 O} n (Cd-MOF- 6 ), (where H2 BDC = isophthalic acid, NO2 -BDC = 5-nitroisophthalic acid, Me-BDC = 5-methylisophthalic acid, OH-BDC = 5-hydroxyisophthalic acid, t Bu-BDC = 5- tert -butylisophthalic acid, 3-TPT = 2, 4, 6-tris(3-pyridyl)-1, 3, 5-triazine and 4-TPT = 2, 4, 6-tris(4-pyridyl)-1, 3, 5-triazine). All the compounds are constructed from dimeric Cd2 (OCO)2 units, connected by mixed R-H2 BDC and n -TPT ligands into three-dimensional frameworks. Cd-MOF- 1, 2 and 3 are isostructural, in which the Cd2 (OCO)2 units are bridged into 1D chains extending along the [1 1 0] and [−1 1 0] directions, respectively, and are then further interlinked by 4-TPT ligands into three-dimensional networks with a CdS net topology. Cd-MOF- 4 exhibits a three-dimensional framework with a pcu topology, in which the dimeric Cd2 (OCO)2 units are firstly connected into two-dimensional Cd(OH-BDC) n sheets, and further "pillared" by 4-TPT into a three-dimensional network. In Cd-MOF- 5 and 6, the Cd2 (OCO)2 units are firstly linked into a three-dimensional NbO net by t Bu-BDC/BDC ligands, which are further accommodated by the size-matching trigonal 3-TPT/4-TPT ligands into a novel (3, 8)-connected three-dimensional net. Interestingly, via the synergistic effect of open hydroxyl and pyridyl groups, Cd-MOF- 4 can be functionalized by Eu 3+ ions by post-synthetic modification, and the resulting 0.001Eu 3+ @Cd-MOF- 4 phosphor serves as a highly selective and sensitive probe for detection and recognition of Fe 3+ ions through the luminescence quenching effect in aqueous solution.