Fabrication of a Luminescence-Silent System Based on a Post-Synthetic Modification Cd-MOFs: A Highly Selective and Sensitive Turn-on Luminescent Probe for Ascorbic Acid Detection

Abstract

A unique three-dimensional luminescent metal–organic framework (Cd-MOFs), [Cd­(tpbpc)2]·2H2O·DMF (Htpbpc = 4′-[4,2′;6′,4″]-terpyridin-4′-yl-biphenyl-4-carboxylic acid; DMF = dimethylformamide), was synthesized and structurally characterized; it exhibits excellent luminescent property and structural stability in aqueous solutions. Interestingly, an unparalleled luminescence-silent system CrO4 2–@Cd-MOFs was successfully fabricated by postsynthetic modification of metal–organic frameworks. This luminescence-silent system represents a highly selective and sensitive turn-on luminescent responding to ascorbic acid. First, this advanced fluorescent sensor displays excellent performance for CrO4 2– ions with a quenching of fluorescence intensity originating from fluorescence resonance energy transfer (FRET) mechanism. What’s more, the fluorescent intensity of CrO4 2–@Cd-MOFs system can be recovered (turn-on) for sensing ascorbic acid because of the elimination of FRET process. Such a novel fabrication strategy should offer the guidance to develop various MOFs-implicated luminescence-silent systems as “turn-on” sensors for detection of specific chemicals.

Post‐Synthetic Modification of Metal–Organic Frameworks Toward Applications

“…The ligand‐based blue fluorescence is quenched by the guest molecules by fluorescence resonance energy transfer (FRET) mechanism and is recovered by the addition of ascorbic acid thereby acting as a selective and sensitive detector for the same. The novel method is a promising one to create such luminescent‐silent MOF systems as “turn‐on sensors.” [ 110 ] A ship‐in‐a‐bottle approach was employed by replacing MeNH 2 + ions by the metal ions in the first step and consecutively attaching functional molecules to the metal ions. This opened a new pathway for the inclusion of the guest molecule in the MOF pores beyond the pore window barrier.…”

“…FRET has a significant decrease of a donor, which of fluorescent intensity has risen, and the fluorescent color was recovered from dark to blue of CrO 4 2− @Cd‐MOFs. [ 110 ]…”

Isomers of Terpyridine as Ligands in Coordination Polymers and Networks Containing Zinc(II) and Cadmium(II)

“…Interestingly, {Cd 2 (O 2 C) 4 } units assemble ( Figure 34 a) and bear a resemblance to the 8-connecting dizinc nodes in [Zn( 33 ) 2 ] n ( Figure 34 b, and see also Figure 22 b). The 3D-network in [Cd( 33 ) 2 ] n · n DMF·2 n H 2 O is described by the authors as having a topological point symbol of {3 3 .4 7 .5 8 .6} [ 94 ]. A comparison of the structure of [Cd( 33 ) 2 ] n · n DMF·2 n H 2 O (CSD refcode BOBRIW) with that of [Zn( 33 ) 2 ] n (refcode TEZJOA) reveals that both compounds crystallize in the monoclinic space group P 2 1 / c with similar cell dimensions ( a = 21.8088(7), b = 10.3071(3), c = 29.9710(12) Å, β = 126.602(2)° for [Cd( 33 ) 2 ] n · n DMF·2 n H 2 O, and a = 21.5531(7), b = 10.2884(4), c = 29.7127(12) Å, β = 126.180(2)° for [Zn( 33 ) 2 ] n ) consistent with very similar assemblies.…”

“…A comparison of the structure of [Cd( 33 ) 2 ] n · n DMF·2 n H 2 O (CSD refcode BOBRIW) with that of [Zn( 33 ) 2 ] n (refcode TEZJOA) reveals that both compounds crystallize in the monoclinic space group P 2 1 / c with similar cell dimensions ( a = 21.8088(7), b = 10.3071(3), c = 29.9710(12) Å, β = 126.602(2)° for [Cd( 33 ) 2 ] n · n DMF·2 n H 2 O, and a = 21.5531(7), b = 10.2884(4), c = 29.7127(12) Å, β = 126.180(2)° for [Zn( 33 ) 2 ] n ) consistent with very similar assemblies. [Cd( 33 ) 2 ] n was shown to be a selective and very sensitive luminescent probe to detect ascorbic acid [ 94 ]. The dicarboxylic acid H 2 37 forms single crystals of [Cd( 37 )(OH 2 )] n · n MeCN·2 n H 2 O when reacted with H 2 37 under solvothermal conditions.…”

Terpyridine‐Based 3D Metal–Organic‐Frameworks: A Structure–Property Correlation

“…Although significant progress has been made in recent years in the design of 3D tpy‐MOFs and many applications have been studied extensively, there is still plenty of room available for further development. It is still a challenge to build a highly porous framework with 4′‐phenyl terpyridine derivatives [48] . From the MOF‐based sensing perspective, these frameworks have been explored only for the qualitative detection/encapsulation of analytes, whereas the quantitative efficiency in terms of analyte separation still needs to be explored.…”