Molecular Vise Approach to Create Metal‐Binding Sites in MOFs and Detection of Biomarkers

Abstract

We report a new approach to create metal-binding site in a series of metal-organic frameworks (MOFs), where tetratopic carboxylate linker, 4',4'',4''',4''''-methanetetrayltetrabiphenyl-4-carboxylic acid, is partially replaced by a tritopic carboxylate linker, tris(4-carboxybiphenyl)amine, in combination with monotopic linkers, formic acid, trifluoroacetic acid, benzoic acid, isonicotinic acid, 4-chlorobenzoic acid, and 4-nitrobenzoic acid, respectively. The distance between these paired-up linkers can be precisely controlled, ranging from 5.4 to 10.8 Å, where a variety of metals, Mg , Al , Cr , Mn , Fe , Co , Ni , Cu , Zn , Ag , Cd and Pb , can be placed in. The distribution of these metal-binding sites across a single crystal is visualized by 3D tomography of laser scanning confocal microscopy with a resolution of 10 nm. The binding affinity between the metal and its binding-site in MOF can be varied in a large range (observed binding constants, K from 1.56×10 to 1.70×10 L mol ), in aqueous solution. The fluorescence of these crystals can be used to detect biomarkers, such as cysteine, homocysteine and glutathione, with ultrahigh sensitivity and without the interference of urine, through the dissociation of metal ions from their binding sites.

Facile and reversible digestion and regeneration of zirconium-based metal-organic frameworks

“…etal-organic frameworks (MOFs) are emerging porous materials that have shown promise in cancer therapy 1,2 , catalysis [3][4][5] , chemical sensing 6,7 , and energy-storage applications [8][9][10][11] , including as electrodes, [12][13][14][15][16][17][18][19][20] separators 21,22 , and electrolytes 23 , due to their high surface area 24 , abundant ordered pores 25 , and tailored pore environment 26 . Zirconium-based MOFs (Zr-MOFs) are promising framework materials for practical applications because of their higher thermal and chemical stability compared with other MOFs 27,28 .…”

Fluorescent “Turn‐on” Sensing Based on Metal–Organic Frameworks (MOFs)

“…Deng and co‐workers in their recent report have introduced a novel metalation strategy inside the MOFs by staging the metal ions between two rigid ligands in a vise like manner . They established the molecular vise approach with MOF PCN‐521, fabricated of tetratopic organic ligands (4′,4′′,4′′′,4′′′′‐methanetetrayltetrabiphenyl‐4‐carboxylic acid, MTBC).…”

“…[52] Deng and co-workersi nt heir recent report have introduced an ovel metalation strategy inside the MOFs by staging the metal ions between two rigid ligands in av ise like manner. [53] They established the molecular vise approach withM OF PCN-521, fabricated of tetratopic organic ligands (4',4'',4''',4''''-methanetetrayltetrabiphenyl-4-carboxylic acid, MTBC). The tetratopic ligand was partly replaced by two tritopic ligand,t ris(4-carboxybiphenyl) amine (TBPA) and a single monotopic ligand resulting the formation of MV-MOF (MVPCN-521-R).…”

Circumventing Wear and Tear of Adaptive Porous Materials

“…This is common to framework materials made of reversible linkage chemistry, where ligand substitution reactions or dynamic covalent chemistry can take place, as exemplified by replacing tetratopic carboxylate linker in PCN-521 by a tritopic linker, leaving an unconnected site. [23] Other than permanent disconnection, dynamic dissociation of building units can take place, facilitated by the temporary bonding of foreign ligands. It was revealed that the Zn 2+ ions in MOF-5 bind solvent molecules, thereby increasing their coordination number and dynamically dissociating from the framework even at low temperatures.…”