Phosphonate Metal–Organic Frameworks: A Novel Family of Semiconductors

Abstract

Herein, the first semiconducting and magnetic phosphonate metal–organic framework (MOF), TUB75, is reported, which contains a 1D inorganic building unit composed of a zigzag chain of corner‐sharing copper dimers. The solid‐state UV–vis spectrum of TUB75 reveals the existence of a narrow bandgap of 1.4 eV, which agrees well with the density functional theory (DFT)‐calculated bandgap of 1.77 eV. Single‐crystal conductivity measurements for different orientations of the individual crystals yield a range of conductances from 10−3 to 103 S m−1 at room temperature, pointing to the directional nature of the electrical conductivity in TUB75. Magnetization measurements show that TUB75 is composed of antiferromagnetically coupled copper dimer chains. Due to their rich structural chemistry and exceptionally high thermal/chemical stabilities, phosphonate MOFs like TUB75 may open new vistas in engineerable electrodes for supercapacitors.

A Nanotubular Metal–Organic Framework with a Narrow Bandgap from Extended Conjugation**

“…We have recently shown that the presence of phosphonic acids promotes electron delocalization in the one-dimensional inorganic buildingu nit (IBU) of the phosphonate MOF TUB75, whichi sc omposed of polyaromatic 1,4-naphthalenediphosphonic acid linkers and one-dimensional coppercontaining IBUs and has an arrow bandgapo f1 .4 eV. [16] To build upon this work, in this study,w eu sed ac onjugatedt etratopicl inker,H 8 and Gs tands for Gebze), whichh as au nique one-dimensional microporous tubular structure with av ery high geometric accessibles urface area of 1102 m 2 g À1 and low indirect bandgap of 1.90 eV. Due to the rich metal-binding modes of organophosphonates, the rational synthesis of phosphonate MOFsi nto predefined one-, two-, and three-dimensional frameworks has been ag reat challenge.…”

“…Metal–organic frameworks (MOFs) are microporous materials that contain well‐defined micropores composed of organic and inorganic surfaces [1–9] . They have been used in applications ranging from gas adsorption, sequestration of greenhouse gases, [10, 11] catalysis, [12, 13] magnetism, [14–17] drug delivery, [18, 19] cosmetics, [20] food packaging and transportation, [21, 22] proton conductive membranes, [23, 24] and electrical conduction [16, 25–28] . Although thousands of MOFs have been reported in the literature, the structural diversity of MOFs, MOF linker core geometries, and different metal‐binding functional groups have not been fully exploited yet.…”

“…In this direction, the phosphonic acid metal‐binding unit (R‐PO 3 2− ) containing phosphorus, which is a good conductor and has a negative charge that is evenly distributed over the three tetrahedronally oriented oxygen atoms, has shown great promise. We have recently shown that the presence of phosphonic acids promotes electron delocalization in the one‐dimensional inorganic building unit (IBU) of the phosphonate MOF TUB75, which is composed of polyaromatic 1,4‐naphthalenediphosphonic acid linkers and one‐dimensional copper‐containing IBUs and has a narrow bandgap of 1.4 eV [16] . To build upon this work, in this study, we used a conjugated tetratopic linker, H 8 ‐TPPA, to synthesize another narrow bandgap phosphonate MOF, namely [Ni(Cu‐H 4 TPPA)]⋅2 (CH 3 ) 2 NH 2 + ( GTUB‐4 , where TUB stands for Technische Universität Berlin and G stands for Gebze), which has a unique one‐dimensional microporous tubular structure with a very high geometric accessible surface area of 1102 m 2 g −1 and low indirect bandgap of 1.90 eV.…”

“…cosmetics, [20] food packaging and transportation, [21,22] proton conductive membranes, [23,24] and electrical conduction. [16,[25][26][27][28] Althought housands of MOFs have been reported in the literature, the structural diversity of MOFs,M OF linker core geometries, and different metal-binding functional groups have not been fully exploited yet. Recently,t wo new families of MOFs have emerged, whiche mploy phosphonic and phosphinic acids as metal-binding units, in contrastw ith the conventional MOFs that contain carboxylates and azolates.…”

Semiconductive microporous hydrogen-bonded organophosphonic acid frameworks

“…etal-organic frameworks (MOFs) emerged as revolutionary microporous materials at the beginning of the 21st century [1][2][3] . Owing to their well-ordered pores, which are surrounded by inorganic and organic components, MOFs have been used in a wide range of applications, such as gas storage/separation [4][5][6][7] , catalysis [8][9][10][11][12][13] , magnetism [14][15][16] , electric conductivity [17][18][19] , proton conductivity [20][21][22] , and drug delivery [23][24][25] . In parallel to MOF research, another closely related family of supramolecular architectures known as hydrogen-bonded organic frameworks (HOFs) has attracted immense interest in recent years [26][27][28] .…”