Probing Isoreticular Expansions in Phosphonate MOFs and their Applications

This review is divided into three different parts. In the introduction, the current applications of metal‐organic frameworks (MOFs) are shown. Furthermore, the overall stability, a comparison of phosphonate MOFs with carboxylate MOFs, the structural richness of phosphonate MOFs with the challenge in synthesis and different linker geometries is discussed. In the second part, several phosphonate MOFs with Y‐shaped planar, X‐shaped planar, and X‐shaped tetrahedral linker systems are described. The final part discusses different structures of inorganic building units (IBUs) with different metal atoms and a comparison of the formed MOF structures

Phosphonate Metal–Organic Frameworks: A Novel Family of Semiconductors

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.TU Berlin, Open-Access-Mittel - 202

Electrically Conductive Photoluminescent Porphyrin Phosphonate Metal-Organic Frameworks

Herein, the design and synthesis of a highly photoluminescent and electrically conductive metal–organic framework [Zn{Cu-p-H6TPPA}]⋅2 [(CH3)2NH] (designated as GTUB3), which is constructed using the 5,10,15,20-tetrakis [p-phenylphosphonic acid] porphyrin (p-H8TPPA) organic linker, is reported. The bandgap of GTUB3 is measured to be 1.45 and 1.48 eV using diffuse reflectance spectroscopy and photoluminescence (PL) spectroscopy, respectively. The PL decay measurement yields a charge carrier lifetime of 40.6 ns. Impedance and DC measurements yield average electrical conductivities of 0.03 and 4 S m−1, respectively, making GTUB3 a rare example of an electrically conductive 3D metal–organic framework. Thermogravimetric analysis reveals that the organic components of GTUB3 are stable up to 400 °C. Finally, its specific surface area and pore volume are calculated to be 622 m2 g−1 and 0.43 cm3 g−1, respectively, using grand canonical Monte Carlo. Owing to its porosity and high electrical conductivity, GTUB3 may be used as a low-cost electrode material in next generation of supercapacitors, while its low bandgap and high photoluminescence make it a promising material for optoelectronic applications

Coordination-Induced Band Gap Reduction in a Metal-Organic Framework

Herein, we report on the synthesis of a microporous, three-dimensional phosphonate metal-organic framework (MOF) with the composition Cu3 (H5 -MTPPA)2  ⋅ 2 NMP (H8 -MTPPA=methane tetra-p-phenylphosphonic acid and NMP=N-methyl-2-pyrrolidone). This MOF, termed TUB1, has a unique one-dimensional inorganic building unit composed of square planar and distorted trigonal bipyramidal copper atoms. It possesses a (calculated) BET surface area of 766.2 m2 /g after removal of the solvents from the voids. The Tauc plot for TUB1 yields indirect and direct band gaps of 2.4 eV and 2.7 eV, respectively. DFT calculations reveal the existence of two spin-dependent gaps of 2.60 eV and 0.48 eV for the alpha and beta spins, respectively, with the lowest unoccupied crystal orbital for both gaps predominantly residing on the square planar copper atoms. The projected density of states suggests that the presence of the square planar copper atoms reduces the overall band gap of TUB1, as the beta-gap for the trigonal bipyramidal copper atoms is 3.72 eV

A 3D Cu‐Naphthalene‐Phosphonate Metal–Organic Framework with Ultra‐High Electrical Conductivity

A conductive phosphonate metal–organic framework (MOF), [{Cu(H2O)}(2,6‐NDPA)0.5] (NDPA = naphthalenediphosphonic acid), which contains a 2D inorganic building unit (IBU) comprised of a continuous edge‐sharing sheet of copper phosphonate polyhedra is reported. The 2D IBUs are connected to each other via polyaromatic 2,6‐NDPA's, forming a 3D pillared‐layered MOF structure. This MOF, known as TUB40, has a narrow band gap of 1.42 eV, a record high average electrical conductance of 2 × 102 S m−1 at room temperature based on single‐crystal conductivity measurements, and an electrical conductance of 142 S m−1 based on a pellet measurement. Density functional theory (DFT) calculations reveal that the conductivity is due to an excitation from the highest occupied molecular orbital on the naphthalene‐building unit to the lowest unoccupied molecular orbital on the copper atoms. Temperature‐dependent magnetization measurements show that the copper atoms are antiferromagnetically coupled at very low temperatures, which is also confirmed by the DFT calculations. Due to its high conductance and thermal/chemical stability, TUB40 may prove useful as an electrode material in supercapacitors.TU Berlin, Open-Access-Mittel – 202

Semiconductive microporous hydrogen-bonded organophosphonic acid frameworks

Herein, we report a semiconductive, proton-conductive, microporous hydrogen-bonded organic framework (HOF) derived from phenylphosphonic acid and 5,10,15,20‐tetrakis[p‐phenylphosphonic acid] porphyrin (GTUB5). The structure of GTUB5 was characterized using single crystal X-ray diffraction. A narrow band gap of 1.56 eV was extracted from a UV-Vis spectrum of pure GTUB5 crystals, in excellent agreement with the 1.65 eV band gap obtained from DFT calculations. The same band gap was also measured for GTUB5 in DMSO. The proton conductivity of GTUB5 was measured to be 3.00 × 10−6 S cm−1 at 75 °C and 75% relative humidity. The surface area was estimated to be 422 m2 g−1 from grand canonical Monte Carlo simulations. XRD showed that GTUB5 is thermally stable under relative humidities of up to 90% at 90 °C. These findings pave the way for a new family of organic, microporous, and semiconducting materials with high surface areas and high thermal stabilities.DFG, 414044773, Open Access Publizieren 2019 - 2020 / Technische Universität Berli

Phosphonate Metal-Organic Frameworks: A Novel Family of Semiconductors

Herein is reported the first semiconducting and magnetic phosphonate metal-organic framework (MOF), TUB75, which contains a one-dimensional inorganic building unit composed of a zig-zag chain of corner-sharing copper dimers. The solid-state UV-Vis spectrum of TUB75 reveals the existence of a narrow band gap of 1.4 eV, which agrees well with the 1.77 eV one obtained from DFT calculations. 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. </p

A New Family of Layered Metal-Organic Semiconductors: Cu/V-Organophosphonates

Herein, we report the design and synthesis of a layered redox-active, antiferromagnetic metal organic semiconductor crystals with the chemical formula [Cu(H2O)2V(µ-O)(PPA)2] (where PPA is phenylphosphonate). The crystal structure of [Cu(H2O)2V(µ-O)(PPA)2] shows that the metal phosphonate layers are separated by phenyl groups of the phenyl phosphonate linker. Tauc plotting of diffuse reflectance spectra indicates that [Cu(H2O)2V(µ-O)(PPA)2] has an indirect band gap of 2.19 eV. Photoluminescence (PL) spectra indicate a complex landscape of energy states with PL peaks at 1.8 and 2.2 eV. [Cu(H2O)2V(µ-O)(PPA)2] has estimated hybrid ionic and electronic conductivity values between 0.13 and 0.6 S m−1. Temperature-dependent magnetization measurements show that [Cu(H2O)2V(µ-O)(PPA)2] exhibits short range antiferromagnetic order between Cu(II) and V(IV) ions. [Cu(H2O)2V(µ-O)(PPA)2] is also photoluminescent with photoluminescence quantum yield of 0.02%. [Cu(H2O)2V(µ-O)(PPA)2] shows high electrochemical, and thermal stability

High Electrical Conductivity in Three-Dimensional Porphyrin-Phosphonate Metal Organic-Frameworks

Herein, we report the design and synthesis of a highly electrically conductive and microporous three-dimensional zinc-phosphonate metal-organic framework [Zn(Cu-p-H4TPPA)] ⋅2 (CH3)2NH2+ (designated as GTUB3), constructed using the 5,10,15,20‐tetrakis [p‐phenylphosphonic acid] porphyrin (p-H8TPPA) organic linker. GTUB3 has an indirect band gap of 1.64 eV and a high average electrical conductivity of 4 S/m, making it a rare example of an electrically conductive zinc metal-organic framework. The N2-accessible geometric surface area of GTUB3, as predicted by molecular simulations, is 671 m2/g. Owing to its simple, high-yield synthesis at low temperatures, porosity, and electrical conductivity, GTUB3 may be used as a low-cost electrode material in next generation phosphonate-supercapacitors. </p