Andreas Schaate

Bio: Andreas Schaate is an academic researcher from Leibniz University of Hanover. The author has contributed to research in topics: Metal-organic framework & Materials science. The author has an hindex of 12, co-authored 17 publications receiving 1768 citations.

Modulated Synthesis of Zr‐Based Metal–Organic Frameworks: From Nano to Single Crystals

Abstract: We present an investigation on the influence of benzoic acid, acetic acid, and water on the syntheses of the Zr-based metal-organic frameworks Zr-bdc (UiO-66), Zr-bdc-NH(2) (UiO-66-NH(2)), Zr-bpdc (UiO-67), and Zr-tpdc-NH(2) (UiO-68-NH(2)) (H(2) bdc: terephthalic acid, H(2) bpdc: biphenyl-4,4'-dicarboxylic acid, H(2) tpdc: terphenyl-4,4''-dicarboxylic acid). By varying the amount of benzoic or acetic acid, the synthesis of Zr-bdc can be modulated. With increasing concentration of the modulator, the products change from intergrown to individual crystals, the size of which can be tuned. Addition of benzoic acid also affects the size and morphology of Zr-bpdc and, additionally, makes the synthesis of Zr-bpdc highly reproducible. The control of crystal and particle size is proven by powder XRD, SEM and dynamic light scattering (DLS) measurements. Thermogravimetric analysis (TGA) and Ar sorption experiments show that the materials from modulated syntheses can be activated and that they exhibit high specific surface areas. Water proved to be essential for the formation of well-ordered Zr-bdc-NH(2) . Zr-tpdc-NH(2), a material with a structure analogous to that of Zr-bdc and Zr-bpdc, but with the longer, functionalized linker 2'-amino-1,1':4',1''-terphenyl-4,4''-dicarboxylic acid, was obtained as single crystals. This allowed the first single-crystal structural analysis of a Zr-based metal-organic framework.

Porous interpenetrated zirconium-organic frameworks (PIZOFs): a chemically versatile family of metal-organic frameworks.

Abstract: We present the synthesis and characterization of porous interpenetrated zirconium-organic frameworks (PIZOFs), a new family of metal-organic frameworks obtained from ZrCl(4) and the rodlike dicarboxylic acids HO(2)C[PE-P(R(1),R(2))-EP]CO(2) H that consist of alternating phenylene (P) and ethynylene (E) units. The substituents R(1),R(2) were broadly varied (alkyl, O-alkyl, oligo(ethylene glycol)), including postsynthetically addressable substituents (amino, alkyne, furan). The PIZOF structure is highly tolerant towards the variation of R(1) and R(2). This together with the modular synthesis of the diacids offers a facile tuning of the chemical environment within the pores. The PIZOF structure was solved from single-crystal X-ray diffraction analysis. The PIZOFs are stable under ambient conditions. PIZOF-2, the PIZOF prepared from HO(2)C[PE-P(OMe,OMe)-EP]CO(2)H, served as a prototype to determine thermal stability and porosity. It is stable up to 325 °C in air as determined by using thermogravimetry and powder X-ray diffraction. Argon sorption isotherms on PIZOF-2 revealed a Brunauer-Emmett-Teller (BET) surface area of 1250 m(2) g(-1) and a total pore volume of 0.68 cm(3) g(-1).

A Novel Zr-Based Porous Coordination Polymer Containing Azobenzenedicarboxylate as a Linker

Abstract: A novel porous coordination polymer (PCP), Zr–abdc, composed of Zr-based secondary building units (SBUs), [Zr6O4(OH)4]12+, and 4,4′-azobenzenedicarboxylate (abdc2–) linkers, has been synthesized by a modulated synthetic approach. In accord with the twelve-fold connecting SBU, Zr–abdc has a topology similar to the PCP series UiO-66–UiO-68, which is proposed from single-crystal XRD and powder (P)XRD experiments. The linkers are strongly disordered, which made it impossible to determine the exact structure. The compound was further characterized by thermogravimetric analysis, scanning electron microscopy and Ar sorption measurements. Soxhlet extraction with ethanol instead of simple washing was helpful to remove guest molecules present in the pores after the synthesis. PXRD patterns measured at elevated temperatures show that a material stable up to 400 °C in air was obtained. After activation, it showed a specific surface area of 3000 m2 g–1 and a pore volume of 1.41 cm3 g–1.

A Calixarene-Based Metal-Organic Framework for Highly Selective NO2 Detection.

Abstract: A calixarene-based metal-organic framework (Zr-cal, [Zr6 O4 (OH)4 (FA)6 ]2 (cal)3 ], FA=formate, cal=1,3-alt-25,26,27,28-tetrakis[(carboxy)methoxy]calixarene) was synthesized and characterized by single-crystal X-ray diffraction. The three-dimensional framework is a 4,6-connected network of gar topology and exhibits two equal but nonintersecting three-dimensional pore systems. It has a specific BET surface area of 670 m2 g-1 , and the calixarene cavities are accessible through the pore systems. The exposed calixarenes can be used for the visual detection and encapsulation of NO2 through the formation of deeply colored charge-transfer complexes inside the MOF. The highly selective complexation was analyzed by UV/Vis and IR spectroscopy, and the stability of the material was confirmed by powder X-ray diffraction and 1 H NMR spectroscopy. Finally, the MOF was used as a sensor material in a home-made sensor cell and showed high sensitivity for NO2 .

Water Adsorption in Porous Metal–Organic Frameworks and Related Materials

Abstract: Water adsorption in porous materials is important for many applications such as dehumidification, thermal batteries, and delivery of drinking water in remote areas. In this study, we have identified three criteria for achieving high performing porous materials for water adsorption. These criteria deal with condensation pressure of water in the pores, uptake capacity, and recyclability and water stability of the material. In search of an excellently performing porous material, we have studied and compared the water adsorption properties of 23 materials, 20 of which are metal–organic frameworks (MOFs). Among the MOFs are 10 zirconium(IV) MOFs with a subset of these, MOF-801-SC (single crystal form), −802, −805, −806, −808, −812, and −841 reported for the first time. MOF-801-P (microcrystalline powder form) was reported earlier and studied here for its water adsorption properties. MOF-812 was only made and structurally characterized but not examined for water adsorption because it is a byproduct of MOF-841 s...

Stable Metal-Organic Frameworks: Design, Synthesis, and Applications.

Abstract: Metal-organic frameworks (MOFs) are an emerging class of porous materials with potential applications in gas storage, separations, catalysis, and chemical sensing. Despite numerous advantages, applications of many MOFs are ultimately limited by their stability under harsh conditions. Herein, the recent advances in the field of stable MOFs, covering the fundamental mechanisms of MOF stability, design, and synthesis of stable MOF architectures, and their latest applications are reviewed. First, key factors that affect MOF stability under certain chemical environments are introduced to guide the design of robust structures. This is followed by a short review of synthetic strategies of stable MOFs including modulated synthesis and postsynthetic modifications. Based on the fundamentals of MOF stability, stable MOFs are classified into two categories: high-valency metal-carboxylate frameworks and low-valency metal-azolate frameworks. Along this line, some representative stable MOFs are introduced, their structures are described, and their properties are briefly discussed. The expanded applications of stable MOFs in Lewis/Bronsted acid catalysis, redox catalysis, photocatalysis, electrocatalysis, gas storage, and sensing are highlighted. Overall, this review is expected to guide the design of stable MOFs by providing insights into existing structures, which could lead to the discovery and development of more advanced functional materials.