Christopher A. Trickett

Definitive Molecular Level Characterization of Defects in UiO‐66 Crystals

The identification and characterization of defects, on the molecular level, in metal-organic frameworks (MOFs) remain a challenge. With the extensive use of single-crystal X-ray diffraction (SXRD), the missing linker defects in the zirconium-based MOF UiO-66, Zr6 O4 (OH)4 (C8 H4 O4 )6 , have been identified as water molecules coordinated directly to the zirconium centers. Charge balancing is achieved by hydroxide anions, which are hydrogen bonded within the pores of the framework. Furthermore, the precise nature of the defects and their concentration can be manipulated by altering the starting materials, synthesis conditions, and post-synthetic modifications.

Three-Dimensional Metal-Catecholate Frameworks and Their Ultrahigh Proton Conductivity

A series of three-dimensional (3D) extended metal catecholates (M-CATs) was synthesized by combining the appropriate metal salt and the hexatopic catecholate linker, H6THO (THO(6-) = triphenylene-2,3,6,7,10,11-hexakis(olate)) to give Fe(THO)·Fe(SO4) (DMA)3, Fe-CAT-5, Ti(THO)·(DMA)2, Ti-CAT-5, and V(THO)·(DMA)2, V-CAT-5 (where DMA = dimethylammonium). Their structures are based on the srs topology and are either a 2-fold interpenetrated (Fe-CAT-5 and Ti-CAT-5) or noninterpenetrated (V-CAT-5) porous anionic framework. These examples are among the first catecholate-based 3D frameworks. The single crystal X-ray diffraction structure of the Fe-CAT-5 shows bound sulfate ligands with DMA guests residing in the pores as counterions, and thus ideally suited for proton conductivity. Accordingly, Fe-CAT-5 exhibits ultrahigh proton conductivity (5.0 × 10(-2) S cm(-1)) at 98% relative humidity (RH) and 25 °C. The coexistence of sulfate and DMA ions within the pores play an important role in proton conductivity as also evidenced by the lower conductivity values found for Ti-CAT-5 (8.2 × 10(-4) S cm(-1) at 98% RH and 25 °C), whose structure only contained DMA guests.

Two Principles of Reticular Chemistry Uncovered in a Metal–Organic Framework of Heterotritopic Linkers and Infinite Secondary Building Units

Structural diversity of metal-organic frameworks (MOFs) has been largely limited to linkers with at most two different types of coordinating groups. MOFs constructed from linkers with three or more nonidentical coordinating groups have not been explored. Here, we report a robust and porous crystalline MOF, Zn3(PBSP)2 or MOF-910, constructed from a novel linker PBSP (phenylyne-1-benzoate, 3-benzosemiquinonate, 5-oxidopyridine) bearing three distinct types of coordinative functionality. The MOF adopts a complex and previously unreported topology termed tto. Our study suggests that simple, symmetric linkers are not a necessity for formation of crystalline extended structures and that new, more complex topologies are attainable with irregular, heterotopic linkers. This work illustrates two principles of reticular chemistry: first, selectivity for helical over straight rod secondary building units (SBUs) is achievable with polyheterotopic linkers, and second, the pitch of the resulting helical SBUs may be fine-tuned based on the metrics of the polyheterotopic linker.

Principles of Designing Extra-Large Pore Openings and Cages in Zeolitic Imidazolate Frameworks

We report three design principles for obtaining extra-large pore openings and cages in the metal-organic analogues of inorganic zeolites, zeolitic imidazolate frameworks (ZIFs). Accordingly, we prepared a series of 15 ZIFs, members of which have the largest pore opening (22.5 Å) and the largest cage size (45.8 Å) known for all porous tetrahedral structures. The key parameter allowing us to access these exceptional ZIFs is what we define as the steric index (δ), which is related to the size and shape of the imidazolate linkers employed in the synthesis. The three principles are based on using multiple linkers with specific range and ratios of δ to control the size of rings and cages from small to large, and therefore are universally applicable to all existing ZIFs. The ZIF with the largest cage size (ZIF-412) shows the best selectivity of porous materials tested toward removal of octane and p-xylene from humid air.

A Synthetic Route for Crystals of Woven Structures, Uniform Nanocrystals, and Thin Films of Imine Covalent Organic Frameworks

Developing synthetic methodology to crystallize extended covalent structures has been an important pursuit of reticular chemistry. Here, we report a homogeneous synthetic route for imine covalent organic frameworks (COFs) where crystallites emerge from clear solutions without forming amorphous polyimine precipitates. The key feature of this route is the utilization of tert-butyloxycarbonyl group protected amine building blocks, which are deprotected in situ and gradually nucleate the crystalline framework. We demonstrate the utility of this approach by crystallizing a woven covalent organic framework (COF-112), in which covalent organic threads are interlaced to form a three-dimensional woven framework. The homogeneous imine COF synthesis also enabled the control of nucleation and crystal growth leading to uniform nanocrystals, through microwave-assisted reactions, and facile preparation of oriented thin films.

Calcium l-Lactate Frameworks as Naturally Degradable Carriers for Pesticides

Two porous, chiral metal-organic frameworks (MOFs), Ca14(l-lactate)20(acetate)8(C2H5OH)(H2O) (MOF-1201) and Ca6(l-lactate)3(acetate)9(H2O) (MOF-1203), are constructed from Ca2+ ions and l-lactate [CH3CH(OH)COO-], where Ca2+ ions are bridged by the carboxylate and hydroxyl groups of lactate and the carboxylate group of acetate to give a three-dimensional arrangement of Ca(-COO, -OH) polyhedra supporting one-dimensional pores with apertures and internal diameters of 7.8 and 9.6 Å (MOF-1201) and 4.6 and 5.6 Å (MOF-1203), respectively. These MOFs represent the first examples of extended porous structures based on Ca2+ and lactate. They show permanent porosity of 430 and 160 m2 g-1, respectively, and can encapsulate an agriculturally important fumigant, cis-1,3-dichloropropene. MOF-1201 shows a 100 times lower release rate compared with liquid cis-1,3-dichloropropene under the same test conditions (25 °C, air flow rate of 1 cm3 min-1). The hydrolysis of MOF-1201 in water makes it the first example of a degradable porous solid carrier for such fumigants.

A complex metal-organic framework catalyst for microwave-assisted radical polymerization

Metal-organic frameworks (MOFs) have emerged as promising materials for use in practical applications of renewable energy, water harvesting, and catalytic transformation. Here we report the design of a highly porous MOF, termed MOF-907. Single crystal X-ray diffraction analysis, in combination with topological deconstruction, revealed a MOF based on trigonal prismatic secondary building units linked together by triangular and linear units to form a previously unseen net (nha) with minimal transitivity, which is rational for these constituent building units. The catalytic properties of MOF-907 for the microwave-assisted radical polymerization of methyl methacrylate were demonstrated. MOF-907 produced a poly methyl methacrylate product in a short reaction time (30 min) with high yield (98%), high molecular weight (20,680 g mol−1), and low polydispersity (1.23).Metal-organic frameworks are attractive candidates as catalyst materials. Here, the authors report a highly symmetric hierarchical framework with a rare nha net topology catalyzing microwave-assisted radical polymerization of methyl methacrylate in high yields.

CCDC 1525655: Experimental Crystal Structure Determination

Related Article: Jingjing Yang, Yue-Biao Zhang, Qi Liu, Christopher A. Trickett, Enrique Gutierrez-Puebla, M. Angeles Monge, Hengjiang Cong, Abdulrahman Aldossary, Hexiang Deng, and Omar M. Yaghi|2017|J.Am.Chem.Soc.|139|6448|doi:10.1021/jacs.7b02272

CCDC 1423169: Experimental Crystal Structure Determination

Related Article: Jingjing Yang, Yue-Biao Zhang, Qi Liu, Christopher A. Trickett, Enrique Gutierrez-Puebla, M. Angeles Monge, Hengjiang Cong, Abdulrahman Aldossary, Hexiang Deng, and Omar M. Yaghi|2017|J.Am.Chem.Soc.|139|6448|doi:10.1021/jacs.7b02272

CCDC 1423175: Experimental Crystal Structure Determination

Related Article: Jingjing Yang, Yue-Biao Zhang, Qi Liu, Christopher A. Trickett, Enrique Gutierrez-Puebla, M. Angeles Monge, Hengjiang Cong, Abdulrahman Aldossary, Hexiang Deng, and Omar M. Yaghi|2017|J.Am.Chem.Soc.|139|6448|doi:10.1021/jacs.7b02272