The unprecedented accumulation of anthropogenic carbon dioxide (CO2) in Earth’s atmosphere has been the cause of multiple aggravating global climate problems and posed severe challenges to our delicate ecosystem. With the entire society’s heavy reliance on fossil fuel combustion, it is of immediate importance to employ efficient and cost-effective CO2 capture techniques globally to control the emission and alleviate the already-emerging environmental problems. Whether capturing from point sources or directly capturing from the air, existing methods exhibit different advantages and disadvantages, and the central challenge is the reduction of the cost per unit capture of CO2, both in terms of energy and matter, which lays the fundament of their scalability and economic feasibility. We believe that the fundamental solution toward the next-generation CO2 capture solution is the use of chemical tools to develop sorbent materials with overall optimized performances, especially in terms of uptake capacity, selectivity, regeneration energy consumption, and stability, to allow for rapid, efficient capture and collection of CO2 from flue gas or air repeatedly over a long time. Chapter 1 summarized major classes of existing sorbent materials for post-combustion capture and direct air capture of CO2 based on chemical looping and cycling capture protocols, elaborating on their advantages and disadvantages in the above-mentioned aspects.The development of reticular chemistry has yielded powerful tools holding high potential in resolving this challenge. By linking judiciously designed molecular building blocks into predetermined crystalline structures through strong coordinative or covalent bonds, a vast variety of compounds including metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have been developed and studied. Their unique construct combines atomically well-defined structures, extensively exposed surfaces, and the ability to host unparalleled variabilities within one structure while retaining precise tunability. With these limitless possibilities, in this thesis, I focus on the development of stable framework structures toward the design and synthesis of effective amine-functionalized chemisorbents for scalable, cost-effective carbon capture sorbents. Chapter 2 presents the design and synthesis of a class of unsubstituted olefin-linked covalent organic framework, exemplified by COF-701. The central challenge lies in translating the small-molecular organic chemistry into COF linkage chemistry through solving the crystallization problem. I showed that COF-701 can be synthesized through acid catalyzed Aldol condensation reaction starting from molecular reactions. Isotope-labeling experiments using Fourier Transform Infrared Spectroscopy (FT-IR) and solid-state NMR proved the formation of the unsubstituted olefin linkage, which endowed the COF to maintain its crystallinity and composition in the presence of strong acid/base, organolithium reagents, and Lewis acids. Chapter 3 presents the development of a class of amine-functionalized chemisorbents for post-combustion capture through coordinatively functionalizing a Zr-based MOF with amino acids. The sorbent exhibited enhanced uptake of CO2 in the presence of water, which was further probed using solid-state NMR. It was identified that in the presence of humidity and abundance of CO2 (flue gas conditions), the framework uptakes CO2 into bicarbonate species, which can be removed with vacuum at room temperature. The MOF was subjected to a vacuum-swing adsorption process to capture and release CO2 from a simulated coal flue gas without observed capacity decrease. Chapter 4 includes the ongoing progress of developing the next generation chemisorbents for direct air capture using MOFs, which require higher reactivity, low energy requirements, and profound stability. The sorbent development was based on expanding the chemistry of base-stable Fe-hydroxamate MOFs and covalently functionalizing the framework with aliphatic amines, in an effort to withstand the basicity necessary for achieving abundant CO2 affinity for direct air capture. Chapter 5 provides the discoveries of covalently functionalizing stable COFs toward chemisorbents for CO2 capture from flue gas and air. Based on the chemistry established in Chapter 2, I discuss two approaches to introduce amine species into olefin-linked COFs — through pre-crystallization linker amination, and post-synthetic modification. Both directions are currently in progress, and the findings were summarized to discuss the advantages and disadvantages of both approaches. The strategy of functionalizing stable COFs for carbon capture opens up the possibilities to allow a much wider range of chemistry to be developed into the framework without being limited by the stability, which holds high promise for the achievement of the next level of overall optimization, and contribute to resolving the carbon capture challenge fundamentally.

Chapter 1. Introduction to the fundamentals of reticular chemistry, metal–organic frameworks and covalent organic frameworks.

Chapter 2. Covalent organic frameworks (COFs) are almost entirely based on reversible condensation reactions. This precludes their stability in the presence of water, especially under strongly acidic and basic conditions; simply put, they are prone to hydrolysis. Strategies such as linkage conversion and stabilizing the linkage through covalent functionalization of building units have been developed to overcome these shortcomings, but they require elaborate synthetic efforts to obtain the desired stability. Here, we report a synthetic strategy based on an irreversible nucleophilic aromatic substitution reaction (SNAr) for the synthesis of COFs. In this chapter, we report the synthesis of two new crystalline, porous COFs, termed COF-316 and 318, constructed from new dioxin linkages (C–O bond). For the first time, SNAr reaction has been translated into COF linkage chemistry. The resultant COFs have high chemical stability under both acidic and basic conditions. The utility of this approach is highlighted by two new post-synthetic modification reactions carried out on the COF-316 backbone necessitating extreme conditions, yielding two new functionalities, amide and amidoxime in COFs, which were inaccessible previously.

Chapter 3. Covalent organic frameworks (COFs) can be categorized into 2D and 3D topologies based on the number of vertices, edges, rings and tiles. While the majority of the COFs reported to date are 2D layered structures, there are only five possible 2D topologies with one kind of edge, and all the 2D COFs belong to these five or defected versions. Strategies such as mixing more than two kinds of linkers and desymmetrizing the linkers by changing the edge lengths or vertex angles have been developed to increase the structural diversity of COFs, but fundamentally the underlying topologies still remain limited to the five aforementioned structural types. In this chapter, we report a synthetic strategy for the synthesis of COFs with new topologies that have more than one kind of edge. Specifically, a new crystalline, porous COF, termed COF-346, based on imine linkage with a new tth topology was synthesized (topologies are denoted by unique lowercase bolded three-letter identifiers, same as below). For the first time, linkers with three different connectivity (3, 4 and 6-connected) have been incorporated into one COF by precisely chosen geometry and metrics of linkers. We also report two additional structurally related COFs termed COF-360, with a rare kgd (kagome dual lattice) topology, and COF-340, with a defected tth topology. This work serves to expand the scope of 2D COF structures and realize new strategies for increasing complexity of COFs by design.

Chapter 4. Fundamentally, it is known to be a challenge to use single elongated organic component for the construction of MOFs with ultrahigh porosity due to the limited solubility of large linkers and the propensity of framework interpenetrations. In addition, activation of such materials is rather difficult as the large pores are especially susceptible to collapse. In this chapter we report the synthesis, crystal structure, and porosity of four Zn4O(-COO)6-based MOFs with the nia-net (the same topology as NiAs) using triptycene-derived hexatopic linkers, termed MOF-2008, Zn4O(Trip-Ph), Trip-Ph = 2,3,6,7,14,15-hexakis(4-benzoate) triptycene, MOF-2011, Zn4O(TripMe-Ph), TripMe-Ph = 2,3,6,7,14,15-hexakis(4-benzoate)-9,10-dimethyl triptycene, MOF-2015, Zn4O(Trip-Naph), Trip-Naph = 2,3,6,7,14,15-hexakis(4-naphthoate) triptycene, and MOF-2020, Zn4O(Trip-Biph), Trip-Biph = 2,3,6,7,14,15-hexakis(4’-biphenylcarboxylate) triptycene. MOF-2020 retained ultrahigh porosity upon successful activation, demonstrating its structural integrity, and showed the highest BET surface area (6160 m2 g-1) and pore volume (3.05 cm3 g-1) among the series.

Chapter 5. Ultrahigh-capacity methane storage is essential for heavy-duty vehicles fueled by methane. However, it s still rare for MOFs to achieve the Department of Energy (DOE) target for methane storage systems at 35 or 65 bar. In this chapter, we report the high pressure methane adsorption results based on the four NiAs-typed MOFs developed in the previous chapter. MOF-2008 and -2020 exhibited exceptional volumetric and gravimetric methane working capacities, respectively. MOF-2008 has a volumetric working capacity of 271 cm3 cm-3 (from 5.8 to 200 bar at 298 K), representing a remarkable 27% improvement compared to the compressed natural gas (CNG). MOF-2020 has a gravimetric working capacity of 0.666 g g-1, which is the highest among MOFs, to our certain knowledge, surpassing the current DOE target (0.5 g g-1) by 33%.

Chapter 6. Conclusion and outlook in reticular chemistry.

Metal-organic frameworks (MOFs) are porous, crystalline, extended structures made by linking inorganic and organic molecular building blocks together through strong coordination bonds. Due to their high surface areas, pore volumes, and the possibility of decorating them with a great variety of chemical functionalities through the judicious choice and design of their inorganic joints and organic struts, MOFs have been studied extensively and found useful in widespread industrial applications, such as gas storage, separation, and catalysis.

The design and synthesis of new MOFs with desirable properties and functions is a central theme in MOF chemistry. Generally, the structural design of MOFs is realized by a reticular synthesis approach, whereby the metal-based nodes and rigid organic linkers have predetermined geometries. However, when it comes to MOFs with flexible coordination geometries, it can become challenging to successfully guide the synthesis.

The work herein describes my Ph.D. research, dealing with the structural design of two important subclasses of MOFs, zeolitic imidazolate frameworks (ZIFs) and calcium-based environmentally friendly MOFs. Due to the structural unpredictability arising from the flexible coordinative behavior of the metal centers and organic linkers, the development of both classes of materials has so far relied heavily on synthetic “trial and error”, which has greatly limited their structural diversities. The work presented here shows that such challenges can be addressed by the synergistic assembly of linkers with different functionalities (mixed-linker approach). Following this strategy, fifteen new porous ZIF structures (amongst which structures presenting the largest cage and aperture reported for ZIFs), and two new porous calcium lactate frameworks were created. Furthermore, this work allowed the identification and establishment of three general principles for the guided structural design of ZIFs.

Chapter 1 introduces the concept, synthesis, characterization, and classification of MOFs. Then the importance and existing approaches for structural design are summarized. Finaly, the structure-function relationship is discussed to address the potentials of MOF materials in practical industrial applications.

Chapter 2 reports the synthesis and characterization of a series of ZIFs with ultra-large pores and aperture sizes via the mixed-linker approach. The synthesis of fifteen new ZIFs (ZIF-303, -360, -365, -376, -386, -408, -410, -486, -412, -413, -414, -516, -586, -615, and -725) is presented. Members of this list represent ZIFs with the largest pore sizes and aperture sizes (ZIF-412 and ZIF-516, -586, -615, -725) reported so far. Morevoer, a tertiary combination of linkers with different functionalities is reported for the first time in these new structures.

Chapter 3 builds upon the work of Chapter 3 and addresses the desire to uncover general synthetic principles to guide the synthesis of ZIFs. It begins with the analysis of relationship between the imidazolate starting material and framework structure based on the fifteen new ZIFs presented in Chapter 2. The ring in the ZIF structure is identified as the bridge, and the mixed imidazolate approach is the key to tune the ring size and composition. Based on these analyses, three general principles are identified which are applicable to the whole class of ZIF materials.

Chapter 4 switches focus from the previous chapters, and explores the use of a mixed-linker approach in another subfield of MOFs: calcium-based MOFs. The successful implementation of the mixed-linker approach in the ZIF synthesis encouraged us to explore similar synthetic challenges in other fields. In this chapter, the environmentally-friendly calcium-based MOFs are selected as topic of investigation. Using a combination of naturally existing lactate and acetate linkers, the first two examples of porous of calcium lactate frameworks are synthesized and presented. I demonstrate that both of these linkers are essential to the successful formation of the final structure.

Chapter 5 presents potential applications of the newly-made MOFs described in the previous chapters. A particular attention is paid to environmental applications benefiting from the structural and componential characters of the MOFs. The hydrophobic large-pore ZIF is demonstrated to be highly efficient for air purification through the removal of volatile organic compounds, and the calcium-based MOF, exhibiting an environmentally-friendly composition, is shown to be an effective pesticide carrier for agriculture purposes.

Chapter 6 is the final chapter of my thesis, in which I provide my humble thoughts and perspectives of the future development of the structural design of MOFs. MOFs are highly potential in real world applications, and the rational design of their structures and compositions, in order to meet the requirements for targeted applications, is the key to success.

The assembly of organic and inorganic building units into porous crystalline structures has given rise to metal-organic frameworks (MOFs). The wide variety of these building blocks has propelled the discovery of MOFs with new structures, topologies and chemical properties. In retrospect, MOFs itself can be used as a building unit for subsequent synthesis to impart functionalities for specific purposes. In this dissertation, I used MOFs as a building unit for functionalizing metal nanocrystals (NCs) and for post-synthetic modifications of their interior to synthesize metal complexes for heterogeneous catalysis and hydrogen storage.

Following this direction, a zirconium-based MOF, UiO-66, was used to encapsulate copper NCs to affect the catalytic activity of copper NC for CO2 hydrogenation to methanol. In this construct, a periodic array of zirconium oxide clusters is situated on the Cu surface resulting in high interfacial contact between copper NC and zirconium oxide clusters. We found that this catalyst is highly active and selective for the synthesis of methanol. Systematic investigations and X-ray photoelectron spectroscopy suggest the presence of the interaction between copper NC and zirconium oxide cluster at the interface, also known as strong–metal support interaction (SMSI), that leads to such catalytic performance.

We have used the same interaction to anchor a single atom of copper on the missing linker defect site of zirconium oxide clusters of UiO-66. The resulting catalyst is highly active for CO oxidation with high stability and selectivity for CO oxidation. In-situ X-ray absorption spectroscopy and in-situ infrared spectroscopy show that the single copper site remains isolated throughout the heat treatment under different gases including nitrogen and hydrogen even at 350 °C.

With regard to modifications of MOF interior, MOFs have a wide range of structures, topologies and chemical functionalities primed for creating a complexity akin to the active sites of enzymes. We employed this diversity to create an active site inspired by particulate methane monooxygenase (pMMO), an enzyme that oxidizes methane to methanol in nature with high activity and high selectivity. By judicious selection of MOF with desired geometric parameters, we used MOF-808 as a precursor for post-synthetic modifications to install ligands bearing imidazole units and metalation with Cu(I) in the presence of dioxygen. The catalysts show high selectivity for methane oxidation to methanol under isothermal conditions at 150 °C. Combined spectroscopies and density functional theory calculations reveal bis(-oxo) dicopper species as the active site of the catalysts.

Finally, we have employed the post-synthetic modification of MOFs to install metal sites functioning as hydrogen adsorption sites for gas storage purpose. In this work, IRMOF-74-III equipped with primary amines was functionalized to install metal-binding ligands including Schiff base and catecholate ligands. The MOFs were subsequently metalated with Ni(II) and tested for hydrogen adsorption properties.

Chapter 1: Anionic framework materials, including anionic metal–organic frameworks (MOFs) and anionic covalent organic frameworks (COFs), are promising candidates as solid-state electrolytes for next-generation lithium metal batteries. In contrast to charge-neutral framework materials, which serve only as porous supports for a liquid electrolyte, anionic framework materials also act as sources of lithium ions. Immobilization of anions onto the backbone of the framework makes lithium ion the predominant mobile species within the material, turning the material into a single ionic conductor. Strategies for developing anionic framework materials are summarized and technical details for proper characterization of the materials are discussed.

Chapter 2: A new anionic MOF, termed MOF-688, was synthesized by linking ditopic amino functionalized polyoxometalate [N(C4H9)4]3[MnMo6O18{(OCH2)3CNH2}2] with 4-connected tetrahedral tetrakis(4-formylphenyl)methane building units through imine condensation. The structure of MOF-688 was solved by single crystal X-ray diffraction. Lithium ions exchanged MOF-688 gives high ionic conductivity (3.4 × 10-4 S cm-1 at 20 °C), high lithium ion transference number (0.87), and low interfacial resistance (353 Ω) against metallic lithium. A prototype lithium metal battery constructed using MOF-688 as the solid electrolyte can be cycled at room temperature with a current density of 0.2 C.

Chapter 3: Porous MOF glasses can provide the opportunity of generating monoliths without grain boundaries, which is the mechanically fragile part of the pellet made from crystalline MOFs. MOF glasses with carboxylate linkage was synthesized by linking Ti16O16(OEt)32 and ditopic linker fumaric acid. The obtained MOF glass, termed Ti-Fum, showed a nitrogen BET surface area of 923 m2 g-1, nearly three times higher than Ti-BPA—the phenolate-linked MOF glass with the highest BET surface area reported previously. The formation of the linkage between Ti-oxo clusters and bridging carboxylate was verified by infrared. The structural integrity of discrete Ti-oxo clusters inside the MOF glass was evidenced by X-ray absorption near edge structure (XANES) and 17O magic angle spinning (MAS) NMR spectroscopy. Two additional carboxylic acid linkers were also used to demonstrate the modularity and versatility of this approach.

Chapter 4: Two strategies were employed to design and synthesize anionic COFs that adsorb water from air at low relative humidity. In the first strategy, the Povarov reaction between aryl imines and aryl alkynes was applied to COFs to convert the imine linkages into quinoline linkages while introducing carboxylates at the same time. In the second strategy, a sulfonate containing COF was synthesized directly by reacting 4,4',4'',4'''-(pyrene-1,3,6,8-tetrayl)tetrakis(2-hydroxybenzaldehyde) with ammonium 2,5-diaminobenzenesulfonate. The conversion was evaluated by infrared and elemental analysis, and the crystallinity of the COFs was confirmed by powder X-ray diffraction. Compared with the COFs without side chain, the COFs with anionic side chain showed significantly improved water uptake performance at low relative humidity.

Chapter 5: This chapter provides an outlook on anionic frameworks as solid-state electrolytes and water harvesters.

The development of metal-organic frameworks (MOFs) has experienced three main periods: (1) discovery of new structures; (2) structure design using the principles of reticular chemistry; and (3) study of these new materials in various applications. We are now in the third period as MOFs are extensively tested in a large number of potential applications, such as gas-storage and separation, catalysis, design of energy storage devices, drug delivery, and molecule sensing and recognition. The increasing applications of MOFs is raising the demand for the materials, therefore in this dissertation, I will focus on design and synthesis of new MOFs with high storage capacity for various gases including water, ammonia, and methane; and design and synthesis of MOF-based solid acids and the study of their liquid and vapor phase catalytic properties.

The strategy of material design targets practical applications. Thus, with different gas storage purposes in mind, different materials are proposed. In the first example, the need to capture water vapor at low humidity requires MOFs to exhibit pore filling or condensation of water into the pores at P/P0 < 0.1. Thus we have designed a small pore zirconium MOF, MOF-801, for this purpose. MOF-801 is shown to have high uptake of water, recyclability, and water stability. In the second example, the need to capture harmful ammonia gas requires MOFs with strong binding sites for the basic gas at low concentration. Thus we have designed and installed strongly acidic sites in a zirconium MOF, sulfated MOF-808, for this purpose. This sulfated MOF-808 is shown to take up 5.3 mmol ammonia per gram at P < 1.5 Torr, and 16.7 mmol ammonia at P = 760 Torr, one of the highest numbers for a MOF-based ammonia capture material. In the third example, high methane gas storage capacity at 80 bar was attempted using MOFs. This increase on the working capacity (between 5 and 80 bar) requires MOFs to have both high surface area and suitable pore sizes. For this purpose, we have designed zinc MOFs using organic linkers having delocalized π-electrons and with suitable pore metrics. The compound, MOF-905, shows 200 cm3 cm-3 working capacity between 5 and 80 bar, the highest of all zinc MOFs and is equivalent to the benchmark HKUST-1 compound.

With regard to the design and synthesis of MOF-based solid acids, three approaches have been proposed: (1) acidic functional groups bound to the organic linker; (2) acidic ligands bound to the inorganic cluster; and (3) acidic molecules encapsulated in MOF pores. While in the first approach, the acidity of the MOF is mostly determined by the acidity of the free acidic functional group, the latter two strategies provide for more interaction between the framework and the acidic groups, which is of great importance to understand the chemistry within the pores. A new type of MOF-based solid acid is demonstrated by the controllable sulfation of a zirconium MOF, MOF-808, on the inorganic cluster. The substitution of terminal formate groups in MOF-808 with sulfate groups has imparted strong acidity onto the sulfated MOF-808. The material has shown activity for acid catalyzed Friedel-Crafts acylation, esterification, isomerization, as well as the conversion of methylcyclopentane (MCP) into various hydrocarbons at 150-200 oC. Another MOF-based acid is synthesized by including phosphotungstic acid (PTA) into the large cages of MIL-101. Interestingly, we have found that the Brønsted acidity (originating from PTA) of the composite material is not directly proportional to the loading of PTA, but instead, it is not exhibited until certain loading of PTA is reached. This is explained by the level of protonation of PTA incorporated into the material, where the material with the highest loading, Pt/60PTA/MIL-101, is shown to effectively catalyze hydroisomerization of n-hexane at 250 oC.

Described in this dissertation is the designed synthesis and characterization of a new class of materials – woven crystalline covalent organic frameworks (COFs). Molecular building units are stitched together through strong bonds in a process termed reticular synthesis. In conjunction with metal-templated synthesis woven frameworks are obtained. The products of this reticulation are extended covalently linked one-dimensional (1D) organic molecules that mutually interweave at regular intervals to construct crystalline two- and three-dimensional (2D and 3D) architectures. The mechanical entanglement between the constituents (i.e. 1D chains) allows for large spatial deviations to take place without the breaking of covalent bonds, leading to unusual mechanical properties and ultimately to materials with exceptional resilience and dynamics.

In Chapter I, a general introduction of covalent organic frameworks (COFs) and their designed synthesis based on the fundamental concepts of reticular synthesis is given. Since the discovery of COFs in 2005, a plethora of COF structures with various structure types have been synthesized by reticulating judiciously selected building blocks of desirable connectivity and geometry. The structural tunability and crystallinity of COFs make them the ideal candidates for the synthetic realization of woven extended structures. The metal templation strategy, widely explored in the field of supramolecular chemistry, employs metal ions as templates to pre-organize organic linkers into desirable orientations, which can then be reticulated into woven extended frameworks. These metal ions also serve as the crossing points (points of registry) of the resultant woven threads, and upon demetaltion, the threads have high degrees of freedom to move about these points of registry without undoing the weaving.

Chapter II describes the implementation of the design strategy of COFs toward the successful synthesis of the first woven material, COF-505. A copper(I)-bisphenanthroline core, a well-established template in the field of supramolecular chemistry, was functionalized with aldehyde groups and used as a building block for COF synthesis. Specifically, the tetratopic and tetrahedrally-shaped complex was reacted with a linear ditopic benzidine (BZ) linker through reversible imine condensation to form a 3D crystalline framework, COF-505, of dia topology. The structure was determined with atomic precision, by a combined 3D electron diffraction tomography (3D-EDT) and powder X-ray diffraction (PXRD) approach. On a fundamental level, COF-505 is constructed from organic helices that are covalently linked within the thread, while neighboring helices are held woven with copper(I) ions serving as the points of registry. Upon removal of these copper(I) templates, the threads are endowed with large degrees of freedom to move about the crossing points, which results in a ten-fold increase of elasticity, as observed by nanoindentation using atomic force microscopy (AFM). Owing to the entanglement of the threads, the underlying topology of the structure remains intact upon demetalation. Copper(I) ions can be added back to the demetalated material to recover the structure of the as-synthesized COF; the demelation and remetalation process can be performed in a reversible manner.

In Chapter III, the design principle of woven COFs expanded to structures with large guest accessible internal void space within the structure. It was speculated that this parameter determines the magnitude of the thread movement upon demetalation. The original COF-505 was found to have a two-fold interpenetrated and consequently dense structure. Since it was believed that this might restrict the dynamics of the threads, two strategies were devised to prevent the formation of interpenetration in derivative woven structures: (i) A shorter ditopic linker, p-phenylenediamine (PDA), was employed instead of BZ to yield COF-504. The decreased pore size of the structure has limited internal space thus preventing framework interpenetration. (ii) Alternatively a non-interpenetrated framework can be formed using BZ as the linker when a bulky anion (diphenylphosphinate) was employed during COF synthesis. Post-synthetic anion exchange with smaller BF4- counterions yielded COF-506, a non-interpenetrated analogue of COF-505. The porosity of the two frameworks was investigated by vapor and dye adsorption, which confirmed the guest accessibility of their interior. In COF-506, the member of the series with the largest guest accessible void space, demetalation was found to affect structural dynamics within the structure. Spatial dislocations of the threads within the demetalated COF-506 structure allow for uptake of dye molecules that exceed the pore size of its metalated counterpart.

As the crystallinity of COFs heavily relies on the full reversibility of bond formation during the solvothermal synthesis, COF formation conditions can be highly specific for one type of linkage, or even one particular framework. The development of solid-state anthracene photodimerization as a new linkage for COF synthesis is detailed in Chapter IV. The key feature of this strategy is to pre-organize photoreactive anthracene monomers in a face-to-face manner in the solid state. This arrangement allows for exclusively lateral [4 + 4] cycloaddition reactions in the solid state upon UV exposure to target single-crystal-to-single-crystal transformation through C-C bond formation. To employ this approach to the synthesis of woven COFs the copper(I)-bisphenanthroline core was functionalized with anthracene moieties that serve as points of extension. Various packing modes resulted from different crystallization conditions, however only the undesirable face-to-edge anthracene stacking was observed. Fluorine atoms were subsequently installed on the 1, 2, 3, and 4 positions of the anthracene units which effectively enhanced the cofacial interaction of neighboring anthracenes, but no reactivity towards dimerization was observed upon UV treatment. Further studies of the molecular analogue, 1,2,3,4-tetralfuoro-9-phenylanthracene, revealed that the dimerization was only observed in solution, but not in the solid state, which could be attributed to the large energy cost of phenyl rotation and movement upon formation of the C9-C10 bond. Future work should thus focus on the functionalization of the 2 position of anthracene which is remote from the reaction site for dimerization.

Chapter V focuses on the discovery of higher modes of entanglement beyond woven structures. By reacting the tetrahedral aldehyde-functionalized copper(I) bisphenanthroline complex with square planar 4',4''',4''''',4'''''''-(ethene-1,1,2,2-tetrayl)tetrakis(([1,1'-biphenyl]-4-amine)) linkers (TBPA), the first interlocking COF-500 was synthesized. COF-500 is comprised of entangled 1D corner-sharing ladders and crystallized in a pts topology. Interlocking structures are fundamentally different from woven structures as their entanglement is based on closed rings which ensures that the entities remain entangled. Upon demetalation, the structure became less open, indicated by the decreased nitrogen sorption capacity. Elucidation of structural change accompanying this process is provided by solid-state photoluminescence measurement. Fluorescence of the material was turned on after demelataion and this can be attributed to restricted rotation of the phenyl rings of TBPA when the interlocked ladders move towards each other within the rigid ring systems. THF vapor adsorption studies highlight the dynamic behavior of these interlocked ladders as the demetalated material has a similar THF uptake with COF-500, in a manner that is analogues to swelling of polymers. A significant decrease of fluorescence response further confirms opening-up of demetalated structure in the presence of THF.

Finally, in Chapter VI, a library of woven topologies were identified. By translating the geometries into linear line segments (sticks) joined at corners in their optimal embeddings, 2D and 3D woven and polycatenated structures can be viewed as an extended family of molecular knots and links. Based on mathematical calculations, the most plausible topologies that can be woven were systematically enumerated. Ripe synthetic targets of 2D and 3D weavings and polycatenanes were also provided.

Structure of Guests in MOF and Their Applications

by

Ievgen Kapustin

Doctor of Philosophy in Chemistry

University of California, Berkeley

Professor Omar M. Yaghi, Chair

Chapter 1. Introduction to the fundamentals of reticular chemistry, metal-organic frameworks (MOFs), crystallographic studies of MOFs, and sorption studies of MOFs.

Chapter 2. MOF-520 is used to coordinatively bind and align molecules of varying size, complexity, and functionality. The reduced motional degrees of freedom obtained with this coordinative alignment method allow the structures of molecules to be determined by single-crystal x-ray diffraction techniques. The chirality of the MOF backbone also serves as a reference in the structure solution for an unambiguous assignment of the absolute configuration of bound molecules. Sixteen molecules representing four common functional groups (primary alcohol, phenol, vicinal diol, and carboxylic acid), ranging in complexity from methanol to plant hormones (gibberellins, containing eight stereocenters), are crystallized and have their precise structure determined. Single and double bonds in gibberellins can be distinguished crystallographically. A racemic mixture of jasmonic acid is crystallized enantioselectively and its absolute configuration is determined for the first time.

Chapter 3. Despite numerous studies on chemical and thermal stability of MOF, mechanical stability remains largely undeveloped. To date, no strategy exists to control the mechanical deformation of MOFs under ultrahigh pressure. Here, we show that the mechanically unstable MOF-520 can be retrofitted by precise placement of a rigid 4,4′-biphenyldicarboxylate (BPDC) linker as a “girder” to afford a mechanically robust framework: MOF-520-BPDC. This retrofitting alters how the structure deforms under ultrahigh pressure and thus leads to a drastic enhancement of its mechanical robustness. While in the parent MOF-520 the pressure transmitting medium molecules diffuse into the pore and expand the structure from the inside upon compression, the girder in the new retrofitted MOF-520-BPDC prevents the framework from expansion by linking two adjacent secondary building units together. As a result, the modified MOF is stable under hydrostatic compression in a diamond-anvil cell up to 5.5 gigapascal. The increased mechanical stability of MOF-520-BPDC prohibits the typical amorphization observed for MOFs in this pressure range. Direct correlation between the orientation of these girders within the framework and its linear strain was estimated, providing new insights for the design of MOFs with optimized mechanical properties.

Chapter 4. Atmospheric water is a resource equivalent to ~10% of all fresh water in lakes on Earth. However, an efficient process for capturing and delivering water from air, especially at low humidity levels (down to 20%), has not been developed. We report the design and demonstration of a device based on a porous metal-organic framework {MOF-801, [Zr6O4(OH)4(fumarate)6]} that captures water from the atmosphere at ambient conditions by using low-grade heat from natural sunlight at a flux of less than 1 sun (1 kilowatt per square meter). This device is capable of harvesting 2.8 liters of water per kilogram of MOF daily at relative humidity levels as low as 20% and requires no additional input of energy.

Chapter 5. Water scarcity is a particularly severe challenge in arid and desert climates. While a substantial amount of water is present in the form of vapor in the atmosphere, harvesting this water by state-of-the-art dewing technology can be extremely energy intensive and impractical, particularly when the relative humidity (RH) is low (i.e., below ~40% RH). In contrast, atmospheric water generators that utilize sorbents enable capture of vapor at low RH conditions and can be driven by the abundant source of solar-thermal energy with higher efficiency. Here, we demonstrate an air-cooled sorbent-based atmospheric water harvesting device using the metal−organic framework (MOF)-801 operating in an exceptionally arid climate (10–40% RH) and sub-zero dew points (Tempe, Arizona, United States) with a thermal efficiency (solar input to water conversion) of ~14%. We predict that this device delivered over 0.25 L of water per kg of MOF for a single daily cycle.

Chapter 6. Energy-efficient production of water from desert air has not been developed. A proof-of-concept device for harvesting water at low relative humidity was reported; however, it only delivers droplets of water but not of sufficient quantity to be collected. Here, we report a laboratory-to-desert experiment where a prototype employing up to 1.2 kg of metal-organic framework-801 was tested in the laboratory and later in the desert of Arizona, United States. It produced 100 grams of water per kilogram of MOF-801 per day-and-night cycle, using only natural cooling and ambient sunlight as a source of energy. We also report an aluminum-based MOF-303, which delivers more than twice the amount of water. The desert experiment uncovered key parameters pertaining to the energy, material, and air requirements for efficient production of water from desert air, even at a sub-zero dew point.