Engineering Functional Porous Materials for Gas Adsorption and Heterogeneous Catalysis

In the past two decades, functional porous materials have gained tremendous attention in scientific and technological research. Metal-organic frameworks (MOFs) and porous polymer networks (PPNs) emerged as novel categories of porous materials with ultrahigh porosity, enormous surface area, tunable pore size and shape, and adjustable functionalization. Hence, MOFs/PPNs have demonstrated great potential for gas adsorption and heterogeneous catalysis, which has been my research focus. Firstly, utilizing labile MOFs as templates, a general post-synthetic method was invented to synthesize a series of Ti-MOFs. The crystallinity of these Ti-MOFs was well maintained throughout, as confirmed from powder X-ray diffractions and gas adsorption measurements. This work provides a first time reported systematic strategy to construct Ti-MOFs while highlighting the potential of Ti-MOFs in photocatalytic applications. Two stable porphyrin based PPNs have been synthesized through a facile one-pot approach by the aromatic substitution reactions of pyrrole and aldehydes. Among them, PPN-24(Fe) performs high catalytic efficiency as a biomimetic catalyst for the oxidation reaction of 2, 2’-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) in the presence of H2O2. In next section, we report the design of a flexible Zr-MOF system, namely PCN-700 series, for the realization of switchable catalysis in cycloaddition reactions of CO2 with epoxides. The breathing amplitudes of the PCN-700 series are magnified through pre-functionalization of organic linkers and post-synthetic linker installation. Experiments and molecular simulations confirm that the catalytic activities of the PCN-700 series can be switched on and off upon guest-induced reversible structural transformation. MOFs have become a burgeoning field of research and a great potential candidate for hydrogen storage. As way of example, MOFs constructed by carboxylate, azolate or mixed linkers, are discussed in the context of hydrogen storage. Last but not least, the post-synthetic modifications on MOF materials to increase the hydrogen storage capacities will be carefully illustrated. Intensive efforts have been made to investigate PPNs as one type of the most promising candidates for carbon capture. A detailed correlation study between the structural and chemical features of PPNs and their adsorption capacities will be discussed, mainly focusing on the physical interactions and chemical reactions

Construction of hierarchically porous metal–organic frameworks through linker labilization

AbstractA major goal of metal–organic framework (MOF) research is the expansion of pore size and volume. Although many approaches have been attempted to increase the pore size of MOF materials, it is still a challenge to construct MOFs with precisely customized pore apertures for specific applications. Herein, we present a new method, namely linker labilization, to increase the MOF porosity and pore size, giving rise to hierarchical-pore architectures. Microporous MOFs with robust metal nodes and pro-labile linkers were initially synthesized. The mesopores were subsequently created as crystal defects through the splitting of a pro-labile-linker and the removal of the linker fragments by acid treatment. We demonstrate that linker labilization method can create controllable hierarchical porous structures in stable MOFs, which facilitates the diffusion and adsorption process of guest molecules to improve the performances of MOFs in adsorption and catalysis.</jats:p

Chromium metal organic frameworks and synthesis of metal organic frameworks

The present invention relates to monocrystalline metal organic frameworks comprising chromium ions and carboxylate ligands and the use of the same, for example their use for storing a gas. The invention also relates to methods for preparing metal organic frameworks comprising chromium, titanium or iron ions and carboxylate ligands. The methods of the invention allow such metal organic frameworks to be prepared in monocrystalline or polycrystalline forms.U

Chromium metal organic frameworks and synthesis of metal organic frameworks

The present invention relates to monocrystalline metal organic frameworks comprising chromium ions and carboxylate ligands and the use of the same, for example their use for storing a gas. The invention also relates to methods for preparing metal organic frameworks comprising chromium, titanium or iron ions and carboxylate ligands. The methods of the invention allow such metal organic frameworks to be prepared in monocrystalline or polycrystalline forms.U

Chromium metal organic frameworks and synthesis of metal organic frameworks

The present invention relates to monocrystalline metal organic frameworks comprising chromium ions and carboxylate ligands and the use of the same, for example their use for storing a gas. The invention also relates to methods for preparing metal organic frameworks comprising chromium, titanium or iron ions and carboxylate ligands. The methods of the invention allow such metal organic frameworks to be prepared in monocrystalline or polycrystalline forms.U

A versatile synthetic route for the preparation of titanium metal-organic frameworks

Through a versatile synthetic strategy, High Valence Metathesis and Oxidation (HVMO), a series of Ti-MOFs with predesigned topologies and structures were synthesized.</p

Flexible Zirconium Metal‐Organic Frameworks as Bioinspired Switchable Catalysts

Flexible metal–organic frameworks (MOFs) are highly desirable in host–guest chemistry owing to their almost unlimited structural/functional diversities and stimuli‐responsive pore architectures. Herein, we designed a flexible Zr‐MOF system, namely PCN‐700 series, for the realization of switchable catalysis in cycloaddition reactions of CO2 with epoxides. Their breathing behaviors were studied by successive single‐crystal X‐ray diffraction analyses. The breathing amplitudes of the PCN‐700 series were modulated through pre‐functionalization of organic linkers and post‐synthetic linker installation. Experiments and molecular simulations confirm that the catalytic activities of the PCN‐700 series can be switched on and off upon reversible structural transformation, which is reminiscent of sophisticated biological systems such as allosteric enzymes. An open and shut case: The inherent cavities and dynamic behavior of flexible MOFs, bear a close resemblance to regulatory enzymes. Switchable activation and deactivation of their catalytic properties occurs on pore opening and closing by solvation/solvent removal

Thermodynamically Guided Synthesis of Mixed-Linker Zr-MOFs with Enhanced Tunability

Guided by thermodynamics, we have synthesized two mixed-linker zirconium-based metal–organic frameworks (Zr-MOFs), namely, PCN-133 and PCN-134. Both of them possess a layer-pillar structure, in which the connection between Zr₆ clusters and primary BTB linkers form a (3,6)-connected <b>kdg</b> layer that is further extended into 3D frameworks by auxiliary DCDPS/TCPP linkers (BTB = benzene tribenzoate, DCDPS = 4,4′-dicarboxydiphenyl sulfone, TCPP = tetrakis­(4-carboxyphenyl)­porphyrin). PCN-134 demonstrates high porosity (N₂ uptake of 717 cm³·g^–1 and BET surface area of 1946 cm²·g^–1) and excellent chemical stability in aqueous solutions with pH values ranging from 0 to 13. More importantly, PCN-134 tolerates the partial absence of auxiliary linkers leading to structural defects during the assembly process while preserving its framework integrity. Furthermore, the defect density can be systematically controlled by tuning the occupancy of the auxiliary linker, which in turn affects the MOF properties. For instance, the dichromate uptake of PCN-134 is tuned by adjusting the BTB/TCPP ratios, which gives rise to an efficient dichromate absorbent when the TCPP molar ratio in linkers is set as 22%. In addition, the photocatalytic reduction of Cr­(VI) in aqueous solution was also performed by PCN-134–22%TCPP which exhibits excellent catalytic activity. This work not only opens up a new synthetic route toward mixed-linker MOFs, but also provides tunable control of MOF defects and, in turn, the properties

Thermodynamically Guided Synthesis of Mixed-Linker Zr-MOFs with Enhanced Tunability

Guided by thermodynamics, we have synthesized two mixed-linker zirconium-based metal–organic frameworks (Zr-MOFs), namely, PCN-133 and PCN-134. Both of them possess a layer-pillar structure, in which the connection between Zr₆ clusters and primary BTB linkers form a (3,6)-connected <b>kdg</b> layer that is further extended into 3D frameworks by auxiliary DCDPS/TCPP linkers (BTB = benzene tribenzoate, DCDPS = 4,4′-dicarboxydiphenyl sulfone, TCPP = tetrakis­(4-carboxyphenyl)­porphyrin). PCN-134 demonstrates high porosity (N₂ uptake of 717 cm³·g^–1 and BET surface area of 1946 cm²·g^–1) and excellent chemical stability in aqueous solutions with pH values ranging from 0 to 13. More importantly, PCN-134 tolerates the partial absence of auxiliary linkers leading to structural defects during the assembly process while preserving its framework integrity. Furthermore, the defect density can be systematically controlled by tuning the occupancy of the auxiliary linker, which in turn affects the MOF properties. For instance, the dichromate uptake of PCN-134 is tuned by adjusting the BTB/TCPP ratios, which gives rise to an efficient dichromate absorbent when the TCPP molar ratio in linkers is set as 22%. In addition, the photocatalytic reduction of Cr­(VI) in aqueous solution was also performed by PCN-134–22%TCPP which exhibits excellent catalytic activity. This work not only opens up a new synthetic route toward mixed-linker MOFs, but also provides tunable control of MOF defects and, in turn, the properties