Structure-Assisted Functional Anchor Implantation in Robust Metal–Organic Frameworks with Ultralarge Pores

A facile functionalization assisted by the structural attributes of PCN-333 has been studied while maintaining the integrity of the parent MOF including ultralarge pores, chemical robustness, and crystallinity. Herein we thoroughly analyzed ligand exchange phenomena in PCN-333 and demonstrate that the extent of exchange can be tailored by varying the exchange conditions as potential applications may require. Through this method a variety of functional groups are incorporated into PCN-333. To further show the capabilities of this system introduction of a BODIPY fluorophore as a secondary functionality was performed to the functionalized framework via a click reaction. We anticipate the PCN-333 with functional anchor can serve as a stable platform for further chemistry to be explored in future applications

Dual Exchange in PCN-333: A Facile Strategy to Chemically Robust Mesoporous Chromium Metal–Organic Framework with Functional Groups

A facile preparation of a mesoporous Cr-MOF, PCN-333­(Cr) with functional group, has been demonstrated through a dual exchange strategy, involving a sequential ligand exchange and metal metathesis process. After optimization of the exchange system, the functionalized PCN-333­(Cr), N₃–PCN-333­(Cr) shows well maintained crystallinity, porosity, as well as much improved chemical stability. Because of the exceptionally large pores (∼5.5 nm) in PCN-333­(Cr), a secondary functional moiety, Zn-TEPP with a size of 18 Å × 18 Å, has been successfully clicked into the framework. In this article, we have also analyzed kinetics and thermodynamics during dual exchange process, showing our attempts to interpret the exchange event in the PCN-333. Our findings not only provide a highly stable mesoporous Cr-MOF platform for expanding MOF-based applications, but also suggest a route to functionalized Cr-MOF which may have not been achievable through conventional approaches

3D Long-Range Triplet Migration in a Water-Stable Metal–Organic Framework for Upconversion-Based Ultralow-Power <i>in Vivo</i> Imaging

Triplet–triplet annihilation upconversion (TTA-UC) has gained increasing attention because it allows for harvesting of low-energy photons in the solar spectrum with high efficiency in relevant applications including solar cells and bioimaging. However, the utilization of conventional TTA-UC systems for low-power bioapplications is significantly hampered by their general incompatibility and low efficiency in aqueous media. Herein we report a metal–organic framework (MOF) as a biocompatible nanoplatform for TTA-UC to realize low-power <i>in vivo</i> imaging. Our MOF consists of a porphyrinic sensitizer in an anthracene-based Zr-MOF as a TTA-UC platform. In particular, closely aligned chromophores in the MOF facilitate a long-range 3D triplet diffusion of 1.6 μm allowing efficient energy migration in water. The tunable ratio between sensitizer and annihilator by our synthetic method also allows an optimization of the system for maximized TTA-UC efficiency in water at a very low excitation power density. Consequently, the low-power imaging of lymph node in a live mouse was successfully demonstrated with an excellent signal-to-noise ratio (SNR > 30 at 5 mW cm^–2)

Flexible Zirconium MOF as the Crystalline Sponge for Coordinative Alignment of Dicarboxylates

Because of their permanent porosity and unparalleled structural diversities, flexible metal–organic frameworks (MOFs) are promising and highly desirable in host–guest chemistry. In this work, we employed a flexible Zr-MOF system, namely PCN-700 species, as the crystalline sponge for guest inclusion. A family of linear dicarboxylate ligands was adsorbed in the void space of PCN-700, which were subsequently confirmed by crystallographic observation. The stretching degree of the PCN-700 series was varied by means of dicarboxylate encapsulation through coordinative alignment

A Route to Metal–Organic Frameworks through Framework Templating

A microporous metal–organic framework (MOF), PCN-922 [Cu₄(ETTB)], containing a dendritic octatopic organic linker and a Cu₂-paddlewheel structural motif, has been synthesized by using a Zn₂-paddlewheel-based MOF as a template to prearrange the linkers for the Cu₂-based MOF target. PCN-922 shows permanent porosity and excellent gas adsorption capacity

A Route to Metal–Organic Frameworks through Framework Templating

A microporous metal–organic framework (MOF), PCN-922 [Cu₄(ETTB)], containing a dendritic octatopic organic linker and a Cu₂-paddlewheel structural motif, has been synthesized by using a Zn₂-paddlewheel-based MOF as a template to prearrange the linkers for the Cu₂-based MOF target. PCN-922 shows permanent porosity and excellent gas adsorption capacity

A Route to Metal–Organic Frameworks through Framework Templating

A microporous metal–organic framework (MOF), PCN-922 [Cu₄(ETTB)], containing a dendritic octatopic organic linker and a Cu₂-paddlewheel structural motif, has been synthesized by using a Zn₂-paddlewheel-based MOF as a template to prearrange the linkers for the Cu₂-based MOF target. PCN-922 shows permanent porosity and excellent gas adsorption capacity

Flexible Zirconium MOF as the Crystalline Sponge for Coordinative Alignment of Dicarboxylates

Because of their permanent porosity and unparalleled structural diversities, flexible metal–organic frameworks (MOFs) are promising and highly desirable in host–guest chemistry. In this work, we employed a flexible Zr-MOF system, namely PCN-700 species, as the crystalline sponge for guest inclusion. A family of linear dicarboxylate ligands was adsorbed in the void space of PCN-700, which were subsequently confirmed by crystallographic observation. The stretching degree of the PCN-700 series was varied by means of dicarboxylate encapsulation through coordinative alignment

Cooperative Template-Directed Assembly of Mesoporous Metal–Organic Frameworks

Despite great efforts, the development of a reliable way to assemble mesoporous metal–organic frameworks (mesoMOFs) remains a challenge. In this work, we have designed a cooperative template system, comprising a surfactant (cetyltrimethylammonium bromide) and a chelating agent (citric acid), for the generation of a mesoMOF containing a hierarchical system of mesopores interconnected with microspores. The surfactant molecules form micelles and the chelating agent bridges the MOF and the micelles, making self-assembly and crystal growth proceed under the direction of the cooperative template. However, when the surfactant or the chelating agent was applied individually, no mesoMOF was obtained

Sequestering CO₂ for Short-Term Storage in MOFs: Copolymer Synthesis with Oxiranes

It is presently well-established that the synthesis of polycarbonates or cyclic carbonates from metal-catalyzed reactions of CO₂ and oxiranes provides a viable industrial process for the production of these important chemicals. In this study, we have demonstrated that CO₂ collected under aerobic conditions at atmospheric pressure over [Cu₃(btc)₂(H₂O)₃] (btc = benzene-1,3,5-tricarboxylate) or HKUST-1, a commercially available metal–organic framework material (MOF), can be utilized to synthesize poly­(propylene carbonate) from propylene oxide and CO₂ catalyzed by Co­(III) salen catalysts at optimal pressure. That is, CO₂ thermally released from the MOF material selectively affords copolymer in the pressure range that is not rate-limiting. Similar results were noted for the copolymerization of the much less reactive <i>cis</i>-2-butylene oxide monomer with CO₂. Comparative studies using CO₂ provided directly from a compressed gas source gave similar results. This investigation provides a baseline study for the practical use of atmospheric pressure or below CO₂ captured from point sources for the synthesis of useful chemicals without requiring mechanical compression