A packaged toolbox with stabilization and functionalization strategies for robust and multifunctional metal–organic framework (MOF) materials has been summarized and discussed.

Sufficient pore size, appropriate stability, and hierarchical porosity are three prerequisites for open frameworks designed for drug delivery, enzyme immobilization, and catalysis involving large molecules. Herein, we report a powerful and general strategy, linker thermolysis, to construct ultrastable hierarchically porous metal-organic frameworks (HP-MOFs) with tunable pore size distribution. Linker instability, usually an undesirable trait of MOFs, was exploited to create mesopores by generating crystal defects throughout a microporous MOF crystal via thermolysis. The crystallinity and stability of HP-MOFs remain after thermolabile linkers are selectively removed from multivariate metal-organic frameworks (MTV-MOFs) through a decarboxylation process. A domain-based linker spatial distribution was found to be critical for creating hierarchical pores inside MTV-MOFs. Furthermore, linker thermolysis promotes the formation of ultrasmall metal oxide nanoparticles immobilized in an open framework that exhibits high catalytic activity for Lewis acid-catalyzed reactions. Most importantly, this work provides fresh insights into the connection between linker apportionment and vacancy distribution, which may shed light on probing the disordered linker apportionment in multivariate systems, a long-standing challenge in the study of MTV-MOFs.

Metal–organic frameworks (MOFs), constructed from organic linkers and inorganic building blocks, are well-known for their high crystallinity, high surface areas, and high component tunability. The stability of MOFs is a key prerequisite for their potential practical applications in areas including storage, separation, catalysis, and biomedicine since it is essential to guarantee the framework integrity during utilization. However, MOFs are prone to destruction under external stimuli, considerably hampering their commercialization. In this Review, we provide an overview of the situations where MOFs undergo destruction due to external stimuli such as chemical, thermal, photolytic, radiolytic, electronic, and mechanical factors and offer guidelines to avoid unwanted degradation happened to the framework. Furthermore, we discuss possible destruction mechanisms and their varying derived products. In particular, we highlight cases that utilize MOF instability to fabricate varying materials including hierarchically porous MOFs, monolayer MOF nanosheets, amorphous MOF liquids and glasses, polymers, metal nanoparticles, metal carbide nanoparticles, and carbon materials. Finally, we provide a perspective on the utilization of MOF destruction to develop advanced materials with a superior hierarchy for various applications.

Adsorptive separation of acetylene (C2H2) from carbon dioxide (CO2) promises a practical way to produce high-purity C2H2 required for industrial applications. However, challenges exist in the pore environment engineering of porous materials to recognize two molecules due to their similar molecular sizes and physical properties. Herein, we report a strategy to optimize pore environments of multivariate metal–organic frameworks (MOFs) for efficient C2H2/CO2 separation by tuning metal components, functionalized linkers, and terminal ligands. The optimized material UPC-200­(Al)-F-BIM, constructed from Al3+ clusters, fluorine-functionalized organic linkers, and benzimidazole terminal ligands, demonstrated the highest separation efficiency (C2H2/CO2 uptake ratio of 2.6) and highest C2H2 productivity among UPC-200 systems. Experimental and computational studies revealed the contribution of small pore size and polar functional groups on the C2H2/CO2 selectivity and indicated the practical C2H2/CO2 separation of UPC-200­(Al)-F-BIM.

Targeted fluorescent molecular imaging probes may provide an optimal means of detecting disease. Stable, organic fluorophores can be repeatedly excited in vivo by propagated light and consequentially can provide large signal-to-noise ratios (SNRs) for image detection of target tissues. In the literature, many small animal imaging studies are performed with a red excitable dye, Cy5.5, conjugated to the targeting component. We report the comparison of the in vivo fluorescent imaging performance of a near-IR (NIR) and a red-excitable dye. Epidermal growth factor (EGF) was conjugated with Cy5.5 [excitation/emission (ex/em), 660710 nm] or IRDye 800CW (ex/em: 785830 nm) for imaging EGF receptor (EGFr) positive (MDA-MB-468) and/or negative (MDA-MB-435) human breast cancer cell lines in subcutaneous xenograft models. The conjugates were injected intravenously at 1-nmol-dye equivalent with and without anti-EGFr monoclonal antibody C225, preadministered 24 h prior as a competitive ligand to EGFr. Our images show that while both agents target EGFr, the EGF-IRDye 800CW evidenced a significantly reduced background and enhanced the tumor-to-background ratio (TBR) compared to the EGF-Cy5.5. Immunohistochemistry shows that EGF causes activation of the EGFr signaling pathway, suggesting that prior to use as a targeting, diagnostic agent, potential deleterious effects should be considered.