The fate of our times is characterized by rationalization and intellectualization and, above all, by the disenchantment of the world. —Max Weber (Science as vocation)
Design and Synthesis of Hierarchically Mesoporous Zr-MOFs for Enhanced Catalytic Activity & Adsorption Capacity
A hierarchically mesoporous (HM) UiO-66-F4 shell with ∼8 nm mesopores can be iteratively grown on top of UiO-66 nanoparticle (NP) seeds over several cycles templated by Pluronic F-127 micelles. Presumably, the Pluronic micelles that were formed in water can surround UiO-66 NPs to facilitate the overgrowth of an HM-UiO-66-F4 shell in the presence of ZrIV precursors and BDC-F4 linkers. The UiO-66 NP seeds play an important role in directing the continuous growth of the HM-UiO-66-F4 shell, as only a nonporous phase was obtained in their absence. This template-assisted, seed-mediated method can be extended to produce other UiO-66-X (X = (OH)2, (COOH)2, etc.) shells, demonstrating its generality for the UiO-66 family of metal-organic frameworks. Notably, the incorporation of mesopores into the thrice-overgrown UiO-66@HM|3rd-UiO-66-F4 materials leads to impressive enhancements in the per-mass uptake capacity of Direct Blue 86, a large anionic dye: 320% better than the parent UiO-66 seeds and 150% better than that for a [UiO-66 + UiO-66-F4] physical mixture at the same mass proportion. Similar enhancements were also observed in the catalyzed oxidation of thioanisole.
Using a Multi‐Shelled Hollow Metal-Organic Framework as a Host to Switch the Guest‐to‐Host and Guest‐to‐Guest Interactions
A bio-inspired design of using metal-organic framework (MOF) microcrystals with well‐defined multi‐shelled hollow structures was used as a matrix to host multiple guests including molecules and nanoparticles at separated locations to form a hierarchical material, mimicking biological structures. The interactions such as energy transfer (ET) between different guests are regulated by precisely fixing them in the MOF shells or encapsulating them in the cavities between the MOF shells. The proof‐of‐concept design is demonstrated by hosting chromophore molecules including rhodamine 6G (R6G) and 7‐amino‐4‐(trifluoromethyl)coumarin (C‐151), as well as metal nanoparticles (Pd NPs) into the multi‐shelled hollow zeolitic imidazolate framework‐8 (ZIF‐8). We could selectively establish or diminish the guest‐to‐framework and guest‐to‐guest ET. This work provides a platform to construct complex multifunctional materials, especially those need precise separation control of multi‐components. [This work was accomplished in Tsung Group @ Boston College (Chemistry Department).]
A Stretchable Electronic Fabric Artificial Skin with Pressure‐, Lateral Strain‐, and Flexion‐Sensitive Properties
A stretchable and multiple‐force‐sensitive electronic fabric based on stretchable coaxial sensor electrodes is fabricated for artificial‐skin application. This electronic fabric has only one kind of sensor unit, which is composed of polyimide fiber, silver nanowires, and a PDMS/carbon black polymer layer. By weaving the sensor units into one network, the fabric can simultaneously map and quantify the mechanical stresses induced by normal pressure, lateral strain, and flexion. [This work was accomplished in Yulab @ USTC.]
Creating a Direct Interface between Nanoparticle Catalysts and Metal-Organic Frameworks via in situ Replacement of Capping Agent (Submitted)
In this work, a well-defined, clean interface between metal nanoparticles (NPs) and metal-organic frameworks (MOFs) is achieved in NP@MOF type core-shell materials by utilizing the dynamic nature of weakly adsorbed capping agents on metal NPs. Using this design, metal NP@ZIF-8 and metal NP@UiO-66-F4 with a clean interface have been synthesized. A mechanism that the capping agents gradually dissociate from the metal surface and are replaced in situ by MOFs during the formation of the MOF shell is demonstrated. Benefited from the direct contact of metal NPs and MOFs without capping agents in between, the materials outperform the ones with ill-defined interfaces in the hydrogenation of an α,β-unsaturated aldehyde, displaying a higher selectivity for the formation of unsaturated alcohols. This study sheds light on improving the heterogeneous catalysis performance by well engineering the interface on the catalysts.
[This work was accomplished in Tsung Group @ Boston College (Chemistry Department).]
Engineering missing linkers into UiO-66 post-synthesis and during linker exchange: controlling number of defects through a [modulator + linker] treatment (Submitted)
Post-synthesis treatment of UiO-66 materials with a combination of benzoic acid modulator and terephthalic acid (BDC) linker can readily tune the levels of missing-linker defects in these MOFs with no change in sample morphology and minimal mass loss. For a near-ideal UiO-66 sample, this strategy can increase the number of missing linker/node (ML/N) from 0.6 to 2.2, resulting in ~5-fold enhancement in catalytic activities for a sulfide oxidation reaction. In ligand-exchange experiments with BDC-X (X = NH2, (OH)2, (COOH)2, and F4), this treatment can modulate the ML/N ratio in the 1.2-4.2 range, in stark contrast to the loss of defects normally observed in conventional post-synthesis exchange experiments.
—Welcome to join my current and previous groups if you are researchers devoted to chemistry and/or materials science! They are: Nguyen lab at Northwestern University, Tsung group at Boston College, and Yulab at USTC.—