More Like this

1. Heterometallic multinuclear nodes directing MOF electronic behavior

   https://doi.org/10.1039/d0sc03053h  

   Ejegbavwo, Otega A.; Berseneva, Anna A.; Martin, Corey R.; Leith, Gabrielle A.; Pandey, Shubham; Brandt, Amy J.; Park, Kyoung Chul; Mathur, Abhijai; Farzandh, Sharfa; Klepov, Vladislav V.; et al (July 2020, Chemical Science)

   null (Ed.)

   Metal node engineering in combination with modularity, topological diversity, and porosity of metal–organic frameworks (MOFs) could advance energy and optoelectronic sectors. In this study, we focus on MOFs with multinuclear heterometallic nodes for establishing metal−property trends, i.e. , connecting atomic scale changes with macroscopic material properties by utilization of inductively coupled plasma mass spectrometry, conductivity measurements, X-ray photoelectron and diffuse reflectance spectroscopies, and density functional theory calculations. The results of Bader charge analysis and studies employing the Voronoi–Dirichlet partition of crystal structures are also presented. As an example of frameworks with different nodal arrangements, we have chosen MOFs with mononuclear, binuclear, and pentanuclear nodes, primarily consisting of first-row transition metals, that are incorporated in HHTP-, BTC-, and NIP-systems, respectively (HHTP 3− = triphenylene-2,3,6,7,10,11-hexaone; BTC 3− = 1,3,5-benzenetricarboxylate; and NIP 2− = 5-nitroisophthalate). Through probing framework electronic profiles, we demonstrate structure–property relationships, and also highlight the necessity for both comprehensive analysis of trends in metal properties, and novel avenues for preparation of heterometallic multinuclear isoreticular structures, which are critical components for on-demand tailoring of properties in heterometallic systems. 

   more » « less
2. Supramolecular photochemistry of encapsulated caged ortho -nitrobenzyl triggers

   https://doi.org/10.1039/c9pp00260j  

   Kamatham, Nareshbabu; Raj, A. Mohan; Givens, Richard S.; Da Silva, José P.; Ramamurthy, V. (October 2019, Photochemical & Photobiological Sciences)

   ortho -Nitrobenzyl ( o NB) triggers have been extensively used to release various molecules of interest. However, the toxicity and reactivity of the spent chromophore, o -nitrosobenzaldehyde, remains an unaddressed difficulty. In this study we have applied the well-established supramolecular photochemical concepts to retain the spent trigger o -nitrosobenzaldehyde within the organic capsule after release of water-soluble acids and alcohols. The sequestering power of organic capsules for spent chromophores during photorelease from ortho -nitrobenzyl esters, ethers and alcohols is demonstrated with several examples. 

   more » « less
3. Nested non-covalent interactions expand the functions of supramolecular polymer networks

   https://doi.org/10.1038/s41467-024-47666-x  

   Lundberg, David J.; Brown, Christopher M.; Bobylev, Eduard O.; Oldenhuis, Nathan J.; Alfaraj, Yasmeen S.; Zhao, Julia; Kevlishvili, Ilia; Kulik, Heather J.; Johnson, Jeremiah A. (December 2024, Nature Communications)

   Abstract Supramolecular polymer networks contain non-covalent cross-links that enable access to broadly tunable mechanical properties and stimuli-responsive behaviors; the incorporation of multiple unique non-covalent cross-links within such materials further expands their mechanical responses and functionality. To date, however, the design of such materials has been accomplished through discrete combinations of distinct interaction types in series, limiting materials design logic. Here we introduce the concept of leveraging “nested” supramolecular crosslinks, wherein two distinct types of non-covalent interactions exist in parallel, to control bulk material functions. To demonstrate this concept, we use polymer-linked Pd₂L₄metal–organic cage (polyMOC) gels that form hollow metal–organic cage junctions through metal–ligand coordination and can exhibit well-defined host-guest binding within their cavity. In these “nested” supramolecular network junctions, the thermodynamics of host-guest interactions within the junctions affect the metal–ligand interactions that form those junctions, ultimately translating to substantial guest-dependent changes in bulk material properties that could not be achieved in traditional supramolecular networks with multiple interactions in series. 

   more » « less
4. Structure, Dynamics, and Reactivity of Encapsulated Molecules in Restricted Spaces: Arylazoisoxazoles within an Octa Acid Capsule

   https://doi.org/10.1021/acs.langmuir.4c01996  

   Sunny, Amal Sam; Cleven, Elliott C; Kumar, Pravesh; Venkataramani, Sugumar; Walls, Jamie D; Ramamurthy, Vaidhyanathan (August 2024, Langmuir)

   In this study, a well-defined organic capsule assembled from two octa acid (OA) molecules acting as host and select arylazoisoxazoles (AAIO) acting as guests were employed to demonstrate that confined molecules have restricted freedom that translates into reaction selectivity in both ground and excited states. The behavior of these AAIO guests in confined capsules was found to be different from that found in both crystals, where there is very little freedom, and in isotropic solvents, where there is complete freedom. Through one-dimensional (1D) and two-dimensional (2D) 1H NMR spectroscopic experiments, we have established a relationship between structure, dynamics and reactivity of molecules confined in an OA capsule. Introduction of CF3 and CH3 substitution at the 4-position of the aryl group of AAIO reveals that in addition to space confinement, weak interactions between the guest and the OA capsule control the dynamics and reactivity of guest molecules. 1H NMR studies revealed that there is a temperature-dependence to guest molecules tumbling (180° rotation along the capsular short axis) within an OA capsule. While 1H NMR points to the occurrence of tumbling motion, MD simulations and simulation of the temperature-dependent NMR signals provide an insight into the mechanism of tumbling within OA capsules. Thermal and photochemical isomerization of AAIO were found to occur within an OA capsule just as in organic solvents. The observed selectivity noted during thermal and photo induced isomerization of OA encapsulated AAIOs can be qualitatively understood in terms of the well-known concepts due to Bell−Evans− Polanyi (BEP principle), Hammond and Zimmerman. 

   more » « less
5. Hydrogel microcapsules with photocatalytic nanoparticles for removal of organic pollutants

   https://doi.org/10.1039/c9en01108k  

   Liu, Jinrun; Chen, Hong; Shi, Xiaojie; Nawar, Saraf; Werner, Jörg G.; Huang, Gaoshan; Ye, Miaomiao; Weitz, David A.; Solovev, Alexander A.; Mei, Yongfeng (February 2020, Environmental Science: Nano)

   null (Ed.)

   Droplet-based microfluidics is used to fabricate thin shell hydrogel microcapsules for the removal of methylene blue (MB) from aqueous solutions. The microcapsules composed of a poly(methacrylic acid) hydrogel shell exhibit unique properties, including permeation, separation, purification, and reaction of molecular species. Photocatalytic TiO 2 and ZnO nanoparticles encapsulated in the microcapsules, i.e. photocatalyst in capsule (PIC), are used to remove organic pollutants using an adsorption–oxidation mechanism. A prototype flow microreactor is assembled to demonstrate a controllable water purification approach in short time using photocatalysts. Our studies of aqueous and homogeneous hydrogel environments for the photocatalysts provide important insights into understanding the effectiveness of MB removal. Hydrogel capsules have MB removal rate comparable to homogeneous particles. Further reduction of both capsule and photocatalyst sizes can potentially aid in quicker water purification. 

   more » « less