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1. Surprisingly big linker-dependence of activity and selectivity in CO ₂ reduction by an iridium( i ) pincer complex

   https://doi.org/10.1039/D0CC03207G  

   Hu, Gongfang; Jiang, Jianbing “Jimmy”; Kelly, H. Ray; Matula, Adam J.; Wu, Yueshen; Romano, Neyen; Mercado, Brandon Q.; Wang, Hailiang; Batista, Victor S.; Crabtree, Robert H.; et al (August 2020, Chemical Communications)

   null (Ed.)

   Here, we report the quantitative electroreduction of CO 2 to CO by a PNP-pincer iridium( i ) complex bearing amino linkers in DMF/water. The electrocatalytic properties greatly depend on the choice of linker within the ligand. The complex 3-N is far superior to the analogues with methylene and oxygen linkers, showing higher activity and better selectivity for CO 2 over proton reduction. 

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2. Simulation of interlayer coupling for electroactive covalent organic framework design

   https://doi.org/10.1063/5.0206246  

   Leo, Tanner M; Robbins, Megan; Sullivan, Alana; Thornes, Henry; Fitzsimmons, Garrett; Goodey, Alyssa; Kowalczyk, Tim (May 2024, The Journal of Chemical Physics)

   Porous, stacked two-dimensional covalent organic frameworks (2D COFs) bearing semiconducting linkers can support directional charge transfer across adjacent layers of the COF. To better inform the current and possible future design rules for enhancing electron and hole transport in such materials, an understanding of how linker selection and functionalization affects interlayer electronic couplings is essential. We report electronic structure simulation and analysis of electronic couplings across adjacent linker units and to encapsulated species in functionalized electroactive 2D COFs. The detailed dependence of these electronic couplings on interlayer interactions is examined through scans along key interlayer degrees of freedom and through configurational sampling from equilibrium molecular dynamics on semiempirical potential energy surfaces. Beyond affirming the sensitivity of the electronic coupling to interlayer distance and orientation, these studies offer guidance toward linker functionalization strategies for enhancing charge carrier transport in electroactive 2D COFs. 

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3. Ionothermal Synthesis of Metal‐Organic Frameworks Using Low‐Melting Metal Salt Precursors**

   https://doi.org/10.1002/anie.202218252  

   Azbell, Tyler J.; Pitt, Tristan A.; Bollmeyer, Melissa M.; Cong, Christina; Lancaster, Kyle M.; Milner, Phillip J. (March 2023, Angewandte Chemie International Edition)

   Abstract Metal‐organic frameworks (MOFs) are porous, crystalline materials constructed from organic linkers and inorganic nodes with myriad potential applications in chemical separations, catalysis, and drug delivery. A major barrier to the application of MOFs is their poor scalability, as most frameworks are prepared under highly dilute solvothermal conditions using toxic organic solvents. Herein, we demonstrate that combining a range of linkers with low‐melting metal halide (hydrate) salts leads directly to high‐quality MOFs without added solvent. Frameworks prepared under these ionothermal conditions possess porosities comparable to those prepared under traditional solvothermal conditions. In addition, we report the ionothermal syntheses of two frameworks that cannot be prepared directly under solvothermal conditions. Overall, the user‐friendly method reported herein should be broadly applicable to the discovery and synthesis of stable metal‐organic materials. 

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4. Tuning Material Properties of Porous Organic Cage CC3 with Postsynthetic Dynamic Covalent Chemistry

   https://doi.org/10.1002/ejoc.202101507  

   Rivera, Matthew_P; Liu, Ming; He, Donglin; Lively, Ryan_P (January 2022, European Journal of Organic Chemistry)

   Abstract Porous organic cages (POCs) represent a new class of microporous materials with an impressive breadth of potential applications. One of their many advantages is the degree of tunability of cage properties, similar to that seen in more established microporous materials like metal‐organic frameworks. In this work, a prototypical POC, CC3, is used to explore the potential to tune cage properties via post‐synthetic dynamic covalent chemistry. Ethylenediamine, the linker used in another POC, CC1, was partially substituted into the CC3 cage structure to varying degrees based on the starting relative molar ratios. The resulting products were investigated for the relative distribution of the two linkers, crystallinity, and surface area. It was found that even when small amounts of other compatible diamine linkers are introduced, they substitute into the existing cages, although some structural products are apparently favored over others within the reactant ratios investigated. 

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5. Inter‐Network Charge‐Transfer Excited State Formation Within a Two‐fold Catenated Metal–Organic Framework

   https://doi.org/10.1002/chem.202202978  

   Nath, Akashdeep; Chawla, Sakshi; K_De, Arijit; Deria, Pravas; Mandal, Sukhendu (November 2022, Chemistry – A European Journal)

   Abstract Charge‐transfer excited state (CTES) defines the ability to split photon energy into work producing redox equivalents suitable for photocatalysis. Here, we report inter‐net CTES formation within a two‐fold catenated crystalline metal–organic framework (MOF), constructed with two linkers, N,N′‐di(4‐pyridyl)‐1,4,5,8‐naphthalenetetracarboxydiimide (DPNDI) and 2,6‐dicarboxynaphthalene (NDC). The structural flexibility puts two complementary linkers from two nets in a proximal position to interact strongly. Supported by the electrochemical and steady‐state electronic spectroscopic data, this ground‐state interaction facilitates forming CTES that can be populated by direct excitation. We map the dynamics of the CTES which persists over a few nanoseconds and highlight the utilities of such relatively long‐lived CTES as enhanced conductivity of the MOF under light over that measured in dark and as a proof‐of‐the‐principle test, photo‐reduction of methyl viologen under white light. 

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