Integrating Photoactive Ligands into Crystalline Ultrathin 2D Metal-Organic Framework Nanosheets for Efficient Photoinduced Energy Transfer.

3D metal-organic frameworks (MOFs) have gained attention as heterogeneous photocatalysts due to their porosity and unique host-guest interactions. Despite their potential, MOFs face challenges, such as inefficient mass transport and limited light penetration in photoinduced energy transfer processes. Recent advancements in organic photocatalysis have uncovered a variety of photoactive cores, while their heterogenization remains an underexplored area with great potential to build MOFs. This gap is bridged by incorporating photoactive cores into 2D MOF nanosheets, a process that merges the realms of small-molecule photochemistry and MOF chemistry. This approach results in recyclable heterogeneous photocatalysts that exhibit an improved mass transfer efficiency. This research demonstrates a bottom-up synthetic method for embedding photoactive cores into 2D MOF nanosheets, successfully producing variants such as PCN-641-NS, PCN-643-NS, and PCN-644-NS. The synthetic conditions were systematically studied to optimize the crystallinity and morphology of these 2D MOF nanosheets. Enhanced host-guest interactions in these 2D structures were confirmed through various techniques, particularly solid-state NMR studies. Additionally, the efficiency of photoinduced energy transfer in these nanosheets was evidenced through photoborylation reactions and the generation of reactive oxygen species (ROS).

Elucidation of Substantial Differences in Ring-Opening Polymerization Outcomes from Subtle Variation of Glucose Carbonate-Based Monomer Substitution Patterns and Substituent Types.

The substituents present upon five-membered bicyclic glucose carbonate monomers were found to greatly affect the reactivities and regioselectivities during ring-opening polymerization (ROP), which contrast in significant and interesting ways from previous studies on similar systems, while also leading to predictable effects on the thermal properties of the resulting polycarbonates. Polymerization behaviors were probed for a series of five five-membered bicyclic 2,3-glucose-carbonate monomers having 4,6-ether, -carbonate, or -sulfonyl urethane protecting groups, under catalysis with three different organobase catalysts. Irrespective of the organobase catalyst employed, regioregular polycarbonates were obtained via ROP of monomers with ether substituents, while the backbone connectivities of polymers derived from monomers with carbonate protecting groups suffered transcarbonylation reactions, resulting in irregular backbone connectivities and broad molar mass distributions. The sulfonyl urethane-protected monomers were unable to undergo organobase-catalyzed ROP, possibly due to the acidity of the proton in urethane functionality. The thermal behaviors of polycarbonates with ether and carbonate pendant groups were investigated in terms of thermal stability and glass transition temperature (Tg). A two-stage thermal decomposition was observed when tert-butyloxycarbonyl (BOC) groups were employed as protecting side chains, while all other polycarbonates presented high thermal stabilities with a single-stage thermal degradation. Tg was greatly affected by side-chain bulkiness, with values ranging from 39 to 139 °C. These fundamental findings of glucose-based polycarbonates may facilitate the development of next-generation sustainable highly functional materials.

Synthesis and exceptional operational durability of polyaniline-inspired conductive ladder polymers.

Ladder-type structures can impart exceptional stability to polymeric electronic materials. This article introduces a new class of conductive polymers featuring a fully ladder-type backbone. A judicious molecular design strategy enables the synthesis of a low-defect ladder polymer, which can be efficiently oxidized and acid-doped to achieve its conductive state. The structural elucidation of this polymer and the characterization of its open-shell nature are facilitated with the assistance of studies on small molecular models. An autonomous robotic system is used to optimize the conductivity of the polymer thin film, achieving over 7 mS cm-1. Impressively, this polymer demonstrates unparalleled stability in strong acid and under harsh UV-irradiation, significantly surpassing commercial benchmarks like PEDOT:PSS and polyaniline. Moreover, it displays superior durability across numerous redox cycles as the active material in an electrochromic device and as the pseudocapacitive material in a supercapacitor device. This work provides structural design guidance for durable conductive polymers for long-term device operation.

Extraordinary electrochemical stability and extended polaron delocalization of ladder-type polyaniline-analogous polymers.

Electrochemical stability and delocalization of states critically impact the functions and practical applications of electronically active polymers. Incorporation of a ladder-type constitution into these polymers represents a promising strategy to enhance the aforementioned properties from a fundamental structural perspective. A series of ladder-type polyaniline-analogous polymers are designed as models to test this hypothesis and are synthesized through a facile and scalable route. Chemical and electrochemical interconversions between the fully oxidized pernigraniline state and the fully reduced leucoemeraldine state are both achieved in a highly reversible and robust manner. The protonated pernigraniline form of the ladder polymer exhibits unprecedented electrochemical stability under highly acidic and oxidative conditions, enabling the access of a near-infrared light-absorbing material with extended polaron delocalization in the solid-state. An electrochromic device composed of this ladder polymer shows distinct switching between UV- and near-infrared-absorbing states with a remarkable cyclability, meanwhile tolerating a wide operating window of 4 volts. Taken together, these results demonstrate the principle of employing a ladder-type backbone constitution to impart superior electrochemical properties into electronically active polymers.