Noncovalent Grafting of Molecular Complexes to Solid Supports by Counterion Confinement

Grafting molecular complexes on solid supports is a facile strategy to synthesize advanced materials. Here, we present a general and simple method for noncovalent grafting on charge-neutral surfaces. Our method is based on the generic principle of counterion confinement in surface micropores. We demonstrate the power of this approach using a set of three platinum complexes: Pt1 (Pt1L4(BF4)2, L = p-picoline), Pt2 (Pt2L4(BF4)4, L = 2,6-bis(pyridine-3-ylethynyl)pyridine), and Pt12 (Pt12L24(BF4)24, L = 4,4′-(5-methoxy-1,3-phenylene)dipyridine). These complexes share the same counterion (BF4–) but differ vastly in their size, charge, and structure. Imaging of the grafted materials by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) and energy-dispersive X-ray (EDX) showed that our method results in a homogeneous distribution of both complexes and counterions. Nitrogen sorption studies indicated a decrease in the available surface area and micropore volume, providing evidence for counterion confinement in the surface micropores. Following the adsorption of the complexes over time showed that this is a two-step process: fast surface adsorption by van der Waals forces was followed by migration over the surface and surface binding by counterion confinement. Regarding the binding of the complexes to the support, we found that the surface–adsorbate binding constant (KS) increases quadratically with the number of anions per complex up to KS = 1.6 × 106 M–1 equaling ΔG°ads = −35 kJ mol–1 for the surface binding of Pt12. Overall, our method has two important advantages: first, it is general, as you can anchor different complexes (with different charges, counterions, and/or sizes); second, it promotes the distribution of the complexes on the support surface, creating well-distributed sites that can be used in various applications across several areas of chemistry

Isocyanate-free Polyurea Synthesis via Ru-Catalyzed Car-bene Insertion into the N‒H Bonds of Urea

Polyureas have widespread applications due to their unique material properties. Due to the toxicity of isocyanates, sus-tainable isocyanate-free routes to prepare polyureas is a field of active research. Current routes to isocyanate-free poly-ureas focus on constructing the urea moiety in the final polymerizing step. In this study we present a new isocyanate-free method to produce polyureas by Ru-catalyzed carbene insertion into the N‒H bonds of urea itself in combination with a series of bis-diazo compounds as carbene precursors. The mechanism was investigated by kinetics and DFT studies, re-vealing the rate determining step to be nucleophilic attack of a Ru-carbene moiety by urea. This study paves the way to use transition-metal catalyzed reactions in alternative routes to polyureas

High‐Rate Alkaline Water Electrolysis at Industrially Relevant Conditions Enabled by Superaerophobic Electrode Assembly

Abstract Alkaline water electrolysis (AWE) is among the most developed technologies for green hydrogen generation. Despite the tremendous achievements in boosting the catalytic activity of the electrode, the operating current density of modern water electrolyzers is yet much lower than the emerging approaches such as the proton‐exchange membrane water electrolysis (PEMWE). One of the dominant hindering factors is the high overpotentials induced by the gas bubbles. Herein, the bubble dynamics via creating the superaerophobic electrode assembly is optimized. The patterned Co‐Ni phosphide/spinel oxide heterostructure shows complete wetting of water droplet with fast spreading time (≈300 ms) whereas complete underwater bubble repelling with 180° contact angle is achieved. Besides, the current collector/electrode interface is also modified by coating with aerophobic hydroxide on Ti current collector. Thus, in the zero‐gap water electrolyzer test, a current density of 3.5 A cm−2 is obtained at 2.25 V and 85 °C in 6 m KOH, which is comparable with the state‐of‐the‐art PEMWE using Pt‐group metal catalyst. No major performance degradation or materials deterioration is observed after 330 h test. This approach reveals the importance of bubble management in modern AWE, offering a promising solution toward high‐rate water electrolysis