Synthesis of Single-Layer Two-Dimensional Metal-Organic Frameworks M3 (HAT)2 (M=Ni, Fe, Co, HAT=1,4,5,8,9,12-hexaazatriphenylene) Using an On-Surface Reaction

Palladium-anchored calix[4]arene-derived porous organic polymer towards efficient hydrolytic cleavage of carbon disulfide

The release of carbon disulfide can have adverse effects on our environment and human health. The stability of carbon disulfide and the slow kinetics of hydrolysis can make it challenging to achieve efficient and practical cleavage of the CS bonds. Herein, a calix[4]arene-based porous organic polymer (CPOP-1) is innovatively synthesized through an optimized polycondensation reaction using C-Methylcalix[4]resorcinarene and hexafluoro-hexaazatriphenylene as monomers. Subsequently, palladium-induced calix[4]arene-based porous organic polymer was also synthesized via strong Pd-N coordination bonds to construct the metal-induced porous catalyst (CPOP-2). The polymeric catalyst active center [Pd2+(N^N)(NO3-)2] demonstrated outstanding catalytic hydrolysis performance (11.14 μmol g-1 h-1) in 10.5 h which is significantly enhanced by ca.13.2 times as compared to reported mononuclear Bpy-Pd(NO3)2, and 7.07 times than model trinuclear complex catalyst HATN-Pd-1, respectively. The control experiments revealed that POP catalysts showcased robust stability, prolonged effectiveness, and feasible recyclability during the hydrolytic cleavage of carbon disulfide at room temperature in aqueous solutions. Furthermore, the coordination environment of [Pd2+(N^N)] was validated through XPS, EXAFS, and isotope labeling measurements, and the hydrolysis cleavage products were confirmed e. g. CO2, sulfide, and protons. More importantly, a reaction mechanism was formulated coupled with theoretical calculations, and simulations. The proposed mechanism involves sequential OH- nucleophilic attacks on the carbon atoms of insert-coordinated CS2 and COS, leading to the cleavage of double CS bonds and the formation of CO bonds. The concurrent dissociation of the C-S bond and liberation of CO2 result in an intermediate structure characterized by [(N^N)Pd2+](SH-)2. This intermediate motif serves as the source of the thermodynamic driving force for the reaction.

Order-Disorder Transition of Two-Dimensional Molecular Networks through a Stoichiometric Design

Materials with disordered structures may exhibit interesting properties. Metal-organic frameworks (MOFs) are a class of hybrid materials composed of metal nodes and coordinating organic linkers. Recently, there has been growing interest in MOFs with structural disorder and the investigations of amorphous structures on surfaces. Herein, we demonstrate a bottom-up method to construct disordered molecular networks on metal surfaces by selecting two organic molecule linkers with the same symmetry but different sizes for preparing two-component samples with different stoichiometric ratios. The amorphous networks are directly imaged by scanning tunneling microscopy under ultrahigh vacuum with a submolecular resolution, allowing us to quantify its degree of disorder and other structural properties. Furthermore, we resort to molecular dynamics simulations to understand the formation of the amorphous metal-organic networks. The results may advance our understanding of the mechanism of formation of monolayer molecular networks with structural disorders, facilitating the design and exploration of amorphous MOF materials with intriguing properties.

High-Throughput Preparation of Supramolecular Nanostructures on Metal Surfaces

One of the contemporary challenges in materials science lies in the rapid materials screening and discovery. Experimental sample libraries can be generated by high-throughput parallel synthesis to map the composition space for rapid material discoveries. Molecular self-assembly on surfaces has proved a useful way to construct nanostructures with interesting topologies or properties. Despite the strong dependence of molecular stoichiometry on the structures, high-throughput preparations of supramolecular surface nanostructures have been far less explored. Here, by integrating a physical mask into the standard ultra-high-vacuum (UHV) molecular preparation system we show a high-throughput approach for preparing supramolecular nanostructures of continuous composition spreads on metal surfaces. The spatially addressable sample libraries of supramolecular self-assemblies are characterized by high-resolution scanning probe microscopy. We could explore different binary nanostructures of varying molecular ratios on one single substrate. Moreover, we use the minimum spanning tree approach to qualitatively and quantitatively study the structural properties of the formed nanostructures. This high-throughput approach may accelerate the screening and exploration of surface-supported, low-dimensional nanostructures not limited to supramolecular interactions.