Synthesis of All-Benzene Multi-Macrocyclic Nanocarbons via Post-Functionalization of meta-Cycloparaphenylenes.

Expanding the diversity of multi-macrocyclic nanocarbons, particularly those with all-benzene scaffolds, represents intriguing yet challenging synthetic tasks. Complementary to the existing synthetic approaches, here we report an efficient and modular post-functionalization strategy employing iridium-catalyzed C-H borylation of the highly strained meta-cycloparaphenylenes (mCPPs) and an mCPP-derived catenane. Based on the functionalized macrocyclic synthons, a number of novel all-benzene topological structures including linear and cyclic chains, polycatenane, and pretzelane have been successfully prepared and characterized, thereby showcasing the synthetic utility and potential of the post-functionalization strategy.

Modular Synthesis of Improbable Rotaxanes with All-Benzene Scaffolds.

"Improbable" rotaxanes consisting of interlocked conjugated components represent non-trivial synthetic targets, not to mention those with all-benzene scaffolds. Herein, a modular synthetic strategy has been established using an isolable azo-linked pre-rotaxane as the core module, in which the azo group functions as a tracelessly removable template to direct mechanical bond formations. Through versatile connections of the pre-rotaxane and other customizable modules, [2]- and [3]rotaxanes derived from all-benzene scaffolds have been accomplished, demonstrating the utility and potential of the synthetic design for all-benzene interlocked supramolecules.

A Conjugated Covalent Template Strategy for All-Benzene Catenane Synthesis.

Mechanically interlocked molecules based on oligoparaphenylene-derived nanohoops, particularly those without heteroatoms, are synthetically challenging and topologically intriguing targets. Herein, a π-conjugated covalent template strategy based on azo group has been developed, which features dual intramolecular macrocyclizations directed by a tetra-substituted azobenzene core, followed by traceless removal of the azo linker. Employing this strategy, the efficient synthesis of a novel all-benzene [2]catenane consisting of meta-cycloparaphenylenes has been accomplished.

Preparation of Surfactant-Free Nano Oil Particles in Water Using Ultrasonic System and the Mechanism of Emulsion Stability.

Emulsion technology is widely used in the preparation of cosmetics, pharmaceuticals, drug delivery, and other daily necessities, and surfactants are frequently used to prepare these emulsions because of the lack of reliable surfactant-free emulsification techniques. This is disadvantageous because some surfactants pose health hazards, cause environmental pollution, have costly components, and place limitations on process development. In this paper, an efficient method for surfactant-free nano-emulsification is presented. In addition, we discuss the effects of different operating parameters on the oil particle size, as well as the effect of the particle size on the emulsion stability. Specifically, we compared three surfactant-free ultrasonic emulsification technologies (horn, bath, and focused ultrasonic systems). The focused ultrasonic system, which concentrates sound energy at the center of the dispersion system, showed the best performance, producing emulsions with a particle size distribution of 60-400 nm at 400 kHz. In addition, phase separation did not occur despite the lack of surfactants and thickeners, and the emulsion remained stable for seven days. It is expected to be widely used in eco-friendly emulsification processes.

pKa-Directed Incorporation of Phosphonates into MOF-808 via Ligand Exchange: Stability and Adsorption Properties for Uranium.

We report a class of pKa-directed, precise incorporation of phosphonate ligands into a zirconium-based metal-organic framework (Zr-MOF), MOF-808, via ligand exchange. By replacing of formate ligands with methylphosphonic acid (MPA), ethanephosphonic acid (EPA), and vinylphosphonic acid (VPA), whose pKa values are slightly higher than that of the benzenetricarboxylic acid (BTC) linker in MOF-808, daughter MOFs can be synthesized without controlling the stoichiometric amounts of added MPA. The methylphosphonate MOFs (808-MPAs) demonstrate high porosities, with only small changes in the pore diameter and specific surface area when compared with the parent MOF-808. PXRD patterns and structure refinements indicate the expansion of the lattice for all MOFs after decorating with methylphosphonate ligands. The XPS spectra reveal a charge redistribution of the Zr6 node after ligand exchange. FTIR and 31P MAS NMR spectra, combined with DFT calculation, suggest that the methylphosphonate ligand is connected to the Zr6 node as CH3P(O)(OZr)(OH) species with an accessible acidic P-OH group. Besides, 808-MPAs demonstrate excellent chemical stability in concentrated HCl, concentrated HNO3, hot water, and 0.2 mol/L trifluoroacetic acid solutions. Impressively, 808-MPAs show ultrafast adsorption performance for uranyl ions using the ion-exchange property of P-OH sites in their cavity environment, with an equilibrium time of 10 min, much quicker than the previous adsorbents. The present study demonstrates a series of important proof-of-concept examples of the pKa-directed Zr-MOFs with tunable phosphonate-terminated ligands, which can extend to other phosphonate-functionalized Zr-based framework platforms in the near future.