Polyhedral Oligomeric Silsesquioxane (POSS) Chemistry

中文版本 / Chinese version: POSS 二氟硼光催化剂：硫醚选择性氧化制亚砜 | 日本語版 / Japanese version: 日本語 The publication titled “Polyhedral oligomeric silsesquioxane difluoroboron complexes as cooperative octo-site catalysts for the photooxidation of sulfides to sulfoxides” by Mateusz Janeta and Sławomir Szafert, published in Inorganic Chemistry Frontiers on April 17, 2025, presents a study on the development of novel metal-free photocatalysts. These catalysts are based on polyhedral oligomeric silsesquioxanes (POSS) functionalized with difluoroboron complexes. Scheme 1. Synthesis of POSS-sal-BF 2 , POSS- tert -BF 2 , and POSS-npht-BF 2 . Isolated yields in parentheses.

中文版本 / Chinese version: POSS 八亚胺倍半硅氧烷：晶体结构与热性能 Four novel octa-imine-functionalized polyhedral oligomeric silsesquioxane (POSS) derivatives, designated POSS-6 through POSS-9 , have been reported by Mateusz Janeta and Sławomir Szafert in the Journal of Molecular Structure in 2025. These compounds were obtained by modular Schiff base condensation of octa(3-aminopropyl)silsesquioxane hydrochloride with the appropriate aromatic aldehyde in isolated yields ranging from 84 to 92 percent without chromatographic purification, and their structures were fully established by single-crystal X-ray diffraction. The identity of the peripheral substituent (hydroxyphenyl, bromophenyl, thiophene, or dibenzofuran) was found to govern both the non-covalent interaction topology in the solid state and the thermal behavior, with T 5% decomposition onset temperatures spanning from 305 to 326 °C across the four derivatives.

The publication titled “Zinc Imine Polyhedral Oligomeric Silsesquioxane as a Quattro-Site Catalyst for the Synthesis of Cyclic Carbonates from Epoxides and Low-Pressure CO 2 ” by Mateusz Janeta et al., published in Chemistry – A European Journal in 2020, describes the first structurally characterized polyhedral oligomeric silsesquioxane (POSS) that anchors more than one metal cation through its organic side arms. The tetranuclear zinc imine-POSS complex Zn 4 @POSS-1 converts styrene oxide into styrene carbonate with 96% conversion in four hours at only 1 atm of CO 2 , eliminating the high carbon dioxide pressures that normally accompany this transformation. The four zinc centers act cooperatively rather than independently, and the catalyst tolerates five consecutive runs with conversion falling only from 99% to 90%.

Imine-POSS nanobuilding blocks for supramolecular hybrid materials, synthesized and structurally characterized by Janeta et al. at the University of Wrocław and published in Dalton Transactions in 2016, constitute the first complete series of fully octa-imino-functionalized polyhedral oligomeric silsesquioxane (POSS) compounds, with five single-crystal X-ray diffraction structures reported for the first time. The five compounds bearing phenyl, 4-bromophenyl, 4-nitrophenyl, 2-hydroxyphenyl, and 2-naphthyl groups form three-dimensional supramolecular networks governed by halogen bonds, CH⋅⋅⋅N contacts, and intramolecular hydrogen bonds. The 4-nitrophenyl derivative assembles a porous framework whose guest-accessible channels occupy approximately 20% of the unit cell volume, extending the structural diversity first established for the octa-imine POSS derivatives POSS-6 through POSS-9 .

A study published in ACS Applied Materials & Interfaces introduces Porous Silsesquioxane–Imine Frameworks (PSIFs) — a novel class of hybrid porous aerogels synthesized from octa(3-aminopropyl)silsesquioxane (OAS-POSS) and multitopic aldehydes. Among the series, PSIF-1a achieves an I 2 vapor uptake of 485 wt%, representing the highest adsorption capacity reported to date for a solid-state adsorbent of this type. Schematic representation of the synthesis of PSIF-1–5 and I 2 vapor adsorption isotherms for PSIF-1a through PSIF-5a.