Radical-containing Porous Organosilica Host Phases Studied by Advanced Electron Paramagnetic Resonance Techniques

本项目旨在利用先进的电子顺磁共振（EPR）技术研究一类新的功能纳米结构材料——多孔有机二氧化硅相，包括具有稳定自由基修饰的周期性介孔有机二氧化硅（PMO）。这种有机二氧化硅相作为小分子（包括气体）的潜在稳健吸附剂引起了人们的广泛关注，并且使用附着在介孔材料表面的稳定自由基增强了它们的功能特性。同时，这些顺磁掺杂剂是极好的EPR信号分子。特别是，其他顺磁性和反磁性分子在多孔有机二氧化硅宿主相中的吸附、稳定自由基的作用以及与它们的相互作用具有实际意义。在本项目中，我们提出了新的自由基标记多孔有机二氧化硅主体相的合成，其物理化学性质和广泛的结构和功能研究的EPR。首先，用连续波和脉冲多频EPR表征裸体材料中自由基的附着模式及其局部环境。接下来，将详细研究各种客体分子的吸附和解吸，包括一氧化氮（NO）、二氧化氮（NO2）、挥发性自由基（TEMPO）等。我们的目标是深入了解客体分子与有机二氧化硅相孔隙中各种自由基位点之间的相互作用，并阐明吸附的机制方面。这些信息可以通过应用先进的脉冲EPR方法获得，如ENDOR（电子-核双共振）、HYSCORE（超精细亚能级相关光谱）、DEER/PELDOR（双电子-电子共振）等。该项目将对多孔有机硅基质相中自由基中心的局部结构和功能进行详细的了解。这将有力地帮助开发进一步的策略，以定向设计这种用于气体分离、储存、传感、催化和其他潜在应用的自由基修饰多孔材料。

This project is aimed at investigation of a new family of functional nanostructured materials – porous organosilica phases, including periodic mesoporous organosilica (PMO), decorated with stable radicals – using advanced Electron Paramagnetic Resonance (EPR) techniques. Such organosilica phases attract a lot of attention as prospective robust sorbents for small molecules, including gases, and the use of stable radicals attached to the surface of mesoporous materials enhances their functional properties. At the same time, these paramagnetic dopants are excellent signalling molecules for EPR. In particular, adsorption of other paramagnetic and diamagnetic molecules in porous organosilica host phases and the role of stable radicals and interaction with them are of practical interest. Within this project, we propose the synthesis of new radical-labeled porous organosilica host phases, their physicochemical characterization and extensive structural and functional study by EPR. First of all, radical attachment modes and their local surrounding in bare materials will be characterized by continuous wave and pulse multifrequency EPR. Next, adsorption and desorption of various guest molecules including nitric oxide (NO), nitrogen dioxide (NO2), volatile radicals such as TEMPO and others, will be studied in detail. We aim at in-depth understanding of interactions between guest molecules and various radical sites in the pores of organosilica phases, and on elucidation of mechanistic aspects of adsorption. This information becomes available via application of advanced pulse EPR methods such as ENDOR (Electron-Nuclear Double Resonance), HYSCORE (Hyperfine Sublevel Correlation Spectroscopy), DEER/PELDOR (Double Electron-Electron Resonance), etc. The detailed understanding of local structure and function of radical centers in porous organosilica host phases is anticipated as a result of proposed project. This will strongly aid in developing further strategies for directed design of such radical-decorated porous materials for gas separation, storage, sensing, catalytic and other potential applications.