Quantifying adsorption-diffusion-reaction of biomass-derived molecules at solid-liquid interfaces

用可再生原料分散生产化学原料，作为不可再生化石资源的替代品，是建立可持续国内化学工业的一个重要长期目标。功能化分子的转化和分离，例如那些来自木质纤维生物质解聚的分子，可以使用在温和的条件下(相对较低的温度)选择性地吸附和转化它们的多孔固体来完成。这类过程通常是在半水溶剂体系中进行的，这些体系本身对分配、动力学和反应活性产生了强烈的影响，显著改变了多相催化剂在生物质转化中的有效性。该研究项目旨在发展对固/液界面分子行为的基本了解，这对于合理开发用于加工可再生原料的耐用多相催化剂和良性溶剂系统是至关重要的。该项目侧重于了解溶剂和溶剂分子在选定的微孔和介孔材料中共吸附的性质，以便产生关于吸附在控制速率和指导选择性方面的作用的基础知识。其目的是描述和量化分子在固液界面上分配的程度以及孔限制；探索选择性吸附的起源和对吸附分子迁移率的影响；并结合这些信息对涉及特定含氧有机化合物的催化反应中的溶剂效应产生新的洞察。通过常规的吸附平衡测量结合等温滴定量热法，可以得到多孔材料中吸附/吸附热焓的热力学测量。我们将使用非原位和原位固体核磁共振来探索相互作用的分子性质，以区分吸附/吸收的分子和自由分子，并测量它们的相对比例和交换率。将使用密度泛函理论(DFT)和分子动力学(MD)模拟来解释分配和吸附的趋势。反应动力学将被现场记录下来，并与界面组成和动态行为联系起来。考察了催化剂孔径大小和骨架拓扑结构、亲水性/疏水性、骨架外阳离子的存在、识别和密度等因素对催化剂性能的影响。一名研究生研究人员将接受固液界面表征方面的培训，并将学习如何在热力学测量和动力学测量之间建立联系。来自代表性不足群体的本科生将接受指导并直接参与研究。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Distributed manufacturing of chemical building blocks from renewable feedstocks as an alternative to non-renewable fossil resources is an important long-term goal in building a sustainable domestic chemical industry. Transformations and separations of functionalized molecules, such as those derived from depolymerization of lignocellulosic biomass, can be accomplished using porous solids that selectively adsorb and convert them under mild conditions (relatively low temperatures). Such processes are usually conducted in the presence of semi-aqueous solvent systems, which themselves exert strong effects on partitioning, dynamics, and reactivity, significantly altering the effectiveness of heterogeneous catalysts in biomass conversion. The proposed research project aims at developing a fundamental understanding of molecular behavior at solid/liquid interfaces, which is essential for the rational development of durable heterogeneous catalysts and benign solvent systems for processing renewable feedstocks.The project focuses on understanding the nature of the co-adsorption of solvent and solvent molecules in selected microporous and mesoporous materials, in order to generate fundamental knowledge about the role of adsorption in controlling rates and directing selectivity. The objective is to describe and quantify the extent of molecular partitioning at solid-liquid interfaces in conjunction with pore confinement; explore the origins of selective adsorption and consequences for mobility of adsorbed molecules; and combine this information to create new insight into solvent effects in catalytic reactions involving selected oxygenated organic compounds. Thermodynamic measurements of enthalpies of adsorption/absorption in porous materials will be obtained from conventional adsorption equilibrium measurements in combination with isothermal titration calorimetry. The molecular nature of the interactions will be probed using both ex-situ and in-situ solid state Nuclear Magnetic Resonance (NMR) to distinguish between adsorbed/absorbed and free molecules, and to measure their relative proportions and rates of exchange. Density Functional Theory (DFT) and Molecular Dynamics (MD) simulations will be employed to interpret trends in partitioning and adsorption. Reaction kinetics will be recorded in situ and linked to interfacial composition and dynamic behavior. The effect of catalyst pore size and framework topology, hydrophilicity/hydrophobicity, the presence, identity, and density of extra-framework cations, will be explored. A graduate student researcher will be trained in the characterization of solid-liquid interfaces and will learn to make connections between thermodynamic and kinetic measurements. Undergraduate students from under-represented groups will receive mentoring and participate directly in the research.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.