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

利用可再生原料分布式制造化工构件，以替代不可再生的化石资源，是建设可持续发展的国内化工产业的重要长期目标。功能化分子的转化和分离，例如来自木质纤维素生物质解聚的分子，可以使用多孔固体来完成，多孔固体在温和条件下（相对较低的温度）选择性地吸附和转化它们。这些过程通常在半水溶剂体系存在的情况下进行，这些溶剂体系本身对分配、动力学和反应性有很强的影响，显著地改变了非均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体/液体界面分子行为的基本理解，这对于合理开发用于处理可再生原料的耐用非均相催化剂和良性溶剂系统至关重要。该项目的重点是了解溶剂和溶剂分子在选定的微孔和介孔材料中的共吸附性质，以产生吸附在控制速率和指导选择性方面的作用的基础知识。目的是描述和量化分子分配的程度在固液界面结合孔隙限制；探索选择性吸附的起源及其对吸附分子迁移率的影响；并将这些信息结合起来，对涉及选定的含氧有机化合物的催化反应中的溶剂效应产生新的见解。多孔材料中吸附/吸收焓的热力学测量将由传统的吸附平衡测量与等温滴定量热法相结合获得。相互作用的分子性质将使用非原位和原位固态核磁共振（NMR）来探测，以区分吸附/吸收分子和自由分子，并测量它们的相对比例和交换速率。密度泛函理论（DFT）和分子动力学（MD）模拟将用于解释分配和吸附的趋势。反应动力学将在现场记录，并与界面组成和动力学行为联系起来。将探讨催化剂孔径和骨架拓扑结构、亲疏水性、骨架外阳离子的存在、身份和密度的影响。研究生研究员将接受固液界面表征方面的培训，并将学习在热力学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获得指导并直接参与研究。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.