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

以可再生原料作为不可再生化石资源的替代品，分布式制造化学构件是建设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，例如衍生自木质纤维素生物质解聚的那些，可以使用在温和条件（相对低的温度）下选择性吸附和转化它们的多孔固体来完成。这样的过程通常在半水性溶剂体系的存在下进行，其本身对分配、动力学和反应性产生强烈影响，显著改变了非均相催化剂在生物质转化中的有效性。该研究项目旨在对固/液界面上的分子行为有一个基本的了解，这对于合理开发用于加工可再生原料的耐用非均相催化剂和良性溶剂体系至关重要。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的共吸附性质，以便产生关于吸附在控制速率和指导选择性中的作用的基本知识。我们的目标是描述和量化的程度，结合孔限制在固液界面的分子分配;探索选择性吸附的起源和吸附的分子的流动性的后果;和联合收割机结合这些信息，以创造新的洞察溶剂的影响，涉及选定的含氧有机化合物的催化反应。热力学测量多孔材料中吸附/吸收的热力学性质将从常规的吸附平衡测量结合等温滴定量热法获得。将使用非原位和原位固态核磁共振（NMR）探测相互作用的分子性质，以区分吸附/吸收和游离分子，并测量其相对比例和交换速率。将采用密度泛函理论（DFT）和分子动力学（MD）模拟来解释分配和吸附的趋势。反应动力学将被记录在原位，并与界面组成和动态行为。催化剂孔径和框架拓扑结构，亲水性/疏水性，存在，身份和密度的框架外阳离子的影响，将进行探讨。一名研究生研究员将接受固液界面表征方面的培训，并将学习热力学和动力学测量之间的联系。该奖项反映了NSF的法定使命，并通过使用基金会的智力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.