Nanoscale Filming of Solid Catalysts
Abstract
Solid catalysts are at the heart of many chemical processes. They are not only responsible for the production of fuels, chemicals, and materials, but also find widespread application in environmental protection and pollution control. Determining the active site of real-life solid catalysts and elucidating their reaction mechanism remains an intellectual challenge. It is of paramount importance for new roads towards more effective and selective solid catalysts. Unfortunately, in most cases, the rational design still remains a pipe dream and as of today, the experimental tools available for monitoring catalysts as they work are still, in the main, too rudimentary to accomplish this ambitious goal. Some of the questions out here are: "How can we push the spatial and temporal resolution of spectroscopy and microscopy so we can make detailed molecular movies of a catalytic solid at work?" Here the envisaged "camera" should not only capture nanoscale snapshots of the organic or inorganic part of a catalytic process; but of both worlds, as it is the interplay between both parts of chemistry which will ultimately lead to the mastering of chemical reactivity. It is exactly this what we want to accomplish in this research project. In this ambitious 3-year project, we aim to make molecular movies of well-structured porous catalysts down to the level of a single particle with nanoscale resolution and single molecule sensitivity. We have therefore selected the acid-catalyzed hydrolysis of fluorescent esters as a sensitive probe. By doing so we will capture all the dynamic features starting from the transport phenomena of the fluorescent ester molecule and the resulting reaction products in the macro-mesa-micro-space of the catalyst particle up to the breaking of ester bond of the probe molecule at the catalyst surface. This will be accomplished by a two-pronged approach. First, we will use inorganic synthesis routes to make porous structured materials in which both the size and orientation of micro-, mesa- and macropores are varied in a systematic manner, along with their chemical composition. By selectively positioning acid sites in these structured porous materials we have access to a unique set of porous solid catalysts. With the aid of a combination of advanced electron and X-ray characterization methods, we can then determine the internal porous structure and establish so-called "street maps" in 3-D for these materials. Second, we will synthesize a set of fluorescent ester molecules, which can be followed by single-molecule fluorescence microscopy, both during transport and reaction. These molecules have different sizes, polarity, and reactivity; and by combining them with the set of porous solid catalysts we are able to fundamentally study the processes of transport, mobility, and reactivity down to the level of a single catalyst particle. In a third part of the work, we will develop and apply a high-throughput screening method, based on inkjet printing technology and employing the developed fluorescent probe molecules and structured catalyst particles, to select the most active material and reaction conditions for the acid-catalyzed hydrolysis of the fluorescent ester molecules. Based on the developed methods, materials and approaches we will be able to fundamentally investigate chemical reactions on surfaces and determine a unique set of physical insights and knowledge not accessible so far with any methodology. The developed experimental approaches may find also applications in research on inorganic membranes, adsorbents, fuel cells as well as batteries.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 14, 2019
- Source ID
- W911NF1810284
Entities
People
- Bert Weckhuysen
Organizations
- Army Contracting Command
- United States Army
- Utrecht University