SMARTMIP · Modulated Catalysis by Smart Molecularly Imprinted Polymers

Modulated Catalysis by Smart Molecularly Imprinted Polymers

The emerging challenge associated with the increasing demands of controllable chemical reactions has fuelled an urgent need for new methodologies to develop tailor-made catalytic materials. As a result of recent intense research effort, a large body of knowledge in this field is now available; however, most of this cannot provide a simple, predictable and straightforward design for tailor-made catalytic materials. A generic protocol suitable for the development of a new generation of tailor-made catalytic materials is urgently needed. The objective of this MC-IIF project was to tackle this challenge and to develop knowledge and expertise in the creation of a new generation of tailor-made catalytic materials. Dubbed a 'key-to-lock' technology, molecular imprinting provides a core solution to overcome the limitations of current catalytic materials. By integrating molecular imprinting with synthetic catalysts, we have successfully developed smart molecularly imprinted polymers (MIPs) capable of modulated catalysis (as shown in Scheme 1). These smart MIPs were capable of highly selective catalysis at relatively low temperatures, while exhibiting only marginal catalysis at higher temperatures. In this way, chemical processes catalysed by the smart MIPs demonstrated an 'on/off'-switchable model. Four specified work packages, each comprising a number of tasks, were completed during the tenure of this fellowship. UV spectra were used to optimise the template-monomer interaction in the first work package. The template NPP was titrated into VI, leading to a shift in the spectra. The shift became maximal when the titrated NPP reached a critical amount (corresponding to 1.67 mol/mol VI/NPP ratio). In this context, a series of MIPs in both the presence and the absence of PNIPAm were prepared. Modern methods and instruments including FTIR, SEM, TEM, DCV, DLS TPD, etc were subsequently used to characterise these prepared MIPs (i.e., work package 2). Major properties, especially the imprinting-related properties, including morphology, stability, binding sites, hydrophilicity/hydrophobicity, and the 'imprint'-substrate interactions have been characterised. With a batch format, catalytic properties of these prepared MIPs were tested in the third package. At a relatively low temperature (such as 20 oC), these smart MIPs were capable of highly selective catalysis. In contrast, at higher temperatures (such as 40oC), these MIP demonstrated only marginal catalysis. The reactivity of the MIPs did not appear to significantly decrease after a series of 'on/off'-switched catalysis. These MIPs thus have the potential for practical applications. The self-switching behaviour was further determined in Package 4. By using a DCV device, the prepared MIPs, pre-absorbed with ca. 1 μmol template, were placed into a cuvette encircled by a diffusion-eliminated sonication apparatus. The transiently desorbed template was rapidly scanned by the workstation. The result indicated that the self-switching ability is a result of the access-regulated interactions. The thermal phase transition led to the alterable access for the substrate to the imprinted networks, which thereby enabled the modulated catalysis.

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