Study on Catalytic Reactions in 3D-Continuous Nanoporous Membrane-based Nanoreactors Loaded with Metal Nanoparticles or Enzymes

Abstract

In this thesis, we present an efficient catalytic membrane nanoreactor prepared by incorporating metal nanoparticles (MNPs) or enzymes within a 3D-continuous nanopore. Homogeneous adsorption of metal precursor onto polymer-coated nanoporous channel and subsequent reduction generated ultrafine MNPs with adjustable size, loading amount, and distribution.by varying metal precursor and reducing agent concentrations. The flexibility in regulating metal loadings and sheet sizes enhances the scalability of catalyst quantity, making the membranes suitable for both batch and continuous flow catalytic reactions with exceptional stability over multiple long-term reuses. In addition, we expand the effectiveness of MNP-loaded membrane to selective catalysis of alkyne in liquid phase, a great challenge requiring high selectivity of alkene with almost full conversion. To control the catalytic selectivity in liquid phase, we considered the microenvironment of various components (e.g., solvent, reactant, and polymer brush) surrounding MNPs by investigating the adsorption strengths of alkyne and alkene molecules in liquid phase. The in situ-grafted polymer brushes on nanopore walls of membrane induces the preferential accumulation of alkyne over corresponding alkene, thereby facilitating the transport near the surface of MNPs. Consequently, liquid-phase selective hydrogenation of alkyne using modified nanoreactors show high catalytic performance under both batch and continuous flow conditions. In addition, solvent-dependent adsorption capacity/selectivity of alkyne and alkene onto the membranes can affect the liquid phase catalytic performance. This predictive understanding of thermodynamics in the liquid phase can guide solvent selection for future liquid phase catalytic reactions. The following study shows the enzyme-loaded nanoreactors for selective formation of macrocycles within the confined nanoporous channel. Taking advantage of the 3D-continuous nanoporous channel and integration reaction and separation in a single operation, it allows for the constrictive conformation of linear monomers into the confined nanovolume. To synthesize the enzyme membrane reactor, we entrapped the enzyme into the nanopores by simply passing enzyme feed solution through the nanoporous membrane. We examined its biocatalytic performance in macrocyclization to form macrocycle product. The entrapped enzyme exhibited high selectivity for macrocycles with exceptional thermal and structural stability. These overall findings highlight the potential of 3D-continuous nanoporous membrane as a useful platform for stabilization MNPs or enzymes for catalytic nanoreactors, maximizing the productivity and selectivity of catalytic process.