Biomimetic Polymer Reactor: Design And Modulation Of Novel Tandem Catalysts

Tandem catalysis is able to perform multi-step reactions in one-pot sequentially.It not only improves the efficiency of reactions significantly,but also decreases time,energy and reagents needed,which attracted the interests of lots of researchers.However,as there are always more than one active sites(catalysts)in tandem reactors,it is critical to separate different sites and ensure each step is conducted individually.Moreover,because of the complexity of the reactions involved,it is often challenging to achieve proper control over the reaction process.As we know,biological systems in nature always perform synthesis of molecules or other complex reactions efficiently as well as they are able to adjust to the change of environment perfectly.By introducing the inspirations from nature,herein,several novel catalytic reactors were proposed to address the two challenges of site separation and smart control of tandem catalysis.First of all,the goal of sites separation is achieved through an enzyme-like molecularly imprinted polymer reactor MIP-Au-NP-BNPC.Inspired by the compartmentalization of cells,two molecularly imprinted cavities(imprinted substrate:NPA and NP)were created in the active molecularly imprinted polymer PAMPS,which contained acidic sites(catalytic hydrolysis reaction)and Au nanoparticle sites(catalytic reduction reaction)respectively.The different channels of the two catalytic sites in the reactor enables different catalytic reactions to occur in different regions,resulting in the process of tandem reactions.Moreover,a related model is established based on quantum mechanics theory to clarify the separate tandem catalysis process.The second solution is a core-shell structure catalytic nanoreactor AMPS@AMAg.As a result of mass transfer and the radial distribution of reaction sites in the structure,the core-shell structure enables the nanoreactor to perform different processes of catalysis sequentially.The shell of this nanoreactor was prepared by PAM,containing Ag nanoparticles site for catalytic reduction.The core layer PAMPS containing another acidic active site is responsible for the next hydrolysis reaction.Due to the spatiotemporally separation catalysis induced by the structure of the nanoreactor,the processes will proceed without the mutual interference.In this way,the nanoreactor realized the tandem catalysis with successful site separation.Furthermore,the mass transfer and kinetics analyses were studied to explain the spatiotemporal separate tandem catalysis.After using different methods to separate the active sites efficiently,more efforts were made to reach the smart control about tandem catalysis processes.The next new type catalytic reactor is a mussel-inspired smart catalytic reactor MIP-Ag PRS.Inspired by the strong adhesion ability and the self-healing ability of mussel and related materials,a three-layer switchable tandem reactor was prepared in the experiment.The top and bottom functional layers were composed of the molecularly imprinted polymers(PAMPS and PAM)containing the different catalytic active components that are responsible for catalysis of different reactions.The smart layer in the middle was composed of mussel-inspired self-healing copolymer PDPA-PAM and acted as an intermediate switch.It is able to react to the different temperature conditions to achieve simple and tandem reactions by closing and opening the access.The change of the access would allow or inhibit the intermediate product,hence performing the selfcontrol of catalytic processes of substrates.Moreover,inspired by the response behavior of the “soft” structure in the biological system to the change of the environment,bilayer polymer reactor DPR is prepared.DPR is composed of the two different temperature-sensitive polymer layers(PAMPS-PAM layer and PVI-PTFMA-Au layer).The two functional layers are able to respond to different specific temperatures and each also contains different catalytic sites.At relatively low temperatures(<37℃),since the reaction channels in both layers are closed,the polymer reactor has almost no catalytic activity at this time.At medium temperature(37℃<T<50℃),the break of the weak hydrogen interaction in one polymer layer caused the open tunnel in this layer,resulting in the significant activity of first step of the tandem reaction.At this time,the polymer reactor is able to catalyze the simple one-step reaction.At relatively high temperatures(>50℃),the break of the stronger electrostatic interaction caused the open tunnel of another layer,performing the tandem reaction process at this time.As a result,this new type of bilayer polymer reactor achieves the smart control of the tandem reactions.Finally,the three-layer switchable polymer reactor PRS with the tandem/ simple catalytic ability was prepared.The top and bottom layers were composed of two different molecularly imprinted polymers(MIP-PAMPS and MIP-Ag PAM)respectively containing two catalytic sites(acidic site and metal nanoparticles sites),performing the selective tandem reactions without the interference.And the middle layer acted as temperature responsive switch of the tandem catalysis process.In an aqueous environment,when temperature is low(<47℃),it exhibited open access(hydrophilic condition).Then the intermediate was able to pass through,finishing the tandem processes from hydrolysis to reduction.When temperature is high(>47℃),it became a closed tunnel(hydrophobic condition),which obstructed the access of reactant.As a result,the reactor can only conduct the simple hydrolysis processes.Furthermore,the copolymer AM with different ratios was introduced to adjust the responsive temperature range,which enables more practical use.In addition,the thermal sensitivity and the repeating switchable catalytic ability were discussed to achieve the optimized catalysis.This way,the fast responsive and stable polymer reactor with self-controlled catalytic ability was prepared.Inspired by the biological system,a series of reactors were prepared by thorough and systematic research,addressing the important challenges in tandem catalysis.By preparing different kinds of new catalytic reactors,the research is able to achieve the smart control of the tandem catalysis while separating the catalytic sites effectively.The study suggests new solutions toward the challenges about the tandem catalysis,and provides inspiration of the functional polymer in complicated reaction areas.