12/30/2022 0 Comments Pickering emulsion![]() Although encouraging progress has been achieved, most of these existing biomimetic microreactors either require relatively complex fabrication procedures or lack a proper liquid medium inside their interior, leading to either difficulty in rationally controlling the interior structures or inability to enrich/sequester reactants 32. Motivated by the approach of nature in its realization, extensive efforts have been made to synthesize various biomimetic microreactors for executing cascade reactions, such as lipid vesicles 12, 13, polymersomes 14, 15, 16, 17, microcapsules 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, coacervate droplets 28, 29, and proteinosomes 30, 31. The high efficiency is in part attributed to the unique multi-level compartmentalization in cells that enables them to sequester reactants/intermediates and spatially isolate incompatible species within different organelles (sub-compartments (SCs)) 11. The living cell is an ideal model for the design of cascade catalytic microreactors as it allows multiple biocatalytic transformations to proceed very efficiently 10. An ideal cascade catalytic microreactor should meet the following requirements: (i) spatial isolation of different catalytically active sites, while still ensuring their close proximity (ii) favorable microenvironments able to channel intermediate reactants to the next catalytic sites avoiding random diffusion (iii) multiple catalysts working synergistically, and (iv) enable a long-term continuous flow process or multiple recycling of catalysts. The co-localization of multiple catalysts within microreactors is emerging as an exciting way to realize this concept with high cascade reaction efficiency but continues to be a cutting-edge research topic in that there remain many critical challenges to overcome, especially in relation to practical application to continuous flow cascade reactions 8, 9. However, these methods are still incapable of precisely controlling cascade reactions at nanoscale levels, leading to relatively low cascade reaction efficiency. The methods to realize this concept have been developed and include such techniques as physical mixing of catalytically different solid particles 6, and multi-layered beds 7. PICKERING EMULSION UPGRADEThe compartmentalization effect and enriching-reactant properties arising from the biomimetic microreactor are theoretically and experimentally identified as the key factors for boosting the catalysis efficiency and for regulating the kinetics of cascade catalysis.Ī cascade of multiple catalytic reactions in a continuous flow manner is an important concept to upgrade chemical synthesis because of its noteworthy advantages such as shortened reaction time, reduced waste generation, and avoidance of intermediate separation 1, 2, 3, 4, 5. As exemplified by two chemo-enzymatic cascade reactions for the synthesis of chiral cyanohydrins and chiral ester, 5 − 420 fold enhancement in the catalysis efficiency and as high as 99% enantioselectivity were obtained even over a period of 80 − 240 h. Our method involves co-localization of different catalytically active sub-compartments within droplets of a Pickering emulsion yielding cell-like microreactors, which can be packed in a column reactor for continuous flow cascade catalysis. ![]() Herein, a method for practical one-pot cascade catalysis is developed by combining Pickering emulsions with continuous flow. A continuous flow cascade of multi-step catalytic reactions is a cutting-edge concept to revolutionize stepwise catalytic synthesis yet is still challenging in practical applications. ![]()
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