Fabrication of multi-compartmentalized mesoporous silica microspheres through a Pickering droplet strategy for enhanced CO2 capture and catalysis

It is a long-standing dream to fabricate micron-sized inorganic spheres that have nanocompartments enclosed by a permeable shell and thus resemble the shape of natural cells. Here, we demonstrate a novel synthesis protocol to attain this goal for the first time. This protocol unprecedentedly harnesses interfacial sol–gel growth around Pickering droplets coupled with a surfactant assembly-directed sol–gel process within droplet-confined spaces. This protocol enables us to fabricate novel mesoporous silica microspheres (MSMs) with tunable interior architectures, such as hollow MSMs, hollow nanosphere-containing MSMs (hn@MSMs), nanosphere-containing MSMs (n@MSMs), yolk-shell-structured MSMs (y@MSMs) and “solid” MSMs. The obtained multi-compartmentalized MSMs exhibit good permeability to external molecules and good mechanical strength against stress. Moreover, their structural features benefit practical applications of CO2 capture and enzymatic reactions. Due to the high dispersion of tetraethylenepentamine and enzyme in the spatially separated nanocompartments, the developed CO2 sorbents and catalysts exhibit significantly enhanced CO2 capture efficiency and catalysis efficiency. Meanwhile, owing to the encapsulation of these nanocompartments inside the hollow micron-sized spheres, these CO2 sorbents and catalysts can be packed directly in fixed-bed reactors, which is unattainable for nanoparticle materials. A synthetic protocol that introduces nanoscale chambers into glassy microbeads shows promise for catalytic reactions and carbon dioxide capture. Attempts to fabricate compounds that resemble artificial cells often result in structurally weak materials with poorly defined compartments. Hengquan Yang and colleagues from Shanxi University in Taiyuan, China, have used water-in-oil emulsions stabilized by nanoparticles to produce a variety of rigid cell-like structures. Their approach uses silica nanospheres to cover the surfaces of water droplets and act as templates for the growth of mechanically tough shells. By changing the amounts of surfactant, base and siliceous precursors, the team produced silica structures that ranged from microscale hollow beads to structures with tiny spherical nano-compartments. The latter proved effective at dispersing catalytic enzymes and absorbing CO2 throughout its porous microstructure. A novel synthesis protocol for fabrication of micron-sized multi-compartmentalized mesoporous silica spheres is developed, which is exemplified by successful synthesis of a family of unprecedented multi-compartmentalized mesoporous silica microspheres (MSMs) including hollow MSMs, hollow nanosphere-containing MSMs, nanosphere-containing MSMs, yolk-shell-structured MSMs, and “solid” MSMs. These microspheres exhibit not only significantly enhanced performances in CO2 capture and catalysis but also the superiority in technical applications.