RESUMO
Tandem catalysts with multifunctional sites can achieve high-efficiency catalytic transformations for quickly converting simple raw materials into complex value-added products. The integration of highly active species of metal nanoparticles (NPs) and single-atom catalytic sites (SACs) into one tandem system promises to synthesize an ideal bifunctional catalyst on account of the synergistic effect between NPs and SACs. However, such ideas face some challenges as deactivation or loss of active species, and low efficiency or side reactions caused by the disorder of different active species. Herein, a double-shell microencapsulated nanoreactor was fabricated as a bifunctional catalyst for the one-pot synthesis of cyclic carbonates from olefins. The microcapsules consist of an inner shell of nitrogen-doped porous carbon rich in Zn SACs, an outer shell of mesoporous SiO2, and Au NPs confined between the outer and inner shells, noted as Zn-N-C/Au@mSiO2. Particularly, two active species are spatially compartmented within microcapsules. Furthermore, the catalyst was applied in the one-pot synthesis of styrene carbonate from styrene with CO2 under normal pressure and showed admirable performance. The yield of cyclic carbonate reached 92.9% at 93.2% olefins conversion. Furthermore, the catalyst shows good reusability with little loss of catalytic performance (4.0%) even after using it 15 consecutive times. The unique structure used in this work can rationally integrate diverse catalytic species into one system and offering adequate protection, which provides an effective strategy for the development of multi-site catalysts.
RESUMO
A novel type of bi-functional microencapsulated phase change material (MEPCM) microcapsules with thermal energy storage (TES) and carbon dioxide (CO2) photoreduction was designed and fabricated. The polyaniline (PANI)/titanium dioxide (TiO2)/PCN-222(Fe) hybrid shell encloses phase change material (PCM) paraffin by the facile and environment-friendly Pickering emulsion polymerization, in which TiO2 and PCN-222(Fe) nanoparticles (NPs) were used as Pickering stabilizer. Furthermore, a ternary heterojunction of PANI/(TiO2)/PCN-222(Fe) was constructed due to the tight contact of the three components on the hybrid shell. The results indicate that the maximum enthalpy of MEPCMs is 174.7 J·g-1 with encapsulation efficiency of 77.2%, and the thermal properties, chemical composition, and morphological structure were well maintained after 500 high-low temperature cycles test. Besides, the MEPCM was employed to reduce CO2 into carbon monoxide (CO) and methane (CH4) under natural light irradiation. The CO evolution rate reached up to 45.16 µmol g-1 h-1 because of the suitable band gap and efficient charge migration efficiency, which is 5.4, 11, and 62 times higher than pure PCN-222(Fe), PANI, and TiO2, respectively. Moreover, the CO evolution rate decayed inapparently after five CO2 photoreduction cycles. The as-prepared bi-functional MEPCM as the temperature regulating building materials and air purification medium will stimulate a potential application.