Huaixia Zhao

Space cooling and heating currently result in huge amounts of energy consumption and various environmental problems. Herein, a switching strategy is described for efficient energy-saving cooling and heating based on the dynamic cavitation of silicone coatings that can be reversibly and continuously tuned from a highly porous state to a transparent solid. In the porous state, the coatings can achieve efficient solar reflection (93%) and long-wave infrared emission (94%) to induce a subambient temperature drop of about 5 °C in hot weather (≈35 °C). In the transparent solid state, the coatings allow active sunlight permeation (95%) to induce solar heating to raise the ambient temperature from 10 to 28 °C in cold weather. The coatings are made from commercially available, cheap materials via a facile, environmentally friendly method, and are durable, reversible, and patternable. They can be applied immediately to various existed objects including rigid substrates.

Earthworms are able to pass through sticky soil without inducing stains through a self-forming thick lubricating layer on their rough skins. To mimic this earthworm-like lubricating capability, an attempt to create a textured structure on the surface of liquid-releasable polymer coatings by a "breath figure" process is described herein. The resulting coatings exhibit fast and site-specific release behavior under external triggers such as solid-based friction. The released oil is then stabilized by the surface texture to form thick lubricating layers, reducing friction and enhancing wear resistance. Moreover, the coatings also exhibit excellent antifouling property in a sticky soil environment. Because the lubricating layer can be regenerated after consumption, the potential of this self-replenished lubricating mechanism in preparing friction-reduction, antiwear, and antifouling coatings used in solid-based environments is therefore envisioned.

Two click-based porous organic polymers (CPP-1 and CPP-2) are readily synthesized through a click reaction. Using CPP-1 and CPP-2 as supports, palladium nanoparticles (NPs) with uniform and dual distributions were prepared through H2 and NaBH4 reduction routes, respectively. Ultrafine palladium NPs are effectively immobilized in the interior cavities of polymers. The coordination of 1,2,3-triazolyl to palladium and the confinement effect of polymers on palladium NPs are verified by solid-state (13)C NMR and IR spectra, XPS analyses, EDX mapping, and computational calculation. The steric and electronic properties of polymers have a considerable influence on the interaction between polymers and palladium NPs, as well as the catalytic performances of NPs. The ultrafine palladium NPs with uniform distribution exhibit superior stability and recyclability over palladium NPs with dual distributions and palladium on charcoal in the hydrogenation of nitroarenes, and no obvious agglomeration and loss of catalytic activity were observed after recycling several times. The excellent performances mainly result from synergetic effects between palladium NPs and polymers.

Two 1,2,3-triazolyl-containing porous organic polymers (CPP-C and CPP-Y) were readily synthesized through click reaction and Yamamoto coupling reaction, respectively. The effects of synthetic methods on the structures and properties of CPP-C and CPP-Y were investigated. Their chemical compositions are almost identical, but their physical and texture properties are different from each other. Ultrafine palladium nanoparticles can be effectively immobilized in the interior cavities of CPP-C and CPP-Y. The interactions between polymers and palladium are verified by IR, solid-state NMR, XPS, and EDS. Their catalytic performances are evaluated by hydrogenation of olefins. Pd@CPP-Y exhibits higher catalytic activity and recyclability than Pd@CPP-C. Hot filtration and the three-phase test indicate that hydrogenation functions in a heterogeneous pathway.

A new strategy for in situ generation of well-dispersed palladium nanoparticles (NPs) immobilized in imidazolium-based organic ionic polymers was presented. Without extra addition of palladium species, the as-synthesized ionic polymers showed excellent catalytic activity and good reusability in the hydrogenation of nitroarenes.