High-performance broadband microwave absorbers are greatly required to cope with the increasingly serious microwave radiation pollution. Integration of dielectric and magnetic components is a promising strategy to achieve desirable microwave absorption performance. Herein, we demonstrated a facile and efficient approach to fabricate two-dimensional cobalt@carbon (Co@C) hybrids by solvothermal synthesis of cobalt–metal–organic framework (Co-MOF) nanosheets and subsequent thermal pyrolysis for efficient microwave absorption application. The resultant nanolayered Co@C hybrids inherit the two-dimensional architecture of the Co-MOF nanosheets. During the thermal pyrolysis of Co-MOF, its organic component is carbonized to amorphous carbon while its cobalt ions are carbothermally reduced to cobalt nanoparticles, thus in situ integrating the magnetic metal nanocrystal with the dielectric carbon. Consequently, a wide effective absorption bandwidth of 5.44 GHz at a small thickness of 1.76 mm and a minimum reflection loss value of −49.76 dB are achieved for the wax composite with 30 wt % of Co@C hybrid pyrolyzed at 800 °C. The outstanding microwave absorption performances are attributed to the synergistic effects of the Co@C hybrid nanosheets and their large shape anisotropy, which facilitates the strong dielectric loss and good impedance matching, thus promising the nanolayered Co@C hybrid as a lightweight and high-performance microwave absorber.

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Polylactide [PLA, two enantiomers: poly­(l-lactide) (PLLA) and poly­(d-lactide) (PDLA)] has been widely applied as biomaterials because of its biocompatibility, biodegradability, and good mechanical capacity. However, the chirality of PLA materials has not been intensively explored yet. In the present study, chiral porous poly­(high internal-phase emulsion)­s (polyHIPEs) derived from enantiopure PLAs were successfully prepared via a HIPE template method. The resulting polyHIPEs show optical activity. More interestingly, the polyHIPEs demonstrate enantioselective release capacity, using cinchona alkaloid and naproxen as the model chiral drugs. Notably, PLLA-based polyHIPE shows enantioselectivity in both the drug-loading step and drug-releasing step, while PDLA-based polyHIPE fails. The interesting finding is essentially different from other chiral polymer materials reported earlier. The cytotoxicity test demonstrates that all the three types of polyHIPEs, PLLA-, PDLA-, and PDLLA-based polyHIPE show biocompatibility; however, their different chirality exerts varying effects on cell growth. Accordingly, special attention should be devoted to the chirality of PLA when used as biomaterials.

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