A spongy nickel-organic photocatalyst with nearly 100% selective CO2 to CO conversion.

Porous-carbon-based nanocomposites are gaining tremendous interest because of good compatibility, lightweight, and strong electromagnetic wave absorption. However, it is still a great challenge to design and synthesize porous-carbon-based composites with strong absorption capability and broad frequency bandwidth. Herein, a facile and effective method was developed to synthesize Co magnetic nanoparticles/metal organic framework (MOF) (Co NPs/ZIF-67) nanocomposites. Co NPs/porous C composites were subsequently obtained by annealing Co NPs/ZIF-67 nanocomposites at different temperatures under an inert atmosphere. The carbonized nanocomposites showed highly efficient electromagnetic wave absorption capability. Specifically, the optimal composite (i.e., Co/C-700) possessed a maximum reflection loss (RL) value of -30.31 dB at 11.03 GHz with an effective absorption bandwidth (RL ≤ -10 dB) of 4.93 GHz. The electromagnetic parameters and the absorption performance of the composites are readily tunable by adjusting the carbonization temperature and the concentration of Co NPs in the composites. Because of the combination of good impedance matching, dual-loss mechanism, and the synergistic effect between Co NPs and porous carbon composites, these Co NPs/MOF-derived composites are attractive candidates for electromagnetic wave absorbers.

In this work, cobalt/polypyrrole (Co/PPy) nanocomposites were prepared via an in situ oxidation polymerization of pyrrole in an aqueous dispersion of Co nanoparticles (NPs). The Co/PPy nanocomposites showed good electromagnetic properties because of the coexistence of magnetic loss and dielectric loss to electromagnetic waves. The electromagnetic wave absorbing bandwidth (reflection loss < -10 dB) for Co/PPy (30 wt% in a paraffin matrix) was located at 11.7-16.47 GHz with a thickness of 2 mm, and with a maximum reflection loss (around -33 dB) at 13.6 GHz. More interestingly, the electromagnetic wave absorbing properties of the nanocomposites can be easily controlled by tuning the ratio of the two components in the composites. This improved electromagnetic wave absorption may be attributed to the excellent electromagnetic match at the corresponding resonance peaks for dielectric and magnetic loss. These magnetic nanoparticles/conducting polymer nanocomposites are great potential candidates for use as electromagnetic wave absorbents due to their excellent properties such as wide absorbing frequency, strong absorption, good compatibility, low density and controllable absorbing properties.