In this work, a series of novel multistimulus-responsive lanthanide coordination polymers {[LnL(H2O)4]Cl3·3H2O} n (Ln = Dy, Tb, Eu) constructed using a dicarboxylic acid viologen derivative L (L = N,N′-4,4′-bipyridiniodipropionate) and LnCl3·6H2O were prepared. All materials showed positive responses to UV light, and the photochromic phenomena accompanied by significant photoquenching of photoluminescence could be observed through a photoelectron transfer mechanism. Strikingly, the Dy analogue displayed photomagnetic behavior, as well as responded positively to small molecules of inorganic ammonia/organic amines. Furthermore, the good photoresponsive and ammonia/amine vapor-responsive properties of the Dy-based material were further fulfilled in dual-function papers involving erasable inkless printing and visual amine detection applications. This work aims to advance the development of multistimulus-responsive multifunctional materials incorporating viologen derivates and versatile lanthanide ions and further enriches the research in this field.

Electromagnetic waves at the X band (8.2–12.4 GHz) play significant roles in military applications such as radar, satellite, and wireless communication. However, within this band range, the developed performance of electromagnetic absorption (EMA) is still unsatisfied, and it is hard to settle the corresponding problems on radar stealth and electromagnetic pollution. Herein, we demonstrate a state-of-the-art EMA property of −82.6 dB at 8.24 GHz with 2.57 mm thickness and 30 wt % paraffin filling ratio. For this purpose, an optimal Co@NCS/Ti3C2T x composite is prepared by an electrostatic self-assembly approach through compelling Co-loading of nitrogen-doped carbon sheets (Co@NCS) derived from the pyrolysis of ZIF-67 (CoZn) with 2D Ti3C2T x MXene nanosheets. Experimental results show that the highly efficient EMA performance of this Co@NCS/Ti3C2T x composite originates from the large surface area for multiple reflection and electromagnetic wave scattering, from abundant defects sites for dipole and interfacial polarization, and from the optimizing impedance matching by the combination of Co magnetic nanoparticles and conductive NCS/Ti3C2T x composite. These results confirm that the as-fabricated composites possess scientific and practical values for EMA applications at the X band, paving the way for developing highly performant electromagnetic absorbers toward specific microwave bands.