A Two-Dimensional Tb-MOF Nanosheet for Simultaneous Detection and Adsorption of 2,6-Dichloro-4-nitroaniline in Water

The extensive use of pesticides like 2,6-dichloro-4-nitroaniline (DCN) poses serious risks to aquatic environments and human health, necessitating effective tools for both monitoring and remediation. Here, a new hydrostable, two-dimensional, terbium-based metal–organic framework, {[Tb2(HL)2(NO2)]·3H2O·0.5DMF}n (Tb-LMOF), was developed using a novel piperazine-bridged multicarboxylate ligand (H4L). The layered structure of Tb-LMOF is readily exfoliated into ultrathin nanosheets (Tb-LMOF-NS) via ultrasonication, exploiting the weak van der Waals interlayer interactions. The resulting Tb-LMOF-NS integrates two crucial functions: it serves as an ultrasensitive luminescent sensor for DCN in water, achieving a detection limit of 33.34 nM with a fast response time of 20 s, and as an efficient adsorbent, exhibiting a high capacity of 184.1 mg·g–1 with rapid kinetics. Mechanistic studies, combining spectroscopy and DFT calculations, reveal that the sensing originates from a synergistic inner-filter effect, competitive absorption, and photoinduced electron transfer, while the adsorption is governed by specific hydrogen-bonding interactions. Furthermore, a portable Tb-LMOF-NS@PMMA composite film enables visual, on-site detection of DCN residues on vegetable surfaces with smartphone-assisted quantification. This work presents a compelling integrated platform that bridges ultrasensitive detection and efficient removal of DCN, highlighting the untapped potential of 2D Ln-MOF nanosheets for environmental applications.