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Recently, Mn(II)-based T1-weighted magnetic resonance imaging (MRI) contrast agents (CAs) have been explored widely for cancer diagnosis. However, the “always-on” properties and poor excretability of the conventional Mn(II)-based CAs leads to high background signals and unsatisfactory clearance from the body. Here, we report an “in situthree-dimensional to two-dimensional (3D-to-2D) transformation” method to prepare novel excretable 2D manganese-based layered silicates (Mn-LSNs) with extremely high signal-to-noise for tumor-specific MR imaging for the first time. Our observations combined with density functional theory (DFT) calculations reveal that 3D metal (Mn, Fe, Co) oxide nanoparticles are initially formed from the molecular precursor solution and then in situtransform into 2D metal (Mn, Fe, Co)-based layered silicates triggered by the addition of tetraethyl orthosilicate, which provides a time-saving and versatile way to prepare novel 2D silicate nanomaterials. The unique ion-exchangeable capacity and high host layer charge density endow Mn-LSNs with an “ON/OFF” pH/GSH stimuli-activatable T1relaxivity with superb high signal-to-noise (640-, 1200-fold for slightly acidic and reductive changes, respectively). Further in vivoMR imaging reveals that Mn-LSNs exhibit a continuously rapid T1-MRI signal enhancement in tumor tissue and no visible signal enhancement in normal tissue, indicating an excellent tumor-specific imaging. In addition, Mn-LSNs exhibit a rapid excretion from the mouse body in 24 h and invisible organ toxicity, which could help to solve the critical intractable degradation issue of conventional inorganic CAs. Moreover, the tumor microenvironment (pH/GSH/H2O2) specific degradability of Mn-LSNs could help to improve the penetration depth of particles into the tumor parenchyma. Developing this novel Mn-LSNs contrast agent, together with the already demonstrated capacity of layered silicates for drug and gene delivery, provides opportunities for future cancer theranostics.

Though many efforts have been devoted to the adsorptive removal of hazardous materials of organophosphorus pesticides (OPs), it is still highly desirable to develop novel adsorbents with high adsorption capacities. In the current work, the removal of two representative OPs, glyphosate (GP) and glufosinate (GF), was investigated by the exceptionally stable Zr-based MOFs of UiO-67. The abundant Zr–OH groups, resulting from the missing-linker induced terminal hydroxyl groups and the inherent bridging ones in Zr–O clusters of UiO-67 particles, served as natural anchorages for efficient GP and GF capture in relation with their high affinity toward phosphoric groups in OPs. The correlation between the most significant parameters such as contact time, OPs concentration, adsorbent dose, pH, as well as ionic strength with the adsorption capacities was optimized, and the effects of these parameters on the removal efficiency of GP and GF from the polluted aqueous solution were investigated. The adsorption of GP on UiO-67 was faster than that of GF, and a pseudo-second-order rate equation effectively described the uptake kinetics. The Langmuir model exhibited a better fit to adsorption isotherm than the Freundlich model. Thanks to the strong affinity and adequate pore size, the adsorption capacities in UiO-67 approached as high as 3.18 mmol (537 mg) g–1for GP and 1.98 mmol (360 mg) g–1for GF, which were much higher than those of many other reported adsorbents. The excellent adsorption characteristics of the current adsorbents toward OPs were preserved in a wide pH window and high concentration of the background electrolytes. These prefigured the promising potentials of UiO-67 as novel adsorbent for the efficient removal of OPs from aqueous solution.