The in situ synthesis of mesoporous nanotubes from natural minerals remains a great challenge. Herein, we report the successful synthesis of mesoporous silica nanotubes (MNTs) with a varying inner-shell thickness and a preserved clay outer shell from natural-halloysite nanotubes (HNTs). After the enlargement of the lumen diameter of the tubular aluminosilicate clay by acid leaching, uniform mesopores were introduced by a modified pseudomorphic transformation approach, while the clay outer shell was well-preserved. Using density functional theory calculations, the atomic structure evolution and the energetics during Al leaching and Si–OH condensation were studied in detail. After the leaching of Al ions from the HNTs, local structural changes from Al(Oh) to Al(V) at a medium leaching level and to Al(Td) at a high leaching level were confirmed. The calculated hydroxylation energy of two kinds of silica components in the acid-leached HNTs (the distorted two-dimensional silica source in the inner shell and the intact aluminosilicate structure in the outer shell) was 0.5 eV lower or 1.0 eV higher than that of bulk silica, which clarifies the different behavior of the silica components in the hydrothermal process. The successful synthesis of reactive MNTs from HNTs introduces a new strategy for the synthesis of mesoporous nanocontainers with a special morphology using natural minerals. In particular, MNT samples with numerous reactive Al(V) species and a specific surface area up to 583 m²/g (increased by a factor of 10) are promising drug-loading nanocontainers and nanoreactors.

Natural two-dimensional (2D) kaolinite nanoclay has been incorporated into an emerging drug delivery system. The basal spacing of the kaolinite nanoclay was expanded from 0.72 to 4.16 nm through the intercalation of various organic guest species of different chain lengths, which can increase the efficiency in drug delivery and reduce the toxicity of doxorubicin (DOX). Original kaolinite (Kaolin) and the Kaolin intercalation compounds exhibited a high level of biocompatibility and very low toxicity towards cells of pancreatic cancer, gastric cancer, prostate cancer, breast cancer, colorectal cancer, esophageal cancer, and differentiated thyroid cancer. However, lung cancer and hepatocellular cancer cells need more strict compositional, structural, and morphological modulations for drug delivery carriers. DOX-Kaolin and the DOX-Kaolin intercalation compounds showed dramatically faster drug release in moderately acidic solution than in neutral condition, and exhibited enhanced therapeutic effects against ten model cancer cell cultures in a dose-dependent manner. The use of 2D nanoclay materials for a novel drug delivery system could feasibly pave a way towards high-performance nanotherapeutics, with superior antitumor efficacy and significantly reduced side effects.

Emerging hierarchical MoS₂/pillared-montmorillonite (MoS₂/PMMT) hybrid nanosheets were successfully prepared through facile in-situ hydrothermal synthesis of MoS₂ within the interlayer of cetyltrimethylammonium bromide PMMT, and their catalytic performance was evaluated by the reduction reaction of 4-nitrophenol (4-NP) using NaBH₄ as a reductant. Microstructure and morphology characterization indicated that MoS₂/PMMT exhibited hybrid-stacked layered structures with an interlayer spacing of 1.29 nm, and the MoS₂ nanosheets were intercalated within the montmorillonite (MMT) layers, with most of the edges exposed to the outside. The catalytic activity and stability of MoS₂/PMMT were both enhanced by the MMT. With the MoS₂/PMMT as the catalyst, the apparent reaction rate constant of the 4-NP reduction was 0.723 min^-1 and was maintained at ~0.679 min^-1 after five reaction cycles. The structural evolution of MoS₂/PMMT and the possible catalysis mechanism for the reduction reaction of 4-NP were investigated. The as-prepared MoS₂/PMMT hybrid nanosheets are promising candidates for catalytic application in the water-treatment and biomedical fields. The strategy developed in this study can provide insights for designing hybrid nanosheets with diverse heterogeneous two-dimensional (2D) nanomaterials.