Since their discovery in 2011, MXenes (abbreviation for transition metal carbides, nitrides, and carbonitrides) have emerged as a rising star in the family of 2D materials owing to their unique properties. Although the primary research interest is still focused on pristine MXenes and their composites, much attention has in recent years been paid also to MXenes with diverse compositions. To this end, this work offers a comprehensive overview of the progress on compositional engineering of MXenes in terms of doping and substituting from theoretical predictions to experimental investigations. Synthesis and properties are briefly introduced for pristine MXenes and then reviewed for hetero‐MXenes. Theoretical calculations regarding the doping/substituting at M, X, and T sites in MXenes and the role of vacancies are summarized. After discussing the synthesis of hetero‐MXenes with metal/nonmetal (N, S, P) elements by in situ and ex situ strategies, the focus turns to their emerging applications in various fields such as energy storage, electrocatalysts, and sensors. Finally, challenges and prospects of hetero‐MXenes are addressed. It is anticipated that this review will be beneficial to bridge the gap between predictions and experiments as well as to guide the future design of hetero‐MXenes with high performance.

As one of the rising 2D materials, niobium‐carbide (Nb2C, well‐known as a member of MXene family) has attracted considerable attention owing to its unique physical and chemical properties. In this work, few‐layer Nb2C nanosheets (NSs) with large (≈255 nm) and small (≈48 nm) lateral dimensions are obtained via a combination of selective etching and liquid cascade centrifugation. Their relaxation time and photophysics process are systematically investigated by transient absorption spectroscopy, and the size effect is demonstrated by phonon‐bottleneck mechanism. Ultrafast fast relaxation time (37.43 fs) and slow relaxation time (0.5733 ps) are observed due to the symmetric structure and metallicity of Nb2C NSs. The nonlinear optical properties of Nb2C NSs are studied by Z‐scan technique, and both saturable absorption and reverse‐saturable absorption are observed. According to first principle calculations, these phenomena can be attributed to the special band structure of Nb2C near the Fermi level, where two‐photon absorption or multiphoton absorption may occur under the irradiation of long wavelength light. These intriguing results suggest that few‐layer Nb2C NSs can be used as building blocks for broadband ultrafast photonics and optoelectronic devices and also hold the potential for breakthrough developments in these fields.

Optoelectronic science and 2D nanomaterial technologies are currently at the forefront of multidisciplinary research and have numerous applications in electronics and photonics. The unique energy and optically induced interfacial electron transfer in these nanomaterials, enabled by their relative band alignment characteristics, can provide important therapeutic modalities for healthcare. Given that nano‐heterostructures can facilitate photoinduced electron–hole separation and enhance generation of reactive oxygen species (ROS), 2D nano‐heterostructure‐based photosensitizers can provide a major advancement in photodynamic therapy (PDT), to overcome the current limitations in hypoxic tumor microenvironments. Herein, a bismuthene/bismuth oxide (Bi/BiOx)‐based lateral nano‐heterostructure synthesized using a regioselective oxidation process is introduced, which, upon irradiation at 660 nm, effectively generates 1O2 under normoxia but produces cytotoxic •OH and H2 under hypoxia, which synergistically enhances PDT. Furthermore, this Bi/BiOx nano‐heterostructure is biocompatible and biodegradable, and, with the surface molecular engineering used here, it improves tumor tissue penetration and increases cellular uptake during in vitro and in vivo experiments, yielding excellent oxygen‐independent tumor ablation with 660 nm irradiation, when compared with traditional PDT agents.

A highly diastereoselective and practical biomimetic total synthesis of (±)-basiliolide B has been achieved through the study of the two proposed biosynthetic pathways (O-methylation and O-acylation) for the unprecedented 7-methoxy-4,5-dihydro-3H-oxepin-2-one (C ring). The synthesis featured a cyclopropanation/ring opening strategy for establishing the stereogenic centers at C8 and C9, a biomimetic 2-pyrone Diels-Alder cycloaddition for the synthesis of the ABD ring system, and finally a highly efficient biomimetic intramolecular O-acylation for the C ring formation. This result provides an important perspective on the biosynthetic origin of the unprecedented 7-membered acyl ketene acetal moiety of the C ring.

By breaking the restriction of mirrors, random lasers from a disordered medium have found unique applications spanning from displays to spectroscopy to biomedical treatments to light fidelity. Gain media in two dimensions with distinct physical and chemical properties may lead to the next generation of random lasers. Graphdiyne (GDY), a two-dimensional graphene allotrope with intrigued carbon hybridization, atomic lattice, and optoelectronic properties, has attracted increasing attention recently. Herein, the photoemission characteristics and photocarrier dynamics in GDY are systematically studied, and multicolor random lasers have been unprecedently realized using GDY nanosheets as the gain. Considering the well biocompatibility of GDY, these results may look ahead to a plethora of potential applications in the nanotechnology platform based on GDY.

Successful treatment of Parkinson's disease (PD) is impeded by limited permeability of the blood brain barrier (BBB) which causes unsatisfactory drug accumulation in the central nervous system (CNS).In the present study, a novel 2D graphdiyne (GDY)-based nanoplatform is utilized for the delivery of minocycline (MN), one drug candidate for PD treatment. These GDY nanosheets are prepared by sonication and exhibit excellent photothermal (PT) conversion ability (≈32%) without obvious toxicity in vitro. MN can be loaded onto GDY by -stacking (≈90%) and near infrared (NIR) irradiation is able to trigger the release of more than 30% of the payload. The BBB permeability of GDY is confirmed in both cellular and animal models. The behavioral defects of PD mice can be corrected after the PT and chemical synergistic treatment performed by GDY, with the dopaminergic neuron counting restored to normal level. Nanosheets-mediated PT treatment exhibits comparable therapeutic effects to that of L-DOPA, a commercialized PD drug. No obvious damage to major organs or circulation system is detected and physiological parameters remain stable during the behavioral study. This GDY-based delivery system can serve as a promising platform for loading chemical drugs targeting neurodegenerative disorders.

A novel triptycene-based hyper-crosslinked porous polymer was developed for the highly efficient entrapment of organic dyes from aqueous solution.

A concise formal synthesis of (+)-phomactin A has been achieved. The key features of this synthetic strategy involve a one-pot Prins/Conia-ene cyclization protocol for the construction of the highly functionalized 1-oxadeclin core (AB ring) and a late-stage direct γ-hydroxylation of enone for the installation of the C ring.