This review summarizes the latest advances in design principles based on metastable metal chalcogenide nanomaterials (MCNs), together with corresponding soft chemical transformation rules to prepare or modify MCNs with novel or enhanced properties.

Metallic-phase transition-metal dichalcogenides (TMDCs) exhibit unusual physicochemical properties compared with their semiconducting counterparts. However, they are thermodynamically unstable to access and it is even more challenging to construct their metastable-phase heterostructures. Herein, we demonstrate a general solution protocol for phase-controlled synthesis of distorted octahedral 1T WS 2 -based (1T structure denotes an octahedral coordination for W atom) multidimensional hybrid nanostructures from two-dimensional (2D), one-dimensional (1D), and zero-dimensional (0D) templates. This is realized by tuning the reactivity of tungsten precursor and the interaction between crystal surface and ligands. As a conceptual study on crystal phase-and dimensionality-dependent applications, we find that the three-dimensional (3D) hierarchical architectures achieved, comprising 1T WS 2 and 2D Ni 3 S 4 , are very active and stable for catalyzing hydrogen evolution. Our results open up a new way to rationally design phase-controlled nanostructures with increased complexity and more elaborate functionalities.

Soft matter catalyst system allowing controllable manipulation of the organized nanostructure and surface property holds the potential for renewable energy. Here we demonstrate the construction of a continuously regenerative hydrogel photocatalyst that confines the metal-thiolate coordination induced nanocavity into robust micro-sized spongy network for water splitting. Thanks to low vaporization enthalpy and fast proton mobility of water molecules confining in nanocavities, the composite delivers outstanding photocatalytic H 2 production (TOF of 4568 H 2 h À 1 ), nearly 4.5 times higher than that on the catalyst without confinements. Incorporating with conductive polymers, the TOF is substantially improved to 7819 H 2 h À 1 . Impressively, continuous regeneration is for the first time achieved with H 2 production retention improved from 24 % to 72 % by regulating optically-active catalyst surfaces. This optical regeneration method provides new avenues for sustainable solar energy conversion.