Two‐dimensional (2D) materials have attracted increasing attention for their outstanding structural and electrical properties. However, for mass‐production of field effect transistors (FETs) and potential applications in integrated circuits, large‐area and uniform 2D thin films with high mobility, large on‐off ratio, and desired polarity are needed to synthesize firstly. Here, a transfer‐free growth method for platinum diselenide (PtSe2) films has been developed. The PtSe2 films have been synthesized with various thicknesses in centimeter‐sized scale. Typical FET made from a few layer PtSe2 show p‐type unipolar, with a high field‐effect hole mobility of 6.2 cm2 V−1 s−1 and an on‐off ratio of 5 × 103. The versatile semimetal‐unipolar‐ambipolar transition in synthesized PtSe2 films is also firstly observed as the thickness thinning. This work realizes the large‐scale preparation of PtSe2 with prominent electrical properties and provides a new strategy for polarity's modulation.

With tunable pore size and rich active metal centers, metal–organic frameworks (MOFs) have been regarded as the one of the promising materials for catalysis. Prospectively, employing MOFs in electrochemistry would notably broaden the scope of electrocatalysis. However, this application is largely hindered by MOFs’ conventionally poor electrical conductivity. Integrating MOFs without compromising their crystalline superiority holds a grand challenge to unveil their pristine electrocatalytic properties. In this work, we introduce an epitaxial growth strategy to accomplish the efficient integration of the insulating MOFs into electrochemistry. Particularly, with pristine-graphene-templated growth, the two-dimensional (2D) single-crystal MOF possesses a large lateral size of ∼23 μm and high aspect ratio up to ∼1500 and exhibits a significant electrochemical enhancement, with a charge transfer resistance of ∼200 ohm and a 30 mA cm–2 current density at only 0.53 V versus a reversible hydrogen electrode. The epitaxial strategy could be further applied to other 2D substrates, such as MoS2. This MOF/graphene 2D architecture sheds light on integrating insulating MOFs into electrochemical applications.

Electronics allowing for visible light to pass through are attractive, where a key challenge is to make the core functional units transparent. Here, it is shown that transparent electronics can be constructed by epitaxial growth of metal–organic frameworks (MOFs) on single‐layer graphene (SLG) to give a desirable transparency of 95.7% to 550 nm visible light and an electrical conductivity of 4.0 × 104 S m−1. Through lattice and symmetry match, collective alignment of MOF pores and dense packing of MOFs vertically on SLG are achieved, as directly visualized by electron microscopy. These MOF‐on‐SLG constructs are capable of room‐temperature recognition of gas molecules at the ppb level with a linear range from 10 to 108 ppb, providing real‐time gas monitoring function in transparent electronics. The corresponding devices can be fabricated on flexible substrates with large size, 3 × 5 cm, and afford continuous folding for more than 200 times without losing conductivity or transparency.

Monolayer hexagonal boron nitride (h-BN) possesses a wide bandgap of ~6 eV. Trimming down the bandgap is technically attractive, yet poses remarkable challenges in chemistry. One strategy is to topological reform the h-BN’s hexagonal structure, which involves defects or grain boundaries (GBs) engineering in the basal plane. The other way is to invite foreign atoms, such as carbon, to forge bizarre hybrid structures like hetero-junctions or semiconducting h-BNC materials. Here we successfully developed a general chemical method to synthesize these different h-BN derivatives, showcasing how the chemical structure can be manipulated with or without a graphene precursor, and the bandgap be tuned to ~2 eV, only one third of the pristine one’s.

Electrocatalytic reduction of N2 to NH3 under an ambient atmosphere is highly desirable and extremely critical for energy-efficient nitrogen utilization. Inspired by the natural MoFe protein-based enzyme, the nitrogenase, we exploited this electrochemical process with a unique two-dimensional catalyst, namely, molybdenum carbide (Mo2C). The catalyst is synthesized through a chemical vapor deposition method, with a highly orientated (200) facet of the α-Mo2C phase. A remarkable Faradaic efficiency as high as 40.2% has been achieved on the (200) faceted α-Mo2C during the nitrogen reduction reaction (NRR). Density functional theory calculations confirm that rate-determining steps *NNH2 → *NNH3 and *NH → *NH2 experience a low energy barrier on the (200) surface following the proton–electron coupled, distal associated mechanism. To protect Mo from leaching during the NRR process, we also grew layers of graphene on top of Mo2C, forming a chemically enduring two-dimensional heterostructured electrode.