Catalysis with single-atom catalysts (SACs) exhibits outstanding reactivity and selectivity. However, fabrication of supports for the single atoms with structural versatility remains a challenge to be overcome, for further steps toward catalytic activity augmentation. Here, we demonstrate an effective synthetic approach for a Pt SAC stabilized on a controllable one-dimensional (1D) metal oxide nano-heterostructure support, by trapping the single atoms at heterojunctions of a carbon nitride/SnO2 heterostructure. With the ultrahigh specific surface area (54.29 m2 g–1) of the nanostructure, we obtained maximized catalytic active sites, as well as further catalytic enhancement achieved with the heterojunction between carbon nitride and SnO2. X-ray absorption fine structure analysis and HAADF-STEM analysis reveal a homogeneous atomic dispersion of Pt species between carbon nitride and SnO2 nanograins. This Pt SAC system with the 1D nano-heterostructure support exhibits high sensitivity and selectivity toward detection of formaldehyde gas among state-of-the-art gas sensors. Further ex situ TEM analysis confirms excellent thermal stability and sinter resistance of the heterojunction-immobilized Pt single atoms.

Conductive metal-organic framework (C-MOF) thin-films have a wide variety of potential applications in the field of electronics, sensors, and energy devices. The immobilization of various functional species within the pores of C-MOFs can further improve the performance and extend the potential applications of C-MOFs thin films. However, developing facile and scalable synthesis of high quality ultra-thin C-MOFs while simultaneously immobilizing functional species within the MOF pores remains challenging. Here, we develop microfluidic channel-embedded solution-shearing (MiCS) for ultra-fast (≤5 mm/s) and large-area synthesis of high quality nanocatalyst-embedded C-MOF thin films with thickness controllability down to tens of nanometers. The MiCS method synthesizes nanoscopic catalyst-embedded C-MOF particles within the microfluidic channels, and simultaneously grows catalyst-embedded C-MOF thin-film uniformly over a large area using solution shearing. The thin film displays high nitrogen dioxide (NO2) sensing properties at room temperature in air amongst two-dimensional materials, owing to the high surface area and porosity of the ultra-thin C-MOFs, and the catalytic activity of the nanoscopic catalysts embedded in the C-MOFs. Therefore, our method, i.e. MiCS, can provide an efficient way to fabricate highly active and conductive porous materials for various applications.

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Conductive metal–organic frameworks (cMOFs) are emerging materials for various applications due to their high surface area, high porosity, and electrical conductivity. However, it is still challenging to develop cMOFs having high surface reactivity and durability. Here, highly active and stable cMOF are presented via the confinement of bimetallic nanoparticles (BNPs) in the pores of a 2D cMOF, where the confinement is guided by dipolar‐interaction‐induced site‐specific nucleation. Heterogeneous metal precursors are bound to the pores of 2D cMOFs by dipolar interactions, and the subsequent reduction produces ultrasmall (≈1.54 nm) and well‐dispersed PtRu NPs confined in the pores of the cMOF. PtRu‐NP‐decorated cMOFs exhibit significantly enhanced chemiresistive NO2 sensing performances, owing to the bimetallic synergies of PtRu NPs and the high surface area and porosity of cMOF. The approach paves the way for the synthesis of highly active and conductive porous materials via bimetallic and/or multimetallic NP loading.

Iminosemiquinone‐linker‐based conductive metal–organic frameworks (c‐MOFs) have attracted much attention as next‐generation electronic materials due to their high electrical conductivity combined with high porosity. However, the utility of such c‐MOFs in high‐performance devices has been limited to date by the lack of high‐quality MOF thin‐film processing. Herein, a technique known as the microfluidic‐assisted solution shearing combined with post‐synthetic rapid crystallization (MASS‐PRC) process is introduced to generate a high‐quality, flexible, and transparent thin‐film of Ni3(hexaiminotriphenylene)2 (Ni3(HITP)2) uniformly over a large‐area in a high‐throughput manner with thickness controllability down to tens of nanometers. The MASS‐PRC process utilizes: 1) a micromixer‐embedded blade to simultaneously mix and continuously supply the metal–ligand solution toward the drying front during solution shearing to generate an amorphous thin‐film, followed by: 2) immersion in amine solution for rapid directional crystal growth. The as‐synthesized c‐MOF film has transparency of up to 88.8% and conductivity as high as 37.1 S cm−1. The high uniformity in conductivity is confirmed over a 3500 mm2 area with an arithmetic mean roughness (Ra) of 4.78 nm. The flexible thin‐film demonstrates the highest level of transparency for Ni3(HITP)2 and the highest hydrogen sulfide (H2S) sensing performance (2,085% at 5 ppm) among c‐MOFs‐based H2S sensors, enabling wearable gas‐sensing applications.