Abstract Gas sensors are valuable tools for human applications, and extensive research has been conducted in this field. However, practical implementation has yet to be fully realized. In response, efforts have been made to explore metal-organic frameworks (MOFs), a novel class of porous materials, as potential solutions. MOFs exhibit exceptional porosity and highly tunable chemical compositions and structures, giving rise to a wide range of unique physical and chemical properties. Significant progress has been achieved in developing MOF-based gas sensors, improving sensing performance for various gases. This review aims to provide a comprehensive understanding of MOF-based gas sensors, even for readers unfamiliar with MOFs and gas sensors. It covers the working principles of these sensors, fundamental concepts of MOFs, strategies for tuning MOF properties, fabrication techniques for MOF films, and recent studies on MOF and MOF-derivative gas sensors. Finally, current challenges, overlooked aspects, and future directions for fully exploiting the potential of MOFs in gas sensor development are discussed.

• A scalable catalyst coating method was developed using FeNi-MOF particles and an FCNT hydrogel. • Uniform dispersion of MOF on FCNT scaffolds increased active site exposure and created a well-connected conductive structure. • During OER, the MOF transformed into a hybrid structure of metal hydroxides and organic materials, with FeNiOOH as the actual active site. • The catalyst demonstrated low overpotentials of 263 mV at 10 mA/cm 2 and 355 mV at 100 mA/cm 2 in half-cell tests. • In AEMWE, the system achieved 1.8 V at 1 A/cm 2 , outperforming IrO x /Nafion_CC by 0.69 V at a loading of 0.2 mg/cm 2 . We developed a scalable binder-free composite electrode layer fabrication method by integrating Fe-Ni-based MIL-101 MOF catalysts for the oxygen evolution reaction (OER) with carbon nanotube (CNT) scaffolds. This synergy significantly enhanced active site exposure, as the MOF uniformly dispersed across the CNT surface, forming a 3D electroconductive structure. In particular, the MOFs are further transformed into the hybrid structure of metal hydroxide and organic compounds during OER conditions, leading to an enhanced and stable catalytic layer. The resulting electrode exhibited improved catalytic performance, with overpotentials of 263 mV at 10 mA/cm 2 and 355 mV at 100 mA/cm 2 in half-cell tests. In an alkaline exchange membrane water electrolyzer (AEMWE), the electrode achieved a voltage of 1.8 V at 1 A/cm 2 , with an overpotential 0.69 V lower than that of the conventional IrO x /Nafion_CC electrode at a loading of 0.2 mg cm −2 . Our method effectively overcomes the scalability challenges associated with traditional catalyst growth strategies and demonstrates that MOF materials can function as electrocatalysts without further treatment.

Binder-free supercapacitors are effective in achieving rapid charging/discharging capabilities, high power/energy density, and potentially reduced manufacturing costs. In this study, hierarchical carbon nanoplates (HCN) fabricated through the carbonization of high aspect ratio, polycrystalline metal-organic framework nanoplates. These HCN structures are then hybridized with functionalized carbon nanotube (FCNT) scaffolds and applied as electrodes using a scalable shear-coating method, eliminating the need for binders. The synergistic effects of these components result in the capacitance of 206 F/g at 0.8 A/g and 148.8 F/g at 8 A/g with a retention of 72 % in half-cell setups, and a full symmetric cell capacitance of 126 F/g at 4 A/g and 76 F/g at 40 A/g with a retention rate of 61%. The power and energy densities of the full cell were measured to be 3880 W/Kg and 16.2 Wh/Kg, surpassing the upper bound for electrochemical capacitors. The high rate capability and capacitance are attributed to the well-designed architecture of the electrodes and the benefits of the carbon components. Specifically, the high aspect ratio of the HCN with the hierarchical pore structure enhances the active surface area and charge transport properties. Additionally, the increased intermolecular interactions within the FCNT phase create entangled scaffolds, imparting both conductive pathways and mechanical stability. The binder-free nature of the electrodes, complemented by the presence of HCN spacers in the FCNT matrix, expands pores and promotes the transfer of ion species. Importantly, the viscoelastic properties of the HCN/FCNT slurry enable electrode fabrication in large areas by a scalable coating method.