Advancements in porous framework materials for chemiresistive hydrogen sensing: Exploring MOFs and COFs

Abstract

Hydrogen is a zero-emissive fuel and has immense potential to replace carbon-emitting fuels in the future. The need for the development of efficient H2 sensors are essential for preventing hazardous situations and facilitating its widespread usage. Chemiresistors are popular gas sensors owing to their attractive properties such as fast response, miniaturization, simple integration with electronics and low cost. Traditionally, semiconducting metal oxides (SMOs) and Pd-based materials have been widely investigated for chemiresistive H2 sensing applications. However, issues such as limited selectivity and poor reliability still hinder their use in real-time applications. Recent advancements have explored Metal-Organic Frameworks (MOFs) and Covalent-Organic Frameworks (COFs), offering new perspectives and potential applications in this field. MOFs and COFs belong to crystalline frameworks (CFs), are highly porous, designable materials with tunable pore surfaces with featuring sites for H2 interaction. They exhibit good selectivity with quick response/recovery times towards H2 at relatively low temperatures compared to SMOs. Further, they endeavor additional advantage of sensing H2 in the absence of oxygen and even at high concentrations of H2. In this perspective article, we summarize the recent advancements and challenges in the development of H2 sensors employing MOFs, COFs, and their hybrid composites as sensing elements. Additionally, we have discussed our perspective on hybridizing MOFs/COFs with SMOs and other nanomaterials for the future development of advanced H2 sensors.