Metal–Organic Frameworks–Based Surface–Enhanced Raman Scattering Substrates for Gas Sensing

Gas sensing holds great significance in environment monitoring, real–time security alerts and clinical diagnosis, which require sensing technology to distinguish various target molecules with extreme sensitivity and selectivity. Surface–enhanced Raman spectroscopy (SERS) has great potential in gas sensing for its single molecule sensitivity and fingerprint specificity. However, different from molecule sensing in solutions, SERS detection of gas often suffers from low sensitivity as gas molecules usually display a low Raman cross–section and poor affinity on traditional noble metal nanoparticle (NMNP)–based substrates. Therefore, much effort has been made to solve these problems. Fortunately, the appearance of metal–organic frameworks (MOFs) has shed new light on this direction. Due to the unique functional characteristics of MOFs, such as controllable pore size/shape, structural diversity and large specific surface area, SERS substrates based on MOFs can achieve high sensitivity, excellent selectivity and good stability. Although several reviews on MOF–based SERS substrates have been reported, few focus on gas sensing, which is a great challenge. Here, we mainly review the latest research progress on SERS substrates based on different MOFs. Sensitive and active SERS substrates can be prepared according to the unique advantages of MOFs with different metal centers. Then, we focus on composite SERS substrates based on different MOFs and NMNPs and summarize the application of composite SERS substrates in gas sensing. Finally, the future difficulties and potential possibilities of SERS substrates based on MOFs and NMNPs for gas sensing are discussed.