The enhancement of the surface-enhanced Raman scattering (SERS) property of the plasmonic metal oxide semiconductor nanostructures by controlling their phase, shape, size, and oxygen vacancy to detect trace amounts of organics is of significant interest. In this study, a simple surfactant-free hydrothermal strategy was proposed to fabricate crystalline h-MoO3–x and α-MoO3–x nanomaterials with tunable plasmonic properties. Herein, the crystal phase, morphology, and oxygen vacancy of MoO3–x nanostructures were precisely controlled under suitable synthetic conditions. The plasmonic properties of the as-synthesized h-MoO3–x and α-MoO3–x micro-/nanostructures were controlled by adjusting the residual volume in the autoclaving chamber. In addition, the plasmonic MoO3–x exhibited SERS activity with a detection limit as low as 1.0 × 10–9 M and the maximum enhancement factor (EF) up to 6.99 × 105 for h-MoO3–x , while for α-MoO3–x , the detection limit was 1.0 × 10–7 M with the corresponding EF up to 8.51 × 103, comparable with plasmonic noble metal nanomaterials without a “hot spot”.

In the current scenario of increased pollution and releasing toxic gases by burning petroleum products, switching to natural gas is more promising for reducing CO 2 emissions and air pollutants. Hence, research on Liquefied Natural Gas and Compressed Natural Gas is gaining more value. However, natural gas primarily consists of CH 4 , which has less energy density than conventional fuels. Interestingly, since the CÀ H ratio of CH 4 gas is 1 : 4, it is easily combustible, gives less carbon footprint, and reduces unburnt hydrocarbon pollution. Hence, research on storing and transporting CH 4 has utmost importance, and porous materials are one of the suitable candidates for storing CH 4 . Herein we report the scalable synthesis of highly porous and crystalline covalent organic frameworks for storing CH 4 at room temperature and pressure. Two COFs, namely, Tp-Azo and Tp-Azo-BD(Me) 2 , synthesized in 1 kg at ~45 g batch scale using a Planetary mixer, displayed a maximum BET surface area of around 3345 m 2 /g, and 2342 m 2 /g and CH 4 storage of 174.10 cc/cc and 151 cc/cc, respectively. A comparison of the CH 4 sorption of Tp-Azo and Tp-Azo-BD(Me) 2 COFs synthesized in different batches has a variation of only � 5 cc/cc and shows the consistency in bulk scale synthesis of COFs. The cyclic equilibrium CH 4 adsorption studies showed the COFs are stable with consistent CH 4 adsorption and desorption cycles. The present study is a step towards the scalable mechanochemical synthesis of COFs for gas storage applications.