Surfactant-mediated microwave synthesis of metal organic frameworks for efficient atmospheric water harvesting

Metal organic frameworks (MOFs) have emerged as promising candidates for atmospheric water harvesting due to their high porosity and tunable functionality. Among diverse MOFs, MOF-303 has demonstrated excellent water adsorption capacity, rapid desorption kinetics and structural stability. Nevertheless, its practical application is still limited by the time-consuming synthesis process and difficulties in morphological control. To overcome these challenges, a surfactant-mediated microwave-assisted strategy was proposed. Compared to conventional heating methods, microwave irradiation reduced the reaction duration from 24 h to 1 h with a 13% increase in product yield (from 76 % to 89 %). However, the accelerated nucleation under microwave irradiation resulted in smaller crystal dimensions (from 50 nm ± 10 nm to 35 nm ± 10 nm), therefore inducing severe particle agglomeration. To mitigate this morphological drawback, systematic investigations were conducted to evaluate the effects of surfactants’ species on crystal growth. Among the selected surfactants, poly(sodium- p -styrene sulfonate) (PSS) was identified as an effective morphology-directing agent, achieving uniform crystal sizes with improved monodispersity through preferential adsorption on specific crystallographic planes of the metal-organic framework. Subsequent optimization of synthetic conditions, including temperature (120−160 °C), reaction time (15 min−1 h), and surfactant concentration, yielded metal organic frameworks-303 (MOF-303) with a yield of 96.37%, with particle uniformity of (35 nm ± 10 nm) and predominantly blocky crystal morphology. Water adsorption measurements confirmed that the surfactant-modified MOF-303 retained comparable performance to the surfactant-free counterpart, with a maximum capacity (water/MOF) of 0.214 g·g −1 at 35% RH. This study establishes a scalable and tunable synthetic protocol for MOF-303, providing critical insights into microwave-accelerated crystal engineering.