Exploration of hydrogen-bonded organic framework (HOF) as highly efficient adsorbent for rhodamine B and methyl orange

Inspired by the fascinating merits of hydrogen-bonded frameworks (HOFs) materials such as large surface area, simple preparation and regeneration, and excellent water stability etc., a HOF (PFC-1) was prepared and applied to remove the two organic dyes rhodamine B (RhB) and methyl orange (MO) from wastewater. PFC-1 showed an excellent removal ability towards these two dyes, with a maximum adsorption capacity of 317 mg/g for RhB and 252 mg/g for MO at 298.15K. Both of the adsorption processes can be well fitted with the Langmuir isotherm model and pseudo-second-order kinetic model. Characterization techniques such as PXRD, XPS, and FTIR complemented with DFT calculations were employed to investigate the adsorption mechanisms for RhB and MO. The influence of the pH on the dyes removal was also investigated. The above results indicated that electrostatic attraction, hydrogen bonding and π-π interactions were mainly responsible for the adsorption of RhB onto PFC-1, while van der Waals force largely contributed to the adsorption of MO. Moreover, the calculation of thermodynamic functions suggested that the adsorption of PFC-1 towards RhB was an endothermic process whereas the adsorption for MO was an exothermic process, respectively. Last but not least, PFC-1 could maintain a high removal performance towards RhB and MO even after five cycles, proving its good recyclability and sustainability. Overall, this novel adsorbent has provided new application possibilities of HOFs and suggested their great potential in the area of environmental remediation.