Connecting the Dots: Knitting C-Phenylresorcin[4]arenes with Aromatic Linkers for Task-Specific Porous Organic Polymers

Macrocyclic cavitands having aesthetically appealing architectures and excellent host-guest complexation abilities exhibit a broad range of applications from molecular separation, catalysis, and sensing to drug delivery. However, the close packing of the zero-dimensional (0D) porous cavitands reduces their activity in the solid state. Knitting the macrocyclic cavitands using suitable aromatic linkers may lead to a new generation of porous organic polymers (POPs) where the intrinsic properties of the cavitands can be augmented through interconnected pores in the solid state. Herein, we demonstrate the design strategy of linking the 0D-discrete pores by connecting C-phenylresorcin[4]arene (RN4) through three different aromatic linkers. The flexible azo linkers generate highly dispersible hierarchically mesoporous POP (RN4-Az-OH) exhibiting a remarkable catalytic activity toward metal-free cycloaddition of CO2 with epoxides under solvent-free reaction conditions. Alkyne-based rigid linkers lead to microporous polymer (RN4-OH), which shows CO2 and H-2 uptake at low pressure. The fluorine-rich linkers produce ultramicroporous hydrophobic POP (RN4-F) exhibiting high efficiency toward the charge-specific size-selective removal of organic micropollutants from water. Resorcin[4]arene-derived POPs show superior performance compared to the pristine 0D-porous building units. Thus, "connecting the dots" (0D pores) gives rise to a new interface between supramolecular chemistry and porous organic materials, which can be explored further to address the challenging problems related to green energy and environmental remediation.