Intriguing Facets\nof Solution Processable Cross-Linked\nPorous Organic Polymers

ConspectusPorous organic polymers (POPs)\nare organic networks distinguished\nby their highly cross-linked structures and their intrinsic porosity.\nThe growing emphasis on POPs is driven by their exceptional hydrothermal\nstability and diverse application prospects. However, traditional\nmetal-catalyzed high-temperature reactions using rigid building units\nyield POPs in insoluble powder form, posing challenges for processing\ninto different shapes for device integration and optoelectronic applications.\nThe successful fabrication of a soluble porous organic polymer relies\non the employment of specific design strategies and reaction conditions\nto restrict the molecular weight and extensive cross-linking. In recent\ndecades, researchers have been actively exploring various design strategies,\nsuch as limiting molecular weight through hyperbranching and employing\ncontrolled polymer growth strategies, to produce solution processable\namorphous porous organic polymers. However, targeted synthesis for\nspecific applications remains underdeveloped, justifying the need\nfor an in-depth deliberation of currently available strategies and\npossible future avenues. In this context, this Account highlights\nthe advancements in the field of solution processable amorphous cross-linked\nporous organic polymers (SCPOPs), describing diverse design strategies\nand function-led applications. In order to address the challenges\nassociated with the solution processing of amorphous cross-linked\nPOPs, our research group has focused on fine-tuning the noncovalent\ninteractions among the molecular building blocks, the key to achieving\nboth porosity and solubility in the resultant porous polymer. Following\nthis principle, we introduce long alkyl chains as flexible groups\nin the monomer and comonomer units that offer a high degree of rotational\nfreedom and a substantial twist angle. This approach facilitates alleviation\nof the pronounced π–π stacking interaction and\nextensive cross-linking, thereby enhancing the solubility of the porous\npolymer. As a result, the facile interaction between the analytes\nand inefficiently packed polymer chains with aromatic building units\nin SCPOPs opens the scope for fluorescence-based nitroaromatic sensing\nin solution. Further, a stable dispersion of fluorescent porous polymer\nnanoparticles could be an attractive platform for analyte detection\nin water with enhanced sensitivity. The porous nature of the fluorescent\nSCPOPs enables the encapsulation of diverse dye molecules, and controlling\nthe energy transfer efficiency from polymer to dyes results in fluorescence\ntuning, leading to the emission of white light in solution, nanoparticles,\ngel, and a thin transparent film. Furthermore, we demonstrate that\nincorporating alternate donor–acceptor units into the cross-linked\npolymer leads to the optimum band positions for light-driven redox\nreactions, such as photooxidation of benzylamine and hydrogen evolution.\nWe investigated a biphasic catalysis route employing solution-processable\nPOPs to enhance the efficiency while facilitating the recovery and\nreusability of the photocatalysts. As detailed in this review, the\ncomprehensive inspection of the design strategies and potential applications\nof SCPOPs paves the way to delve into designing new processable functional\nporous materials, catering to the need for current sustainable development\ngoals.