Nanospheres to Nanosheets: Unfolding the Morphological Influence of Microporous Organic Polymers on Micropollutants Removal

Nanoporous organic polymers with distinct morphologies are of immense interest for a broad spectrum of applications ranging from catalysis to molecular separation, energy storage, and energy conversion. However, developing facile and versatile methodologies to obtain well-orchestrated morphologies along with high specific surface area pertinent to a specific application is still a formidable challenge. The design of the task-specific networks can be benefitted through further analysis of subtle variations in the polymerization conditions. Herein, we have critically examined the fabrication of triptycene-based hypercrosslinked polymers (HCPs), exhibiting contrasting morphologies developed through three distinct polymerization routes. Astonishingly, a remarkable variation of nanostructured morphology of irregular aggregates, nanospheres, and nanosheets was noticeable in the resultant network polymers through Friedel-Crafts crosslinking using dimethoxymethane as an external crosslinker, Scholl coupling, and solvent knitting using dichloromethane as an external crosslinker and solvent, respectively. The dramatic role of reaction temperature, catalysts, and solvents driving the formation of specific nanostructured HCPs was elucidated. Mechanistic investigations coupled with spectroscopic and microscopic studies revealed that the 2D-nanosheets of highly porous solvent-knitted HCP (SKTP, S_BET: 2385 m² g^-1) evolved through the hierarchical self-assembly of rigid nanospheres into nanoribbons followed by the formation of nanosheets. We further demonstrated a structure-activity correlation of the pristine as well as post-synthetically sulfonated HCPs for the removal of a gamut of organic micropollutants from water. Solvent knitted triptycene polymer (SKTP) and its sulfonated derivative (SKTPS, S_BET: 1444 m² g^-1) owing to high specific surface areas, excellent dispersity in water, and better accessibility of analytes through 2D-sheet like morphology exhibited ultrafast sequestration (30 s to 5 min) of an extensive array of persistent organic micropollutants, including ionic dyes, plastic components, steroids, antibiotic drugs, and herbicides with excellent recyclability. The current study holds the promise that a delicate control over the morphologies of nanoporous polymers by tuning the fabrication conditions paves the way for the development of advanced porous materials for environmental remediation.