Fully unsaturated all-carbon bifluorenylidene-based polymeric frameworks: synthesis and efficient photocatalysis

Abstract

Conjugated microporous polymers (CMPs) are highly desirable materials with larger surface areas, open channels, and semiconducting properties, which enable them to remove various hazardous pollutants from wastewater via adsorption or photocatalytic degradation. This study reports a novel monomer 9,9′-bifluorenylidene (9,9′-BF) as a versatile building block for the synthesis of CMPs via Yamamoto and Suzuki polymerization. The synthesized CMP-P1 and CMP-P2 with fully unsaturated π-conjugated backbones showed strong visible-light absorption, semiconducting nature, and high porosities. These fascinating properties allow these polymers to efficiently catalyze dye degradation under visible light. The photocatalytic results of both CMP-P1 and CMP-P2 showed a higher degradation efficiency for methylene blue (MB), rhodamine B (RhB), and methyl orange (MO), even better than those of most of the reported polymer photocatalysts. The higher photocatalytic degradation ability of CMP-P1 as compared to CMP-P2 might be due to a higher apparent surface area of 1257 m² g⁻¹ and a narrower bandgap (1.74 eV). Most importantly, these CMPs selectively degraded MB in the mixtures of MB + RhB and MB + MO. The photocatalytic mechanism study indicated the involvement of oxygen and electrons as the main reactive species in the degradation process. The excellent photodegradation results of these new photocatalysts indicate their high potential in water purification applications.