Hairy Conjugated Microporous Polymer Nanoparticles Facilitate Heterogeneous Photoredox Catalysis with Solvent-Specific Dispersibility

Abstract

Substrate accessibility is a key limiting factor for the efficiency of heterogeneous photoredox catalysis. Recently, a high photoactive surface area of conjugated microporous polymer nanoparticles (CMP NPs) has made them promising candidates for overcoming the mass transfer limitation to achieve high photocatalytic efficiency. However, this potential has not been realized due to limited dispersibility of CMP NPs in many solvents, particularly in water. Here, we report a polymer grafting strategy that furnishes versatile hairy CMP NPs with enhanced solvent-specific dispersibility. The method associates hundreds of solvent-miscible repeating units with one chain end of the photocatalyst surface, allowing minimal modification to the CMP network that preserves its photocatalytic activity. Therefore, the enhanced dispersibility of hairy CMP NPs in organic solvents or aqueous solutions affords high efficiency in various photocatalytic organic transformations.

Reticular framework materials for photocatalytic organic reactions

“…[102][103][104] To compare the photoredox activity of various catalytic systems, one of the most popular photocatalytic model reactions is the so-called aza-Henry reaction, which involves functionalizing N-aryltetrahydroisoquinolines (THIQs) and other tertiary amines with various nucleophiles. 105,106 Numerous nucleophiles, including malonates, nitriles, phosphites, and nitro-derivatives, can be used as coupling partners, with oxygen serving as the terminal oxidant. Previously, noble metal complexes such as [Ru(bpy) 3 ] 2+ and [Ir(ppy) 2 (bpy)] + were proven to be active as photocatalysts in aza-Henry reactions.…”

Heterogeneous Photocatalysts for Light‐Mediated Reversible Deactivation Radical Polymerization

“…Many of these alternatives leverage selective or reduced solubility in the reaction medium. For example, “pseudo‐homogeneous” polymeric photocatalysts contain regions which are partially soluble and can help with separation by solvent extraction [190,220,221] . A pseudo‐homogeneous copolymer nanogel was produced by Ferguson and co‐workers [222] .…”

“…Kim et al synthesized photocatalytic conjugated microporous polymer (CMP) nanoparticles that were stabilized via poly(methyl methacrylate) and poly(dimethyl acrylamide) polymer brushes. [190] The catalysts could be recycled five times for an oxidative [3 + 2] cycloaddition reaction with a drop in yield from 69 % to 54 %. This reduction was attributed to the loss of catalyst nanoparticles over 22 cycles of centrifugation.…”

“…For example, "pseudo-homogeneous" polymeric photocatalysts contain regions which are partially soluble and can help with separation by solvent extraction. [190,220,221] A pseudo-homogeneous copolymer nanogel was produced by Ferguson and co-workers. [222] A photocatalyst monomer was copolymerized with N-isopropyl acrylamide and the resulting photocatalytic networks were studied for photocatalytic degradations, oxidation of styrene, and the formation of disulfide bridges.…”

Comonomer effects in vinyl based photocatalytic polymers

“…4–10 However, homogeneous and heterogeneous photocatalysts suffer from significant intrinsic drawbacks, 11–15 including photobleaching, a lack of easy recycling possibilities, limited mass transport to the active center, or poor light absorption. 16–20…”