# A cucurbit[8]uril-triggered ionic photosensitizer in solution and solid states: selective control of 1O2 and O2˙− generation

## TL;DR

Scientists created a new method using a special molecule to control the production of specific reactive oxygen species and also remove formaldehyde efficiently.

## Contribution

A supramolecular method is introduced for selective control of 1O₂ and O₂˙− generation and HCHO remediation via host–guest assembly.

## Key findings

- The G-I@Q[8] complex enables selective generation of 1O₂ and O₂˙− in solution and solid states.
- The dimeric G-I@Q[8] framework effectively adsorbs and photocatalytically degrades formaldehyde to formic acid.

## Abstract

Selective control of reactive oxygen species (ROS) generation captures the imagination of scientists because of its broad potential applications in photochemical reactions and biomedicine. Herein, we develop a novel supramolecular method enabling selective control of 1O2 and O2˙− generation based on host–guest assembly in solution and the solid state. The cationic guest G-I (Cl− as counteranions) lacks the ability to sensitize ROS but is transformed into an efficient organic photosensitizer through face-to-face dimerization within the cucurbit[8]uril (Q[8] or CB[8]) cavity via host–guest interactions. Although the G-I@Q[8] complex retains an identical assembly structure in both solution and solid-state phases, the differing electron transfer pathways of Cl− counteranions between phases result in selective control of 1O2 and O2˙− generation. This control is readily achievable by employing the host–guest complex as homogeneous or heterogeneous photocatalysts. Importantly, X-ray structural analysis reveals that the dimerized G-I@Q[8] framework exhibits remarkable formaldehyde (HCHO) adsorption capability due to the outer-surface interactions of the Q[8] host, enabling the solid G-I@Q[8] complex to serve as a highly efficient adsorption–photocatalytic platform for HCHO remediation. This study advances our understanding of macrocycle-mediated host–guest assembly in controlling ROS generation and photocatalysts with multiple functions.

A supramolecular approach selectively generates 1O2/O2˙−via host–guest assembly. The dimeric G-I@Q[8] framework adsorbs formaldehyde (HCHO), which is then photocatalytically degraded to formic acid (HCOOH) under blue light or sunlight.