Harvesting singlet and triplet excitation energies in covalent organic frameworks for highly efficient photocatalysis

Photocatalysis has traditionally been constrained by selective utilization of either singlet or triplet excited states, limiting efficiency and reaction scope. Achieving simultaneous optimization of both states has remained a challenge. Here we introduce donor-acceptor covalent organic frameworks (COFs) that integrate a dual-state activation strategy. The COFs feature segregated columnar π-arrays, aligned micropores and short donor-acceptor distances. Upon photoexcitation, electron transfer occurs at acceptor units, while energy transfer occurs at donor sites. The porous network also ensures efficient substrate transport to catalytic centres, while intra- and interlayer hydrogen bonding stabilizes excited states, further enhancing photostability and reactivity. This dual-state strategy provides a benchmark for photocatalytic organic transformations, including high turnover frequencies under red-light irradiation, broad-spectrum absorption extending into the near-infrared and operation without metals, co-catalysts or sacrificial donors. By integrating photophysical and structural optimizations, our approach establishes a design strategy that overcomes limitations in solar-driven chemical transformations and broadens the scope of COF-based photocatalysis.