Journal Article asymmetric engineering benzo[1,2-b:4, 5-b′]difuran charge dynamics covalent organic frameworks deep-blue emission deep‐blue emission disulfide bond exciton‐phonon coupling interfacial engineering light-emitting diodes light‐emitting diodes mechanical exfoliation mixed-halide perovskites organic solar cells permittivity perovskite solar cells photocatalytic overall water splitting pure‐halide quantum dots reduced‐dimensional perovskites self‐healing framework spectral stability stress modulation ultrathin structures various‐temperature stability