Quantum sensing using molecular qubits is expected to provide excellent sensitivity due to the proximity of the sensor to the target analyte. However, many molecular qubits are used at cryogenic temperatures, and how to make molecular qubits respond to specific analytes remains unclear. Here, we propose a new quantum sensor design in which the coherence time changes in response to a variety of analytes at room temperature. We used the photoexcited triplet, which can be initialized at room temperature, as qubits and introduce them to a metal–organic framework that can flexibly change its pore structure in response to guest adsorption. By changing the local molecular density around the triplet qubits by adsorption of a specific analyte, the mobility of the triplet qubit can be changed, and the coherence time can be made responsive.

Singlet fission (SF) can generate an exchange-coupled quintet triplet pair state 5TT, which could lead to the realization of quantum computing and quantum sensing using entangled multiple qubits even at room temperature. However, the observation of the quantum coherence of 5TT has been limited to cryogenic temperatures, and the fundamental question is what kind of material design will enable its room-temperature quantum coherence. Here we show that the quantum coherence of SF-derived 5TT in a chromophore-integrated metal-organic framework (MOF) can be over hundred nanoseconds at room temperature. The subtle motion of the chromophores in the MOF leads to the enough fluctuation of the exchange interaction necessary for 5TT generation, but at the same time does not cause severe 5TT decoherence. Furthermore, the phase and amplitude of quantum beating can be controlled by molecular motion, opening the way to room-temperature molecular quantum computing based on multiple quantum gate control.