Abstract: Molecular spin qubits form a potential platform for a broad range of envisioned applications in quantum science, in particular for quantum sensing. One crucial aspects that can limit the applicability of qubits is their decoherence. Understanding the mechanisms underlying the decoherence dynamics of molecular spin qubits is therefore of utmost importance. In this talk, I will present our work on this topic. With a combination experimental data from EPR spectroscopy and computational modeling using many-body quantum dynamics, we identified that pairs and triplets of protons are the main drivers of qubit decoherence. This insight leads to simple design rules for decoherence-robust quantum materials. I will also describe the use of molecular spin qubits in a quantum sensing platform for protein detection.