Geometrical frustration conspiring with quantum fluctuations in low-dimensional antiferromagnets has been demonstrated over the past years to lead to novel quantum states in condensed matter. Quantum spin liquids (QSL) on two-dimensional lattices are particularly intriguing, as they are extremely elusive and therefore poorly understood. Triangular lattice antiferromagnets are candidates for a QSL ground state if perturbations to the nearest-neighbour isotropic interactions are present. Here we focus on a novel triangular lattice of Cu2+ trimers in...