New naphtho[2,1,8,7-klmn]xanthene and benzo[kl]xanthene-based intramolecular phosphane–borane frustrated Lewis pairs (FLPs) were investigated in catalyzed H2 activation CO2 hydrogenation processes. According to DFT predictions at the B3LYP-D3 level, presence of rigid scaffolds increased P···B distances FLPs lead a remarkable drop energy barrier for (by up 19.2 kcal mol−1, compared parent dimeth...