Possible reaction mechanism for the CO2 cycloaddition to PO catalyzed by multifunctional GO. Reprinted from Carbon, 93, D-H. Lan, L. Chen, C.-T. Au, S.-F. Yin, One-pot synthesized multi-functional graphene oxide as a water-tolerant and efficient metal-free heterogeneous catalyst for cycloaddition reaction, 22–31, copyright (2015), with permission from Elsevier.105