Construction of bonds through the simple,economical,and environmentally friendly mechanochemical(MC)route is of considerable interest in modern synthetic chemistry.Recently mechanochemistry has been efficiently employed to carry out various organic and inorganic transformations,nanostructure formation,construction of metal-organic frameworks(MOFs)and thus has become a good alternative to classical solution-based synthesis.A class of thermally and chemically stable covalent organic frameworks(COFs)were synthesized for the first time via room-temperature solvent-free mechanochemical grinding.1 All these COFs were successfully compared with their solvothermally synthesized counterparts in all aspects.These solvent-free mechanochemically synthesized COFs have moderate crystallinity with remarkable stability in boiling water,acid(9 N HCl),and base(3 N NaOH).Exfoliation of COF layers was simultaneously observed with COF formation during mechanochemical synthesis.Furthermore,such environmentally friendly mechanical grinding strategy was also successfully extended for delaminating already synthesized COFs to covalent organic nanosheets(CONs)and were well characterized via transmission electron microscopy and atomic force microscopy.These exfoliated CONs have graphene-like layered morphology(delaminated layers),unlike the COFs from which they were synthesized.2 Moreover,it has been disclosed that the dynamic covalent bond formation is dramatically accelerated under Liquid-Assisted Grinding(LAG)conditions leading to improved crystalline COFs efficiently at a faster rate and in high yield.3