Optimization of synthesis conditions, characterization and magnetic properties of lanthanide metal organic frameworks from Brønsted acidic ionic liquid

•Two new two dimensional metal organic frameworks namely {Er2[(C9N2O4H11)3·H2O·Br]Br·Cl}n (1) and {Yb2[(C9N2O4H11)3(H2O)2]Br·Cl2}n (2) were solvothemally synthesized with Brønsted ionic liquid as ligand.•The effects of the reaction conditions to the growth of 1 and 2, such as temperature, reaction solvents, as well as the ratio of solvents were explored.•1 and 2 display good thermal stability and hydrophilicity in this work.•The magnetic measure of 2 shows its antiferromagnetic interaction via the Yb/O-C-O/Yb pathways.