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Main observation and conclusionrnSubstantial progresses have been made toward the development of metal-free catalysts for stereoselective ring-opening polymeriza-tion (ROP) of rac-lactide.Yet the discovery of organic catalysts effective at ambient temperature remains a major challenge.Here,the bifunctional H-bonding catalyst SQ-1 containing a basic tertiary amine and squaramide motif proved to be good candidate for the stereoselective ROP of rac-lactide at room temperature,yielding stereoregular polylactide with controlled molecular weights (up to 21.1 kg/mol) and high tacticity (PiESC up to 0.88).Furthermore,binary H-bonding catalytic system consisting of squaramides (SQ-2 to SQ-6) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) could efficiently promote the ROP of rac-lactide at room temperature within short reaction time.Among them,the most bulky squaramide SQ-2 exhibited the best steroselectivity towards the ROP of rac-lactide without transesterification side reactions during the polymerization process.The resulting polylactides were proved to have con-trolled molecular weights as high as 22.2 kg/mol and narrow distributions (1.10-1.24).