Two unprecedented Sn/Cd-oxo clusters, including non-alkyltin SnII2SnIV2Cd4 and alkyltin SnIV2Cd12, have been constructed using triethanolamine and inorganic or organic tin precursors, respectively. Comparative electrocatalytic CO2 reduction experiments show that the presence of non-alkyl and variable-valent tin centres could greatly improve the catalytic activities.