CoOx within dealuminated Beta (SiBeta) zeolite developing into ultrasmall-sized Co particles under H-2 or reactant gas is highly efficient for catalyzing direct dehydrogenation of propane (PDH) to propylene reaction. The existence of highly dispersed CoOx species is identified, and the easily reducible CoOx species are confined in the created T-sites (silanols) of SiBeta support. The CoSiBeta catalysts with or without prereduction treatments show similar catalytic performance but different induction periods, implying that the metallic Co formed in situ during the reaction are the active sites. Co in SiBeta zeolite (0.5 wt%) showed state-of-the-art propylene productivity with propane conversion of about 72% and propylene selectivity of over 92% at 600 degrees C, which is far better than that of the other reported Co catalysts and comparable to that of industrial catalysts. This work proves the high catalytic ability and product selectivity of small confined Co particles, as well as providing novel inspiration for the design of low-cost, ecofriendly, and advanced catalysts for PDH. (C) 2020 Elsevier Inc. All rights reserved.