Regioselectivity is a key point in hydroformylation reactions and its control is still a challenge in hetero-geneous catalysis. Here, we demonstrate that regioselectivity in heterogeneous hydroformylation can be steered by a surface microenvironment around Rh clusters, which are surrounded by K species and confined within silicate-1 zeolites. The K species create a steric hindrance microenvironment on the surfaces of Rh clusters and tune the electronic properties of Rh species, mimicking the Rh-phosphine molecular complex. This microenvironment benefits the linear adsorption of olefins, realizing 83% regioselectivity to linear butyraldehyde with TOF as high as 7328 h(-1) in propylene hydroformylation. Other K species which reduce acidic sites can also inhibit the isomerization of long-chain olefins, thus boosting regioselectivity. The confinement structure can stabilize the K-x<^>h clusters to enhance the catalyst lifetime. This work provides an alternative route for developing selective heterogeneous catalysts through steering the catalyst surface microenvironment. (C) 2020 Elsevier Inc. All rights reserved.