Regioselectivity is a key point in hydroformylation reactions and its control is still a challenge in heterogeneous 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^{^}Rh clusters to enhance the catalyst lifetime. This work provides an alternative route for developing selective heterogeneous catalysts through steering the catalyst surface microenvironment.