The effectuation of multiple input multiple output (MIMO) systems is severely hampered by mutual interaction between the various antenna configurations. This work depicts a novel billhook-shaped 2-element MIMO array with self-isolation for sub-6 GHz millimeter wave applications. A CPW fed-antenna uses FR4 substrate material with a thickness of 1.6-mm. This MIMO antenna uses defective coplanar ground plane, and spacing between two-patch elements is 3-mm. The two elements are positioned perfectly out of phase to mitigate mutual entanglement. The suggested MIMO antenna of 32 × 67 × 1.6-mm3 size has shown wide 10-dB impedance bandwidth (4–5.71 GHz), maximal gain of 5.63 dB, and a minimal self-isolation of − 27 dB. Additionally, the MIMO diversity metrics like diversity gain ( \({\text{DG}} \cong 10\) ), mean effective gain (MEG < − 3 dB), channel capacity loss (CCL < 0.4 bits/s/Hz), and envelope correlation coefficient (ECC ≪ 0.01) are obtained and addressed. In comparison with mm wave, the proposed antenna for sub-6 GHz frequency waves suffers from lower penetration losses. Consequently, the higher version of it is preferable to install 5G networks in major cities.