3 sentences

1. 他失业后整天无所事事，感到非常空虚。

   tā shī​yè hòu zhěng​tiān wú​suǒ​shì​shì, gǎn​dào fēi​cháng kōng​xū.

   After losing his job, he spent all day idle and felt very empty.

   Source: Dong Chinese Dictionary

2. 如果没有理想，精神生活就会感到十分空虚。

   rú​guǒ méi​yǒu lǐ​xiǎng, jīng​shén shēng​huó jiù huì gǎn​dào shí​fēn kōng​xū.

   Without ideals, one's spiritual life will feel very empty.

   Source: Dong Chinese Dictionary

3. 趁着对方后方兵力空虚，他们发动了突袭。

   chèn​zhe duì​fāng hòu​fāng bīng​lì kōng​xū, tā​men fā​dòng le tū​xí.

   Taking advantage of the enemy's weak defenses in the rear, they launched a surprise attack.

   Source: Dong Chinese Dictionary