You need to exec to run a sway keybind command
diff --git a/src/apps/personal/sway.nix b/src/apps/personal/sway.nix
index 013828f..2743a80 100644
--- a/src/apps/personal/sway.nix
+++ b/src/apps/personal/sway.nix
@@ -41,7 +41,7 @@
                 "XF86AudioMicMute" = "exec volumectl -m toggle-mute";
                 "XF86MonBrightnessUp" = "exec lightctl up";
                 "XF86MonBrightnessDown" = "exec lightctl down";
-                "${modifier}+Shift+s" = "grim -g \"$(slurp)\"";
+                "${modifier}+Shift+s" = "exec grim -g \"$(slurp)\"";
             };
             keycodebindings = {};
             left = "h";